Victor Zlotnicki, Ocean Physicist

The Jet Propulsion Laboratory is best known in the public imagination for its daring explorations beyond Earth and the frontier-defining missions it has led to Mars, to the outer planets, and to interstellar space, among others. In its more recent history, JPL has also become a world-leading research institution for its focus on Earth and its use of satellites to study our planet's composition, and especially, its changing climate. If a large part of JPL's extra-terrestrial mission is driven purely by curiosity about our solar system and the universe - and pushing the boundary of what is possible in engineering, what the Lab's satellites tell us about Earth are vitally important if we are to understand and adapt to global warming.

In the career of Victor Zlotnicki we have a microcosm of JPL's embrace of ocean physics, ice melt observations, and what these phenomena can tell us about climate change. Since his arrival at JPL in the 1980s and his leading participation in Earth science missions that utilized satellites equipped with cutting-edge sensors to analyze the world's oceans and ice sheets, Zlotnicki's research has had a formative impact across a broad range of disciplines. By the mid-1990s, as the scientific community was coalescing around the reality and impact of climate change, JPL was well positioned to lead the all-important efforts for monitoring rising ocean levels and the melting of ice sheets in Antarctica and Greenland. These developments received a major boost under the directorship of Charles Elachi in the early 2000s, who drew on his own expertise in radar and who recognized the import of putting JPL's capabilities in the service of what is arguably the most pressing need in scientific observation.

In the discussion below, Zlotnicki reflects on his family's Jewish-Argentine background and his upbringing in Buenos Aires, the opportunities that led him to pursue a unique joint program in marine geophysics at MIT and the Woods Hole Oceanographic Institution, and his early recognition that NASA, and eventually JPL, offered a perfect environment to pursue a career in ocean physics. Newly retired, Zlotnicki provides key perspective on JPL's increasing involvement in Earth science, and he expresses optimism in its ongoing leadership to understand the dynamics of oceans and their role in climate change.

DAVID ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It is Friday, June 2nd, 2023. I am delighted to be here with Dr. Victor Zlotnicki. Victor, it's wonderful to be with you. Thank you so much for joining me today.

VICTOR ZLOTNICKI: Thank you for inviting me.

ZIERLER: To start, would you please tell me your most recent title and institutional affiliation?

ZLOTNICKI: JPL, Assistant Manager of the Earth Science Section, Program Manager for Climate Variability, and Principal Scientist. And I retired four weeks ago.

ZIERLER: Congratulations on your retirement. What's it like for you now?

ZLOTNICKI: Well, it's more relaxed, and I'm beginning to have too much time in my hands. But, that's not going to last.

ZIERLER: Do you see this as a true retirement from science? Do you intend to stay active with the literature? Are there any ongoing research projects you want to pursue?

ZLOTNICKI: To be honest, probably not.

ZIERLER: Is there an emeritus designation or equivalent at JPL? Do you have any sort of opportunity just to stay engaged if you'd like?

ZLOTNICKI: Actually, I do. There is no emeritus position; there is something close to emeritus for senior research scientists, where they come back with no pay. It's not really an emeritus position but it's the closest that JPL can do. There is another thing called the Interim Employee Program, whereby you come back as an employee, less than 50% time, as an hourly employee. You charge by the hour that you work, and it must be less than 50% time, so that you don't receive benefits from JPL—no retirement, no medical, and so forth. I do have some work from NASA headquarters that they asked me to stay on, so I will be coming back as an IEP.

NASA Leadership in Ocean Physics

ZIERLER: What is the discipline or the title that would best serve as an umbrella for all the things that you've worked on in your research career?

ZLOTNICKI: Ocean physics. And a little bit of geodesy.

ZIERLER: How far back does that term go? Where would we see professors of ocean physics, departments of ocean physics? How old a field is it?

ZLOTNICKI: The field exploded in the U.S. with Second World War. It exploded because a bunch of very bright scientists predicted wave conditions for disembarkments, for coastal attacks like the Normandy attack, and they saved many soldiers' lives. After that, in the U.S., the Office of Naval Research could see no wrong with ocean physics. All a scientist had to do was go and ask for some more money, and you would get it. Ocean physics of course precedes that. Harald Sverdrup was a famous Norwegian oceanographer from the early 1900s who later came to the US. In other European countries, there were professors of ocean physics going back to the beginning of the century. We trace the first ocean physics observations to the Challenger expedition of the British Navy back in 1872.

ZIERLER: I assume ocean physics must be very interdisciplinary in its nature. What are the kinds of fields of expertise that are required to go into ocean physics?

ZLOTNICKI: Oceanography is very interdisciplinary; ocean physics is not. For example, in order to get a degree in oceanography at the Scripps Institution of Oceanography, which I did not attend, you had to pass exams—it's my understanding, so it is secondhand—in ocean biology, ocean geology, marine geophysics, ocean chemistry, and ocean physics. Where I studied, which was the joint program between MIT and the Woods Hole Oceanographic Institution, you just had to pass within your field. As it turned out, I did not study ocean physics at MIT/Woods Hole, but rather marine geophysics, which is more concerned with the mountains and the sediments and the plate tectonics, those areas of oceanography. Ocean physics is more concerned with the physics of rotating flows, like the atmosphere and the ocean. We are in a spinning Earth; that causes all the fluids to rotate, and those have special qualities that require a fair amount of physics.

ZIERLER: I wonder if you've ever thought about the road not traveled. If you had pursued an academic career at a university, if you were a professor of ocean physics, as opposed to a manager at JPL, do you think you would have pursued more or less the same kind of research, or just by being at JPL, that really directed the kinds of things that you worked on?

ZLOTNICKI: No, I would have done differently, I am sure. When I was a grad student, I wrote my thesis on a combination of satellite and in situ data, and I decided that I really probably wanted to be working for NASA. So I decided very early on that I was not going to pursue an academic career and I was going to work for NASA. I do have an anecdote related to that, though. One of the classes I passed in grad school was a seismology class, and my professor, whose name was Keiiti Aki, a very famous seismologist, got me into his office to review my term paper. He looked at it, and he said, "First sentence—‘earthquakes happen like so and so'—wrong! Totally wrong!" I said, "Wait, I didn't invent it. I read the paper by Smith and Johnson, and the conclusions were such and such, so that's the basis for my first sentence." "Oh. Second sentence—‘plate tectonics does not cause earthquakes'—wrong! Totally wrong!" "Wait a minute, I did not invent it." And you are beginning to get the hang of it. So after about 15 minutes of that, he said, "You should go into research. Don't work for oil companies."

ZIERLER: [laughs]

ZLOTNICKI: So—I got the encouragement from Kei Aki to go into research—

ZIERLER: [laughs]

ZLOTNICKI: —but I decided I was going to work for NASA, early on.

ZIERLER: What was compelling about NASA? What was NASA doing at the time that directed your ambitions that way?

ZLOTNICKI: Most of the new things that were going to be coming into oceanography, I felt, were going to be improved by satellite data. I don't know exactly how I reached that conclusion. Because when you are in grad school, you don't really think of the technology—or at least in my environment, we did not think of the technology as a driver; we thought of the science questions as drivers. The science questions drive everything else. To this day, at NASA, we drive missions with science questions. It is true. But it is also true that new technologies open up new science questions. Always. That was not as obvious when I was a grad student, but I had the inkling that those new discoveries would come from satellite observations. And many of them did.

ZIERLER: For our broader audience that might more closely associate JPL with Voyager and interstellar space and Mars exploration, what role does ocean physics play in the overall mission of JPL?

ZLOTNICKI: I would like to give you a little bit of history of that. I came to JPL in 1983. In 1978, JPL had launched a satellite called Seasat, to observe the oceans. I can tell you more about Seasat later on. But before Seasat, the only Earth science at JPL was some geology. There were a bunch of geologists doing Earth as a proxy for planetary geology. So there was no Earth science, per se. It was only as a help in studying planetary geology. Seasat was the one that really turned that around, because it observed Earth's oceans for their own sake, with a bunch of different instruments. At the time there was a director for Research and Technology called Don Ray, who did not really like JPL doing Earth science, and oceanography in particular. That was for Goddard SFC to do. But other voices at JPL, including Mous Chahine, who became the chief scientist of JPL—at the time, he was head of the Science Division—overrode Don Ray. So, that's a little bit of the history of Earth science at JPL. There was only geology before Seasat. The geology was for the purpose of support planetary. After Seasat was the beginning of studying Earth science in general, even though Seasat was only for ocean physics and biology.

ZIERLER: I'm sure you've heard the history about how Caltech's Seismo Lab was really not involved in the plate tectonics revolution of the 1960s because it did not have an oceanography department. Do you think that JPL's embrace of ocean physics and oceanography in some ways was meant to fill that gap?

ZLOTNICKI: I don't think so. I think it's totally independent. It was a confluence of a particular person at NASA headquarters called Stan Wilson, who had been in the Navy, and he went to NASA to look after oceanography in general, and he began pushing for JPL to get more involved, and therefore provided the funding that JPL used to hire a whole bunch of oceanographers in the late 1970s in order to support this Seasat mission. So, JPL didn't have any ocean scientists at all, and a bunch were hired—one in glaciology, cryospheric science, one in ocean biology, a couple in ocean physics, none in marine geophysics, and none in ocean chemistry, because we cannot do ocean chemistry from space. Those were the nucleus around which Earth science got started at JPL. But I think it had nothing to do with the Caltech Seismo Lab not being involved in plate tectonics.

ZIERLER: Your overall research, would you say it was exclusively interested or focused in basic science, fundamental research? Or were there aspects that were really more applied, where there was a societal issue or a technology that you were working on?

ZLOTNICKI: Part of what is expected of a JPL scientist is to demonstrate the usefulness of our data, of our satellite instruments, in order to do regular, real science advances in a particular field. So, I embraced that aspect of the science. What I can claim as having done was applications of radar altimetry to ocean circulation studies, and applications of gravity measurements from space, in particular GRACE, to ocean studies. I wrote the first paper on a direct application of GRACE data in ocean studies. So, it was applied, not in the sense of applied for the benefit of society, but in the sense of an application of satellite data to ocean circulation studies. You could view it a little bit as opportunistic, rather than directed by the science question that had been posed before.

An Ocean Physics Perspective on Climate Change

ZIERLER: Given the importance of oceans for understanding climate change and global warming, did you ever get involved in that? More generally, what might an ocean physicist add to our understanding of climate change?

ZLOTNICKI: Let me start with the data and then continue on. This Seasat mission triggered another mission called TOPEX/Poseidon, which also measured the height of sea level. TOPEX/Poseidon engendered another mission called Jason-1, which begot Jason-2, which begot Jason-3. Now, the Europeans really have taken over that series, except for the current SWOT mission. So, that sequence of missions built a time series of rising sea level that is unequaled, and that could not have been done with tide gauges. In addition to showing us that sea level is going up, and is going up a little faster now that 20 years ago, and is going up the way we can predict it with climate models, that allows us to estimate how much heat the oceans are absorbing from the atmosphere and how much heat is released in other places back to the atmosphere. You can do that by combining the satellite data with in situ data that penetrate the oceans and measure temperature and salinity and so forth. So, the connection to climate change is directly through sea level, and the estimate—it's called the Earth energy imbalance. The Earth energy imbalance is the amount of energy that comes in minus the amount of energy that goes back out. More comes in than goes out, so we are absorbing a certain amount of that, and most of it is absorbed by the oceans. That's the part that is causing sea level to go up and that is our link to climate change.

ZIERLER: What are some of the big takeaways in your study of ocean physics and climate change? What have we learned so far? What are some of the open question marks?

ZLOTNICKI: The open question marks are much more on the very short spatial scales right now. This global sea level rise is a large-scale phenomenon. It affects the coasts, of course, but we tend not to observe that. We did not observe that until now, when SWOT was launched. SWOT measures very short length scales of ocean circulation, on the order of a few kilometers. On that scale, there are upwellings that happen where water masses meet which bring up heat from the bottom, which bring up nutrients for the fish. I don't know whether I'm explaining this properly but the current frontiers, for at least the satellite observed oceans, are in short scales, the shorter scales of the circulation, rather than the global sea level rise or the global sloshing of the oceans.

ZIERLER: In the quest to mitigate climate change, either through geoengineering or other measures, what is an ocean physics response? What are the kinds of things that we can harness from the oceans to slow the pace of global warming?

ZLOTNICKI: [laughs] This deals much more with ocean chemistry than with ocean physics. Ocean physics basically refers to the transport of heat, momentum, and particles, from one place to the other, and releasing them back to the atmosphere. That's the essence of ocean physics. It's a crude explanation, but it's fairly accurate. Ocean chemistry deals with the composition of the oceans, the chemical composition of the oceans. The mitigation part comes by having the oceans absorb more carbon from the atmosphere. Much of that exchange of carbon happens at the high latitudes, at the high Southern latitudes actually, in the Southern Ocean. There have been experiments seeding the oceans in a way as to accelerate the absorption of carbon, look up ‘ocean fertilization' in Wikipedia. That's one way in which oceanography—not ocean physics per se but oceanography in general—is helping understand the mitigation part of climate change. Another one is through what I explained about heat uptake. If we see that some measures that are being taken in other environments—not necessarily in the oceans—have an effect on the Earth energy imbalance, which we can measure in the oceans, then we will know that those measures are effective.

ZIERLER: Let's take it all the way back to the beginning now. Let's go back to Argentina. How many generations back was your family there?

ZLOTNICKI: My father is first generation. My mother is second generation. Was. Were.

ZIERLER: Where is that in relation to World War II?

ZLOTNICKI: Both families came to Argentina just before World War II. My father survived World War I in Poland. He was a teenager back then. His description of Poland was the Russian Army paraded through the town, and when the last Russian was out, the German Army paraded through the town, and when the last German was out, the Russian Army came back. And the German Army expropriated the brass knobs from the doors for cannon, but left receipts, whereas the Russian Army also expropriated, but did not leave receipts. He then became an illegal alien in Germany after the War, because Germany was totally destroyed but Poland looked much worse. So, he snuck into the border with Germany and began working in Germany, and then he went around Europe a little bit, and finally came to Argentina in the 1930s. My mother's father came to Argentina in 1905, from Ukraine, from essentially Ukraine. Those were real men. He worked for five or seven years and then brought his wife who had been left behind. Then he worked for another five or seven years and brought his brother and the rest of the family. Then he opened a general store in a town called Pigue, in the province of Buenos Aires.

ZIERLER: The father's side of the family in the 1930s, was one of the reasons to get out the rising tide of anti-Semitism?

ZLOTNICKI: I think it was as much economic opportunity as something else. He felt the anti-Semitism in Poland. He felt it in France. He felt it everywhere, but probably did not appreciate what was coming. But I think his opportunity to come to Argentina was as much driven by economic opportunity as escaping from some rising tide that he did not perceive as threatening just yet. Because it was a little early in the process of Nazification of Germany.

ZIERLER: Do you know on both sides of your family what the size of the Jewish community in Argentina was, when they arrived?

ZLOTNICKI: No. [laughs] Yeah, to be honest, no, I don't.

ZIERLER: Where did they both land, your mother's and father's families?

ZLOTNICKI: My father landed in Buenos Aires, in the capital. He had been a tailor. He had learned tailoring in Poland as a child, and he had supported himself throughout his bumming through Europe, as a tailor. He was very proud that he had worked for Maison Lanvin in Paris. In Argentina, he ended up in a sweatshop, basically, sewing military uniforms, as he told me. Then one year he went on a vacation for seven days, which was what they gave him, and he was really enjoying himself on that vacation, so he stayed another couple days and sent a telegram saying, "I am sorry. I fell sick. I cannot come back immediately." He received a telegram back saying, "Don't bother ever coming back." So, he decided he would never again live under a boss, and he became a salesman. Fortunately, that worked fine. On my mother's side of the family, they went directly to the countryside, and my grandfather, my mother's father, was a farmhand, basically, for a few years, until he made enough money to open a store. Then he enlarged the store, and he became a storekeeper, of a general store.

ZIERLER: Where did your parents meet?

ZLOTNICKI: In the city of Buenos Aires.

ZIERLER: What language did they speak with one another? Where they fluent in Spanish already?

ZLOTNICKI: Well—[laughs]—my mother was of course born in Argentina. She was a school teacher, and so she was most definitely not only fluent in Spanish but very competent. My father spoke Spanish just like a Brooklyn Jew speaks English.

ZIERLER: [laughs]

ZLOTNICKI: —same accent, just different words. So, when they didn't want me to understand what they said, they would speak Yiddish. Which of course made me learn it very quickly, and so I quickly figured out what they were saying.

ZIERLER: [laughs]

ZLOTNICKI: When there was a normal conversation, they spoke Spanish. Even though, again, my father's Spanish was a little broken up.

ZIERLER: Growing up, was your family Jewishly connected? Did you belong to a synagogue?

ZLOTNICKI: We were of the—go a couple times a year for Rosh Hashanah, Yom Kippur, and maybe one more. Maybe Passover. Pesach. Proud to be Jews, proud to be different, but not very observant.

Argentine Roots

ZIERLER: What neighborhood did you grow up in, in Buenos Aires?

ZLOTNICKI: Well, do you know Buenos Aires?

ZIERLER: I've visited. I know it's a huge city. I know there's many different places.

ZLOTNICKI: Yeah. My neighborhood was called Almagro, which my mother—but it was two blocks from another neighborhood called Caballito. It turns out that Caballito is a little bit higher social standing than Almagro, so my mother used to like to say that she lived in Caballito, rather than in Almagro. But yeah, I grew up in Almagro. [laughs]

ZIERLER: [laughs] What kinds of schools did you go to, growing up?

ZLOTNICKI: I went to my neighborhood elementary school. I tried for a couple years to go to the Jewish school before my Bar Mitzvah, but it only lasted two years and I don't know why my parents took me out. That was it. For high school, fortunately for the wrong reasons, I applied to the most prestigious high school in Buenos Aires. I can tell you what the wrong reasons are.

ZIERLER: Please!

ZLOTNICKI: I was going to go to my neighborhood high school and that was it, but one day I met a former classmate of mine who was one year ahead of me in grade school, and he was very neatly dressed. He had a lapel pin from the high school. He pointed out that this high school, as opposed to—my neighborhood high school was a boys-only high school. The prestigious high school was actually co-ed. And so, he explained all about how nice the girls were. And so that combination of the lapel pin and the girls made me apply for this other high school called Colegio Nacional de Buenos Aires. And I made it in.

ZIERLER: Were you always interested in science?

ZLOTNICKI: Yeah. In general, I did much better in physics, chemistry, botany, and biology, and math, than I did in, say, geography, where I had a hard time memorizing so many rivers and lakes and cities and things like that.

ZIERLER: When it was time to think about college, what were your options? Did you know you wanted to stay close to home?

ZLOTNICKI: Yeah. When I decided to go to college, I knew I wanted to study either physics or engineering. It was simple. But I had a teacher in high school who had a master's degree in physics, but he was a professor of math. I asked him about studying physics versus engineering, and he said, "Do you like buses?" I said, "What?" "Do you like buses?" I said, "Not particularly. Why?" He said, "Because I take a bus to come and teach here for two or three hours, then I take another bus and go to another school where I teach for another three hours, then I take a third bus to a third school where I go and teach for another few hours. So, if that's the life you want, get a degree in physics, because that's the only physics you can do in Argentina, teaching high school. If you want something else, go to engineering." So, he convinced me to start in the School of Engineering [laughs] for not very good reasons. But anyway, yes.

ZIERLER: Do you think the background in engineering served you well?

ZLOTNICKI: Yeah. I studied land surveying and geodesy, geodetical engineering in Argentina, and it helped me. It helped me quite a bit with what I did afterwards. They had a strong background in physics and math and so forth, so it helped me. I think of it as an undergrad. It was like an undergrad in engineering.

ZIERLER: Did you work after college, or did you immediately pursue graduate school?

ZLOTNICKI: I got a job at the Navy Hydrographic Office, in Argentina. That was at a time when there was already a dirty war going on, and this was a Navy facility. So I still remember, to get into the Navy Hydrographic Office, they were very suspicious of my father being Polish, because they thought, "He's Polish, he's Jewish, he must be a communist." The commander of the division where I was going to go in—I was invited there by my professor at the university, but the commander, who was a captain, called me to his office and said, "Look, I vouched for you, for your father, and for your whole family. If you do well, I will be delighted. And if you don't, I will be the one to shoot you." I said, "Yes, sir." [laughs]

ZIERLER: [laughs]

ZLOTNICKI: And that was it. Anyway, we got along just fine with him. So, I did work there for a couple of years. My applying to grad school abroad was very serendipitous. I used to do aikido, which is a Japanese martial art, and I had a classmate who was the son of the French cultural attaché, and we were very good friends. One day he says, "You know, my mother has all these scholarships to go to France that go unused every year." I said, "But why would they take me? I am nobody. I'm not necessarily the best student in the university," and whatnot. He said, "Well, but she has these scholarships that go unused, which means if you apply, you have a better than half chance of getting it. Because otherwise they go unused." So, being Victor, I said, "Well, if I can go to France, where else can I go to?" I looked around and I decided to apply to the U.S. rather than to France. I applied to MIT, to Columbia University, Scripps and to Oregon State. Scripps didn't take me. Oregon and MIT took me. So, that was it.

Marine Geophysics at MIT

ZIERLER: Was it oceanography or ocean physics that you were specifically focused on?

ZLOTNICKI: Actually, it was marine geophysics, which is more the plate tectonics part of oceanography than the ocean circulation part of oceanography. The reason I applied in oceanography was that I was working on that at the Hydrographic Office, therefore I had a taste of what the field was like. And, it promised travel. I had not left Argentina until then, anywhere, to go anywhere. So, it promised physics and math, and travel. That was it. Those were the ingredients that attracted me.

ZIERLER: Did you apply to MIT knowing that you would work at Woods Hole? Do you apply to both programs at the same time? How does that work?

ZLOTNICKI: It's a joint program between MIT and Woods Hole, so I applied to the joint program.

ZIERLER: Woods Hole is an independent institution; it's not part of MIT?

ZLOTNICKI: Correct. Woods Hole Oceanographic Institution is an independent institution. They do research in all aspects of oceanography, just like Scripps Institution of Oceanography here in California. But, as opposed to Scripps, which is part of the UC system, Woods Hole is totally independent. But they (MIT and WHOI) joined forces some years back. The idea was that the basic math and physics and so forth would be taught by MIT, and the advanced oceanography would be taught by Woods Hole. In reality MIT had its own strength in ocean physics and marine geophysics and even marine chemistry, so it didn't work out the way they had originally planned. But yes, Woods Hole is an independent institution; the program is joint.

ZIERLER: Before starting the program, how was your English? Had you traveled to the United States before?

ZLOTNICKI: No, I had never traveled to the U.S. I had learned English in Argentina. That's another thing that triggered my trying to come to the U.S. I spoke French, too, actually. I do; not as well now as my English. There was a visitor that came to the Navy Hydrographic Office from the U.S., and since I spoke reasonably fluent English, they asked me to be his host. I take him to see one captain, who had studied at Woods Hole, for a year. He had been on a leave for a year to study at the Woods Hole Oceanographic Institution. I thought, "Wow, this guy has studied already at the place I would like to go." It turned out that this captain spoke to my American guest a bit as Tarzan speaks. And so, I thought, "Jeez, I speak English much more fluently than this captain, and he survived a whole year in the U.S. How can I not survive in that environment?" So that gave me encouragement that my English was good enough.

ZIERLER: [laughs] Victor, physically how much time did you spend in Cambridge, and how much were you on the Woods Hole campus?

ZLOTNICKI: Eighty percent time at MIT, twenty percent at Woods Hole.

ZIERLER: What were the kinds of things that would bring you to Woods Hole?

ZLOTNICKI: We had classes at Woods Hole. My advisor was really an MIT professor, rather than a Woods Hole scientist. My main advisor was at MIT. We took certain classes in Woods Hole usually during the summers. The first three years, every summer I spent it at Woods Hole. In the last few years, I just spent all my time at MIT.

ZIERLER: When you started the program, what were some of the big ideas in oceanography? What were people excited about in the early 1980s?

ZLOTNICKI: It depends on the people. [laughs] Science is done by humans, and they do disagree on what are the important questions. My advisor's name was Carl Wunsch; he's alive and well. Back then, he was steeped in the classical oceanography that was most interested in the general circulation of the oceans, in the large scale circulation and large-scale transport of heat, large-scale transport of properties. There had been some work in the years before on something called mesoscale—mesoscale physics—which is 100 kilometers to a few hundred kilometers problems. And interest in El Nin~o was developing. But it looked like most of the work back then was on the large-scale ocean physics. There was very little interest among physical oceanographers about sea level, about tides. They were all problems that generated no interest in the physical oceanographic community—both sea level and tides because they were deemed solved problems from the physics point of view even though not from the observational. It turned out that over the subsequent years, the whole view of the field changed, so now, sea level is considered an important problem [laughs] in ocean physics. Tides were actually solved through radar altimetry, and that generated a whole effort to understand how much tides dissipate energy from the Sun-Moon system. That's where the field was back then in the 1980s.

ZIERLER: What were some of the key technologies that were driving the field forward when you were a graduate student?

ZLOTNICKI: Current meters. The big revolutionary thing was current meters. We basically had instruments like bathythermographs and expendable bathythermographs that measured the temperature in the upper 500 meters. We had CTDs, conductivity temperature depth, that measured temperature and salinity all the way to the bottom of the ocean. We had bottles that capture a chunk of water and you can measure the temperature, the salinity, the chemical composition, the bugs living in it, and so forth. And we had some experiments, very few, on air-sea interactions, the fluxes of heat and momentum and carbon and so forth near the surface of the ocean. There were stations. There were turbulent exchange measurements at the surface. That was, as far as I remember, the state of the technology.

ZIERLER: What about computers? Was oceanography or were ocean physicists already embracing computers when you were at MIT?

ZLOTNICKI: Yeah. If you remember, not in ocean physics but in atmospheric science, there was a famous numerical experiment by Ed Lorenz at MIT, just a few years before I arrived. Ed Lorenz had programmed a computer to predict weather. He had written the program in such a way where—or his programmer wrote the program in such a way that, because of the primitive computers, it had to be entered a couple times. The initial values and the program had to be entered, run, then entered again, run, and so forth. He discovered that even though they would enter what they thought were the same initial values, the computer would evolve differently the weather. Instead of blaming it on the computer, he realized that the equations were very sensitive to very small changes in the initial values. So, if they failed to put 27 significant digits—I'm making up the number—but if they put only 24 significant digits in the initial value, and they dropped the last three, the computer would give a different answer, but very different answer. That's what led him to the theory that became known as the Butterfly Effect, that a very small change in one location can produce huge changes in another location, because the equations are nonlinear, so initial changes grow exponentially. It gave birth to chaos theory. So, computers were used. I used computers. Not as brilliantly as Ed Lorenz, but they were used. But they were very primitive computers. When I came to JPL—that was of course after I finished my PhD—I was proudly given one megabyte of disk space!

ZIERLER: [laughs]

ZLOTNICKI: As a reminder, your cell phone probably has 128,000 megabytes of memory, not of disk space. Well, of memory disk. And that's in your phone. So, yeah, I was proudly given one megabyte of disk space.

ZIERLER: [laughs] What aspects of your graduate study were laboratory-based, and did you ever have the opportunity for field research, ocean-going research?

ZLOTNICKI: I did, actually. As soon as I came to MIT, within three months I was on a boat going to Iceland. I was in the Marine Geophysics program, so instead of measuring ocean circulation properties, I was measuring heat flux through the sea floor. The way we did that was by dropping a—it's called a piston corer, a large tube with a very heavy head, that plunged into the ocean and measured the gradient of temperature and brought back sediment. Through the conductivity of the sediment and the gradient of temperature, we measured how much heat was going up into the water from the ocean floor. That was my job during that campaign. I had a great time. The other students and I rented a car and we visited Iceland, and we had a great time. Then, my advisor at the time—who was not Carl Wunsch; it was another professor, John Sclater—said, "Okay, next year, you are going to go to the Weddell Sea and measure heat flow by yourself." I said, "But wait a minute, I just went on a campaign where I was the flunky. I am not sure I can do that by myself." He said, "Victor, if you want a degree from MIT, you're going to go, [laughs] you're going to measure it by yourself, and you're going to come back with useful results. Your degree depends on that." [laughs] So I learned. I got my degree eventually.

ZIERLER: Tell me about the interplay of experiment and theory in graduate school.

ZLOTNICKI: We had theoreticians like Joe Pedlosky and others who were vaguely interested in—they were interested in experiments. But my favorite book was really Adrian Gill's, which was a very good experiment-based theoretical explanation of the observations. The better oceanographers are always the ones who could get an observation, get the theory behind it, and publish a paper that combined theory and observations. We knew that. There were observational-only oceanographers who basically measured things, said, "This is what the ocean does." I remember a famous observational oceanographer called Klaus Wyrtki, who wrote a very good paper that became part of the beginnings of El Nińo, and talking about equatorial currents, and saying, "This will give theoreticians something to worry about for a while." Some words to that effect, in the paper. So, he couldn't explain it theoretically. He was a good observationalist, and he did it. Then there were at the other extreme theoreticians like Joe Pedlosky, who seldom went to sea, and did what they did in an office. I had the good luck in Marine Geophysics to meet Dan McKenzie, a famous British geophysicist. He was a very good combination of observation and theory, a very good example for me.

ZIERLER: Tell me about the process of developing your dissertation research.

ZLOTNICKI: The problem was given to me when I changed advisors. In the beginning, my advisor was John Sclater, and I decided that for my thesis I wanted to do something else. So, I shopped around, in a sense, around MIT, looking for topics that various professors had. This professor, Carl Wunsch, had a very nice topic which combined physical oceanography and marine geophysics. Because sea level is a combined problem. Sea level to first order reflects the gravity field of the Earth. And only after the—so it has mountains and valleys that reflect the gravity field of the Earth, and only the small difference between the actual sea level and those gravity-induced mountains and valleys, called the geoid, is where the physical oceanography is. Anyway, he had what to me was an interesting problem. What I did was different than my roommate, my friend at Woods Hole—not roommate; officemate—at Woods Hole. His name is Alan Chave. He's a senior scientist at Woods Hole now. Alan knew what he wanted to do for a thesis since the moment he entered. It helped that his father was a professor of oceanography so he knew the field. He knew how to do it. And he shopped around for an advisor that would accept his idea of a thesis. I did it the other way; I shopped for an advisor whose idea I liked. That's how I came up with my thesis topic.

ZIERLER: What were the big questions that drove the research for you?

ZLOTNICKI: What I just briefly described, which is, what are the small differences between the marine geoid and the actual surface of the ocean? How do they reflect ocean physics, and how can you separate them?

ZIERLER: In thinking about sea level rise, was anybody thinking about climate change, when you were a grad student?

ZLOTNICKI: No, back then, as I told you, sea level rise was not a topic of interest in ocean physics because they thought that the problem involved—it doesn't really involve much physics, to be honest, in terms of rotation, and conservation of planetary vorticity, and transport of vorticity and things like that. It doesn't have turbulence, which is another topic of interest these days. So, it doesn't have the fundamental physics that people were interested in at the time. So, no, they didn't care about sea level rise. They cared about the general circulation of the ocean back then.

Ben Franklin and the Gulf Stream

ZIERLER: What were your principal conclusions with your thesis? What did you find?

ZLOTNICKI: I demonstrated how to separate the two components in the North Atlantic. That was my first—my basic conclusion.

ZIERLER: Which told you what? What is the takeaway?

ZLOTNICKI: The takeaway is how much—on the long term time average—let me explain one thing. Did you know that Ben Franklin made a map of the Gulf Stream?

ZIERLER: No!

ZLOTNICKI: Okay. So let me tell you that story. I was totally uninvolved, at the time. [laughs]

ZIERLER: [laughs]

ZLOTNICKI: Ben Franklin, among his various jobs, had the job of postmaster general. As postmaster general, he was in charge of making sure that the letters got to England, and came from England; from Europe, and came back from Europe. He noticed that the letters going to Europe took a lot less time than the letters coming back from Europe. He figured out it had something to do with ocean currents because they were transported by ships. He had a cousin called Tim Folger, who was a fisherman in Cape Cod. So he went to his cousin, and he said, "Do you know of any currents here that could explain this problem?" He said, "Yeah, sure. We call it the Gulf Stream. There's this current that goes like so. We've tried to warn the captains of mail ships and so forth about this current, but they won't listen to mere fishermen. They are seasoned captains from Merchant Marine, so they don't listen to fishermen." Ben Franklin said, "How do you recognize the current?" He said, "Because it's warmer than the water around it. When you are in the current, you have warmer water." He said, "Well, would you take these thermometers and put them in the water and plot where you are when you measure it?" So his cousin engaged the other fishermen, and they all went out and measured temperatures in the water, and made a map of the Gulf Stream back in 1760-something. I don't remember the date, but it's the 1700s. The Gulf Stream is in the same place as it was back in the 1700s, on average. On any one day it is very different, but if you take the average over, say, one year, or even two years, it's in the same place. It's the same map. That is what we call the general circulation of the oceans. It's the part—it's currents, they're moving water, but they're in the same place over hundreds of years. That was the part that I derived from my thesis, from my work—the North Atlantic general circulation. What it tells you is where the currents are taking heat and momentum from one place to the other.

ZIERLER: To go back to that formative piece of advice you received about not to go work for oil companies, was that the general path for students who wanted to pursue industry, going into the oil industry?

ZLOTNICKI: Yeah, because I was in marine geophysics, not in physical oceanography in the beginning. Most geophysicists at MIT ended up in the oil industry.

Arrival at JPL

ZIERLER: You said before you were interested in NASA. Is that how you connected to JPL? Did you recognize the NASA-NPL connection?

ZLOTNICKI: No. When I finished my PhD, I went to Goddard Space Flight Center, which is in Greenbelt, Maryland. I was a postdoc there for two years. While I was there, a couple things happened. My daughter needed hospitalization, and so we spent a fair amount of money, and the salary of a postdoc barely made it, so I had to borrow money from my parents. So I figured I didn't want to be a postdoc for too long. I couldn't be a civil servant because I was not a U.S. citizen at the time, so I couldn't be a civil servant. So it didn't look like Goddard was going to be a good long-term home. The second thing is, my wife, Diana, is from California, and she kept on joking that most of my friends from grad school had gotten jobs in California; how come I didn't? At the same time, JPL was hiring oceanographers because of Seasat, still, and I learned about JPL, and it was in California, and it was NASA, so why not apply? I really liked it, and I came.

ZIERLER: What was your initial position at JPL?

ZLOTNICKI: Researcher. Scientist. But I was hired for a double job, actually. One was as a researcher, 50% time, and one was as project scientist, or science advisor, to a data center. There's a data center at JPL called Physical Oceanography DAAC—for Distributed Active Archive Center. That project has lasted since I came to JPL and it's still alive. It's amazing. I was brought in to make sure that the project would serve the interests of oceanographers.

Planetary Missions and Climate Change Research

ZIERLER: What were some of the big missions you were associated with in your early years at JPL?

ZLOTNICKI: Well, missions happen every decade. They don't happen—there aren't many missions at any one time. Seasat was the first one. Then I was working with this data center for a couple years. And the Navy had launched another satellite called Geosat that also measured sea level. Back in 1987, I believe, the data from Geosat were declassified. So, I went to NASA headquarters and I said, "Look, I don't want to do this data center work anymore. Would you let me just do research alone, with Geosat data?" They said, "Sure, you've paid your dues. You've done it for two years." So I wrote a couple papers using Geosat data, on the Gulf Stream and the Kuroshio, and mesoscale seasonality and so forth. That's how I got started, first with the NODS Data Center and then with Geosat data. JPL at the time was preparing for TOPEX, which would not launch until 1992. In the beginning, the head of the oceans group was a fellow called Frank Carsey who has since retired, and he is a glaciologist. He's not an oceanographer, per se. He does ice sheets. Well, he used to do ice sheets; now he does sculptures. Then Lee Fu became the head of the Oceans Group; we call it group supervisor. When he became the head of the Oceans Group, he saw that the future of oceanography at JPL or at NASA was in assimilating data into numerical models. So, taking the data from the satellites, putting them into a numerical model together with in situ data and ensuring that the result is a consistent picture of the ocean. He began hiring numerical modelers and data simulation experts. So, my first mission was Seasat, second one was Geosat, third one was TOPEX/Poseidon, then this evolution towards assimilation of the data happened. Then came Jason-1, Jason-2, Jason-3, and I have been involved with all of them. Then came GRACE for me, which was a really very happy participation, because I think it's a very powerful measurement technique. Then came GRACE follow-on with which I have not been involved. Finally came SWOT, which I am not involved.

ZIERLER: When you joined JPL, was Seasat already up and running, or you saw that get going?

ZLOTNICKI: No, Seasat had launched in 1978 and died three months later. So we were all working with three months' worth of data.

ZIERLER: What happened? How did it die?

ZLOTNICKI: Well, the joke is—the joke; it's only a joke—is that the CIA turned it off because it was producing very useful data on marine gravity that could be used by our enemies to launch missiles from the sea. The reality is, it had a short circuit, basically. It was a demonstration mission. It wasn't launched with all the care that we do today for missions. As a famous scientist once told me, "NASA, when you build a satellite, one third of the cost goes to build the satellite, and two thirds goes to make sure that it works."

ZIERLER: Was it relaunched essentially the same? Did the circuit get fixed, or was it a different mission afterwards?

ZLOTNICKI: No, it was a different mission. Seasat had like five instruments on it—an altimeter, a scatterometer, a SAR, a radiometer, and a color instrument. The missions that followed it had only one of them each.

ZIERLER: What was your job on the mission? What did you do?

ZLOTNICKI: Used the data. No job on the mission. Used the data. Demonstrate that the data are useful.

ZIERLER: What kind of data did it produce? What was useful to you?

ZLOTNICKI: My expertise was on the radar altimeter, the sea level part of the data.

ZIERLER: What did it tell you? What were some of the key findings?

ZLOTNICKI: In three months, you cannot prove anything. All you can do is show that it's working, show that it recognizes features of the ocean that you know are there, and look a little bit at the sea level variability that it causes, to see where the turbulence is. That was all.

ZIERLER: After those initial three months, what happens next?

ZLOTNICKI: Well, with the data, nothing, because there is no more data, right? Cannot do climate studies with 3 months of data. But that satellite, again—sorry, I'm not going to answer your question entirely—that satellite launched the beginning—because it had five instruments—was the beginning of many other missions. One of them was a SAR, a synthetic aperture radar, which became the basis for everything that Section 334, the Radar Section that's at JPL—and it became the basis for planetary radars. It became the basis for NISAR, which is a current Earth mission. Became the basis for the Shuttle Imaging Radar that Charles Elachi worked on. So, that alone—the SAR. The altimeter became the great grandparent of TOPEX and Jason, and the Jasons, and the European missions, and even SWOT. The radiometer, we have a very active radiometer group at JPL that does radiometers for Earth and planetary. The color instrument did not get used very much more at JPL. It was Goddard who launched the other missions. So, it was the beginning of—it didn't show any new properties of the Earth that we didn't know existed, which was your question, but it demonstrated that each of those instruments would be useful for something specific.

ZIERLER: It was really a technology demonstration, is what you're saying.

ZLOTNICKI: Exactly, it was a technology demonstration. It was not launched for science. There were no scientists at JPL when it was launched. All of the oceanographers at JPL were hired more or less on the year that Seasat was launched. All the first oceanographers at JPL, which were Robert Stewart, Ben Holt, Lee Fu, Dudley Chelton, they were all hired that year, to demonstrate that the satellite was useful for something in oceanography.

ZIERLER: Does this usefulness lead directly to TOPEX?

ZLOTNICKI: Yes.

ZIERLER: Tell me about TOPEX, how that got started, what its principles were.

ZLOTNICKI: TOPEX only had an altimeter. Seasat had five instruments, one of which was an altimeter. TOPEX had only an altimeter and a radiometer to measure the water vapor correction to the altimeter. And it had, not a GPS, but it had positioning sensors, both a radio and a visual laser, to position the satellite. TOPEX became a Cadillac mission, a much more expensive mission. It was not a demonstration mission; it was a science-driven mission. Carl Wunsch, who had been my advisor at MIT, was the father, the science father, for TOPEX. He basically put together a group of scientists who laid out the science that was expected to come out of TOPEX. Of course, TOPEX then went on to measure things that had not been foreseen by the original documents, but that's another story. So, that's what built up the group at JPL. That's what built up the ocean data assimilation work at JPL and so forth. The story is that Charlie Yamarone, who was the project manager for TOPEX from the beginning—and he later became deputy director for science, deputy to Diane Evans—but Charlie Yamarone went to MIT to try to convince Carl Wunsch that this was a mission worth supporting by the science community. He begins explaining to Carl how an altimeter works, and how it measures height and whatnot. Carl apparently told him, "Yes, but can it withstand the rigors of a ship moving, and doing all these things?" Charlie says, "It's not for a ship. It's going on a satellite." [laughs] So, from that misunderstanding of the beginning, a whole mission was born that initiated the long-time series of sea level measurements.

ZIERLER: As you were explaining earlier, at MIT, nobody was connecting sea level rise to climate change. When does that start to happen at JPL?

ZLOTNICKI: The connection of sea level to climate change happened as soon as we began seeing the three-millimeter-per-year rise in sea level in the time series. I would say that happened in the mid 1990s—1995, 1996. I hate to say it, but the guy who wrote the original paper was not at JPL. His name is Steve Nerem at the University of Colorado. He wrote the paper showing how the altimeter was measuring the global sea level rise. It was a purely observational paper. It didn't connect it to global warming or to anything else. But—again, in 1995, 1996—that's what started a race to try to measure how much the ice sheets are melting, how much the ice sheets are melting and adding to the sea level, how much the sea level is growing just because of thermal expansion, just because the water is warmer, and how much the sea level seems to be rising just because the continents are moving a little bit, and they're bending—the water bends the sea floor, and there is a gravitational effect, too. Those three contributors to sea level rise begin to be studied in the mid 1990s.

ZIERLER: How long did TOPEX last?

ZLOTNICKI: I want to say 10 or 12 years. I don't remember now.

ZIERLER: Then the Jason missions flowed directly from TOPEX?

ZLOTNICKI: Yes. And they're all basically the same thing—an altimeter with a radiometer and positioning instruments. From the beginning, there were collaborations with the French space agency, CNES. So, TOPEX was a collaboration. Seasat was a JPL-only mission, in collaboration with Goddard and other U.S. places, but no foreign collaborations. TOPEX from the beginning was a collaboration with CNES. After that, CNES basically took the lead, and the altimeters themselves, which are the key instrument in the satellite, come from France, from CNES, in the Jason series.

ZIERLER: What was different about the Jasons? What made it an advance from TOPEX?

ZLOTNICKI: Cheaper. Smaller. Modern electronics. Solid state electronics. TOPEX was old technology.

ZIERLER: For all of this data that was coming in, given how long TOPEX was, and a continuation with Jason, what were some of the new data telling you?

ZLOTNICKI: Most of the new data went into these massive ocean data assimilation models. They are the same as what NOAA uses to predict weather, or the European Center for Medium-Range Weather Forecasts uses to predict weather. They are numerical models that embody all the equations of motion of the ocean, or of the atmosphere in the other case, and at each time step, if you wish, they take in new data from the altimeter but from all sorts of other in situ instruments, and they make a picture of the ocean, not just the surface bit at all depths, that is consistent with all the data, and with the physics embodied in the equations. That's called data assimilation in numerical modeling. The first thing that it did was allow these data assimilation systems to be well constrained, because the data were global. You didn't have just a few ships measuring here or there; you had global data on height. You had global data on temperature, also. There are other satellites, not from JPL, that measure the temperature of the surface of the ocean. What those systems gave us was a new understanding of the causes of certain processes. For example, why is sea level rising in the Arctic? A colleague from JPL, Ichiro Fukomori, has written some very nice papers explaining what currents are causing sea level to rise in the Arctic, what combinations of currents and heat and waves are responsible for the observed sea level rise in the Arctic, for example.

ZIERLER: Tell me about the Physical Oceanography Distributed Archive. What did the Archive do? What were your responsibilities?

ZLOTNICKI: Back then, it was called NODS, NASA Ocean Data System. It was simply a data center. The idea was that NASA missions have a limited lifetime, right? So during their limited lifetime, they pay for distributing the data, for reprocessing the data, and for all the data part of the satellite, which comes at the tail end of the measurements. These data systems were created with two purposes in mind. One is to continue nurturing the data after the mission died. So, when the mission dies, there is a one-year overlap, closeout basically, for the mission. After that, there is no support. So, what do you do? You just leave the data in some disk or tape, and—? Okay. The idea was that this would nurture the data, and would be able to reprocess the data, as new algorithms became available, so you could squeeze better information from the original data. That's what NODS was created for, and what PO.DAAC, the successor of NODS, was created for. My job was to make sure that the science aspects of the data handling, the data processing, and the relationship with the science users was correct. That lasted a few years.

ZIERLER: An overall question—in the 1990s and the budget cuts after the end of the Cold War—the faster, better, cheaper ethos that was coming from NASA—did that affect oceanography at JPL? Did you feel that budget crunch?

ZLOTNICKI: No, not really. The budget crunch these days comes from the fact that the budget—the overall budgets do go down, of course. It did go down a little bit during faster, better, cheaper. But the research and analysis part was well protected, which is the part that funds scientists at NASA. But the problem now arises from the fact that the budgets are more or less flat, barely keeping up with inflation, but there are a lot more people around. The universities keep on making PhDs, and so everybody applies for the same pot of money. NASA gives some to universities, some to NASA centers, and so the awards have become smaller and smaller. When I came to JPL, I had one account. My time card was one account. By the time I left, my time card had six or seven accounts. And that was me; there are other people who have 10 or 12 accounts in their timecard. That's the main effect that I see with time, the flat budgets with an increasing number of potential awardees.

Charles Elachi and New Directions at JPL

ZIERLER: When Charles Elachi was named director of JPL at the turn of the century, his emphasis on climate change and Earth science, how did that change your day-to-day? What changed at JPL as a result?

ZLOTNICKI: It changed a lot, because finally climate was being recognized as an important topic within JPL and within NASA. We pushed it with NASA also. What changed was the questions we were asking. The missions themselves have these long lifetimes, long gestation times, so none of that changed overnight. What happened also when Charles came was that we created a Center for Climate Sciences within the Earth Science Section, and hired Graeme Stephens to lead it, a very senior scientist, a Fellow of the Royal Society in the U.K. So, the nature of the questions that we were asking changed. But it did not necessarily bring in either more money or different missions in the short term.

ZIERLER: Is this the origins of the Climate Variability program? Does this start under Elachi's leadership?

ZLOTNICKI: No, Climate Variability is what NASA headquarters calls the program that involves—and it's more for historical reasons. The Climate Variability program involves the Ocean Physics program, the Cryospheric Sciences program—because climate is melting ice sheets and glaciers, everywhere—and the Numerical Modeling program. There is a Numerical Modeling for both oceans and climate and weather at NASA that supports GISS—the Goddard Institute for Space Studies—supports the Goddard modeling facility. I don't remember what it's called now. They produce MERRA, a medium-range model for weather, and they support the ocean modeling at JPL. Those three programs are called Climate Variability at NASA, not at JPL. JPL followed the lead and said, "Okay, we are going to call this program Climate Variability at JPL also, because that's what NASA does." Obviously atmospheric chemistry is a real important component of climate variability, but it's not in the program. That's in an Atmospheric Chemistry program, which is separate from the Climate Variability program.

ZIERLER: I'm curious, during the Bush years, if the term "climate variability" is a way of not saying climate change or global warming?

ZLOTNICKI: Oh, no. The Bush years brought this guy who was eventually discredited and fired from NASA, who would—I mean, he was fired from NASA for having lied in his resume. He claimed an undergraduate which he didn't have. [laughs] So he had literally lied in his resume; that's what got him fired. But he was a political appointee. It made everybody very nervous at NASA headquarters. I remember the director for Earth Sciences at NASA would have to review each press release. You know what it is for the director of Earth Sciences at NASA to have to review press releases? But she had to review the press releases, because otherwise they would be censored by this guy, and words like "climate change," "global warming," there were all these prohibited words during that term. He tried to silence Jim Hansen, at the Goddard Institute for Space Studies. He was horrible.

ZIERLER: When did the Jason program eventually end, all of the missions?

ZLOTNICKI: Well, it hasn't. TOPEX was JPL-led, France helps. Jason-1 and Jason-2 were France leads, JPL helps. Jason-3 and the current series, which is called—ach! I have a blank—are led by the meteorological center of Europe, funded through the meteorology, and JPL and France space agencies contribute to that. It's EUMETSAT. I'm sorry; I couldn't remember EUMETSAT. The missions are called Sentinels. Sentinel-6 is the follow-up to Jason-3. It used to be called Sentinel-6/Jason-something. But was renamed Sentinel-6 Michael Freilich. Do you know anything about Michael Freilich?

ZIERLER: No.

ZLOTNICKI: Oh. Very interesting fellow, so I'll tell you more about him in a minute. So, Sentinel-6 Michael Freilich, it was the follow-on, but it was already led by EUMETSAT. So, the series has not died. What has tapered is the NASA contribution to those series, and the leadership contribution. So, NASA contributes, JPL contributes, a radiometer for a correction and a GPS instrument, and that's it. So, they haven't died; they will continue forever. But they will continue with a low level of JPL participation and with a high level of leadership from the Europeans.

Variability and Ice Sheet Melting

ZIERLER: Just a definitions question—what is the cryosphere, or what is cryospheric research?

ZLOTNICKI: Cryospheric research is the study of the ice sheets of Greenland and Antarctica, the glaciers on the mountains—like we have glaciers—and their evolution and their melting. And also the study of sea ice. The continental cryosphere contributes about 40% of sea level rise. So the simple melting and addition to the oceans—sorry, it's actually more like 60%, now that I remember. It's 30% from Greenland and Antarctica, 30% from the glaciers, from land glaciers, and the other 40% from the thermal expansion from the heating of the sea water.

ZIERLER: In following this data over the decades, is it continuously getting smaller? Is there variability from year to year?

ZLOTNICKI: There is always variability from year to year, and there are trends. It's like the stock market. Just think of the stock market. It goes down, it goes up, but if you hold on to it for ten years, 20 years, 30 years, it keeps going up. That's sea level. You have an El Niño and it goes down. You have a La Niña, sorry, and it goes down. The following year, it goes back up. But on average, the—so it goes like this. So it goes up and down, but on average, it goes up. And what goes up is both sea level, the melting of Greenland and Antarctica, and so forth.

ZIERLER: Assuming that carbon emissions continue basically in the same trajectory that they're on, are there doomsday scenarios where we're looking at a situation where there's no more ice in Antarctica or Greenland?

ZLOTNICKI: Well, that's going to take a long time. But there are doomsday scenarios in that you can have catastrophic, meaning very short-term melting of a major part of Antarctica, and breaking of a shelf that brings a whole river of ice into the ocean, and it causes a sea level rise that is very rapid, that would happen over a few years instead of hundreds of years or thousands of years. Sea level rose for the last 7,000 or 6,000 years at less than one millimeter per year. Millimeters per year doesn't sound like much, but if you multiply by a number of years, you can tell that it becomes a large number. Now we are at three and a half millimeters per year, and that's because of what we are doing to the climate. And it's increasing. So, there is a lot of effort to measure the acceleration of sea level. Not just the rise, but the acceleration. Did I answer the question?

ZIERLER: You did. At what point in your career at JPL were you a manager at a level where you had significant administrative responsibilities, oversight of other scientists?

ZLOTNICKI: [laughs] I don't remember the exact year, but somewhere in the mid 2000s, I became a group supervisor, which is the leader of ten people. Then I became deputy section manager, which is heading a group of, at the time, 70 or 80 people, plus postdocs and whatnot, so it is more like 100. The 60 or 70 are all employees, but there are postdocs and there are contractors and so forth, so it's more like 100. Then I became section manager of that section, and then the two Earth Science sections—we had two Earth Science sections, one from the atmosphere down—one from the surface down, and one from the surface up. One dealt only with the atmosphere—atmospheric chemistry, atmospheric circulation, atmospheric composition, and so forth—and the other one dealt with geophysics, geology, oceanography, hydrology, and carbon, on the surface. We combined them—a future director called Mike [laughs] who was at the time division manager for the Science Division, combined them into a single Earth Science section, which has like 150 people plus postdocs and whatnot makes it 200 people. When that combination happened, I stepped down from being section manager and I became assistant manager. So, I have been a manager for maybe 15 years.

The Import and Long Tail of the GRACE Mission

ZIERLER: Before we turn to your work for the Oceans & Ice group, to return to GRACE, the Gravity Recovery and Climate Experiment, how did that get started? What were some of the mission objectives of GRACE?

ZLOTNICKI: I wrote part of the GRACE proposal. I am very proud to say that I wrote part of the GRACE proposal. There was a JPL-er called Jean Dickey who had chaired a National Research Council committee to investigate all the possible applications of gravity—space gravity—in Earth studies. It wasn't about GRACE in particular; it was only to recommend to NASA that a gravity mission be studied. This committee came up with various recommendations, and they looked at what a gravity mission would do for the cryosphere, what it would do for oceans, what it could do for solid Earth science, for volcanoes and plate tectonics and solid Earth science, geophysics. NASA accepted the recommendation, but requested proposals for the mission. There was a proposal from Goddard that involved a gradiometer. A gradiometer is something that is in a satellite and measures small changes in gravity within the satellite. The gravity is a tiny bit stronger down here than it is up here, and it's a tiny bit different than it is here, and in three directions, it measures gravity. The other proposal was from JPL and it was for two satellites that would measure the change in distance between the two satellites. Our proposal won.

ZIERLER: Why do you think? Why was it successful? Why was that a compelling argument?

ZLOTNICKI: For several reasons. Mike Watkins was really the person who put that proposal together. I wrote the oceans section, but Mike was the force behind it. At the time, he wasn't director, of course; he was a regular manager. What made it successful was that we emphasized—the gradiometer had a fundamental problem; it couldn't last long. It had to be super-cooled, and that would last maybe a year or two, after which it would die. The technology of measuring satellite to satellite makes the satellite pair last for 10 years, 15 years, until somebody, something fails, but not because there is a lifetime to the cryospheric system.

ZIERLER: How long did it take to get from proposal to mission, for GRACE?

ZLOTNICKI: I think we proposed in 1998 or 1999, and it was launched in 2002. So it was short. It was actually four years, maybe.

ZIERLER: Were there new technologies that made GRACE particularly exciting or even feasible?

ZLOTNICKI: Yeah. Mike once explained to me that a mission like GRACE had been proposed before to NASA, called GRAVSAT, and it didn't get accepted. Because GPS technology had made it possible to measure simultaneity of time between the two satellites to within a very small fraction of a second. Without that measurement of simultaneity, it couldn't be done. So one technology was GPS proper, and the other technological advance was the microwave link interferometer between the two satellites.

ZIERLER: What were some of the key findings of GRACE? What may have even been a surprise to you?

ZLOTNICKI: The big findings from GRACE in my area were the melting of Greenland and Antarctica. It really did a superb job of measuring the decreasing mass of these huge ice sheets. The melting of glaciers, which it could measure, although the glaciers had to be very large, or large glaciated areas. It couldn't measure individual glaciers. It doesn't have that resolution. For the oceans, it was I would say a bit of a disappointment. We measured acceleration of changes in the Antarctic Circumpolar Current, which I did, and then that generated a few other papers, to follow on, on mine. We measured some deep ocean current. and two colleagues, one from Scripps one from JPL wrote a very nice paper detecting changes in a deep ocean current. But it didn't do very much more for physical oceanography. In solid Earth geophysics, it helped a lot with models of post-glacial rebound, which is—what happens when you melt ice, the mantle pushes—just imagine a viscous fluid mantle, a lithosphere, a little lid on it, and you have the weight, so the weight pushes down the lithosphere. As you remove the weight because you melt ice, it goes up slowly. So it helped measure properties of the lithosphere in the mantle itself. Those were the various changes, the various things, that we found with GRACE.

ZIERLER: In appreciating just the level of ice loss from the sheets in Greenland and Antarctica, how was GRACE different than a simple photograph, where you could just visualize the ice getting smaller? What was more precise, what was more certain, about what GRACE found?

ZLOTNICKI: Instead of a simple photograph, I will tell you about our friends at Goddard. They love lasers. They had an instrument called ICESat, a satellite called ICESat, and then a follow-on called ICESat-2. With lasers, it measures the height of the ice. It's an altimeter Just like the radar altimeter that I used for the oceans, it measures the height of the ice. But instead of being a radar altimeter, it's a laser altimeter. It's very accurate, it's very nice, but it has a problem, while GRACE has another problem. The problem with ICESat is that it measures the surface. It bounces back at the surface. And the surface of the ice is covered with a thin layer—with a layer, not thin—of snow, which is not ice. The ice is much denser. So you don't understand how much of that ice—how much of that thickness is snow firn. It's called f-i-r-n, snow firn. The weakness of the ICESat measurement of volume of ice in Greenland and Antarctica is that you have to assume something about firn. The weakness of GRACE measuring ice in Greenland and Antarctica is that you have to assume something about the mantle underneath, the viscosity of the mantle, or solve for it simultaneously, in order to know—because remember I just told you that as you melt ice, the surface goes back up a little bit, so the height—the mass you measure is a combination of the mass of the ice and the mass of the snow. Of the lithosphere.

To make a long story short, the two measurements, because they have totally different weaknesses, when combined, give you a better estimate. The one you asked about, which was a simple photograph, doesn't give you the 3D version. Even if you could make the photograph be stereo—if you made stereo photography you could get the full topography, but the accuracy is not there. So nobody uses photography alone for ice volume. What we use is it for ice extent. Photography—visual, visible photography—is for ice extent, but laser altimetry or radar altimetry over ice gives you the height, and GRACE gives you the mass.

ZIERLER: I asked earlier at the beginning of our conversation about climate mitigation. As you're explaining to me so elegantly, JPL is a leader in observing the loss of this ice. But is there any opportunity to translate these observations into doing something about ice loss?

ZLOTNICKI: No. What we want to do at JPL, and we have stated it very many times, is not be in the mitigation business—that's for somebody else—but be in the verification business. We will tell you whether whatever technique of mitigation you are applying is having an effect on the system.

ZIERLER: Can you point to an example where the JPL specialty of verification leads to potentials in mitigation, or is that too far afield and we're not there yet?

ZLOTNICKI: I don't think we're there yet.

ZIERLER: What would it take to get there? What might that look like?

ZLOTNICKI: A dangerous major experiment that removes carbon from the atmosphere or shields us from incoming radiation—there are all these wild ideas about mitigation. That has an effect on the rise of sea level, that we can tell you, "Hey, it was going three and a half millimeters per year, and now it goes up by only three." It looks like peanuts, but in terms of the amount of heat that the ocean is absorbing, it's a huge amount. So, we would be able to tell you, by just that small change in sea level rise. Sea level rise is like the temperature of the body; I don't quite know how to explain it better. If your temperature is a few degrees higher, it is an indication that something is not working well in the body overall. Sea level rise is that symptom. The curve of carbon dioxide increase is the cause, and sea level, the curve of sea level rise, is the effect. And we can see the effect.

ZIERLER: What were some of the big projects going on in the Oceans & Ice group when you were group supervisor?

ZLOTNICKI: In the Oceans & Ice group, it was the same—the altimeters, and especially the data assimilation into numerical models. When I was in section management, it became much broader. I became much more aware of missions to measure carbon, missions to improve atmospheric circulation modeling. We have AIRS, for example, an old instrument pioneered by Mous Chahine, who—I have an anecdote about Mous Chahine, though, totally unrelated. We owe JPL oceanography to Mous. He was the one who initiated and fought for it and whatnot. And he became chief scientist of JPL. A very approachable guy. You would go with an idea and he would support it or not. But you would know immediately where you stood. His wife was a professor, a teacher of American history at the high school, the high school that is one block away from JPL, La Cañada High. She was generally acknowledged as the best teacher of American history in the school. She was Lebanese. [laughs] That's the story.

ZIERLER: Wow. [laughs] Victor, when you became deputy section manager, Climate, Oceans, and Solid Earth Science Section, was the Oceans & Ice group within that section, or this was a transfer to some degree for you?

ZLOTNICKI: No, no, it was in that section. It involved oceans. It involved solid Earth, or Earth surface and interior, we call it. It involved hydrology, land hydrology, surface hydrology. We had one atmospheric instrument, the AIRS instrument, in that section also.

ZIERLER: Your portfolio grew pretty significantly with this change?

ZLOTNICKI: Yes.

ZIERLER: What were some of the new areas to appreciate or understand in this new role?

ZLOTNICKI: The environment at NASA kept on changing, at the same time, so we had more small missions that we could propose. For example, one of the missions that we proposed during that time was OMG, which stands for Oceans Melting Greenland, rather than—

ZIERLER: "Oh My God!" [laughs]

ZLOTNICKI: It was an airborne experiment. We hired a guy called Tom Painter during that time, who was a hydrologist. He started the Airborne Snow Observatory that measures the snow cover over California, and therefore how much water you are likely to have in the following season. Then Tom went off and left JPL eventually and became an entrepreneur with his own private company. Those were the areas that we changed. There were smaller missions, airborne missions. I don't remember any major proposals, any major instruments that we managed to initiate at that time.

ZIERLER: Moving closer to the present, going from deputy section manager and then to assistant section manager for Earth Science, did your administrative responsibilities get to a point where it was difficult for you to do science yourself?

ZLOTNICKI: Yes. Some people can do it, and some people cannot, and you just have to know what your strengths are. I am more of a people person, and so I spent a lot of time talking to people and finding out what they need, and how they can be helped and so forth. So, in my case, it took almost all the time, to do the management part.

ZIERLER: That was okay with you, to be somewhat removed from the science, and to serve as a mentor to some degree?

ZLOTNICKI: Yes, it was.

ZIERLER: Tell me about the experience during COVID, when everybody was working remotely. What was that like for you as a manager and just staying connected with your colleagues?

ZLOTNICKI: For me it wasn't very hard, because I already knew all these people, personally, and therefore a Webex, like we are having now, had a different feeling than if I didn't know you at all. Even though you can see facial expressions and so forth, it is different. The conversation is totally different. But I had had the personal conversations with most of these people before, so I knew them. COVID was really hard on the newcomers, all the new people, because they didn't know others personally. They didn't know how to pick up the phone and say, "Hey, want to talk about this for 15 minutes? I have an idea. I want to bounce it off of you." Which I could do because I could pick up the phone, call somebody, say, "Hey, can we do a Webex? That way I can share some slides with you, and talk." They couldn't do that. So that was the worst part, on the younger people, on the beginners, the postdocs, and so forth.

ZIERLER: In the timing of your retirement, was it important for you hopefully to wait out the pandemic to get back to see your colleagues in person before making that decision?

ZLOTNICKI: No, I made that decision based on age, mostly. I turned 71 this year, and I made that decision on age. I did not make it on the basis of COVID or the absence of COVID.

ZIERLER: Tell me about wrapping up your time at JPL. What did that mean administratively? What did that mean scientifically?

ZIERLER: Scientifically, I was winding down almost nothing, because I had wound down that work in the previous few years. Administratively, it was helping my boss find good replacement for me [laughs], find good replacements in my various duties, two or three duties that I had, and transferring all this property that had built up over the years with me, transferring accounts of mine that I had to other people, and finding out who would be a good recipient of those monies, who could manage that money properly. And then, getting rid of a number of books and reprints and things like that in my office that you collect over 30 years of being in the same office.

ZIERLER: Now that we've worked right up to the present, for the last part of our talk I'd like to ask, if I may, a few overall retrospective questions about your career, and then we'll end looking to the future. First, all of your work in oceanography and ocean physics, what have we learned from your research? What do we understand about how the oceans work that wasn't apparent when you began as a graduate student?

ZLOTNICKI: When I began as a graduate student, as I mentioned earlier, the emphasis was still on the general circulation of the oceans, the general circulation being those motions of the oceans which are the same now as they were 100 years ago, more or less. What we have found is how much variability there is in that, and how much of it is possibly—I don't want to get into dangerous territory, separating the human-induced part from the natural variability—but trying to describe at least the natural variability part of it. For example, during El Niño years, during La Niña years, you have more rain, over land, in Australia, for example, which is called an endorheic basin, where the water stays there, and you have less water raining over the oceans. So, sea level literally goes down. It's huge, because the rain has shifted to over land. Understanding those changes, natural changes, natural variability in sea level, natural variability in ice and so forth, that's what has changed and what I have helped contributed a little bit to understanding.

ZIERLER: In all of the debates about climate change, and even climate change denialism, what role has ocean physics played in making the science obvious?

ZLOTNICKI: Well, whether you like it or not—so, we have now things called nuisance flooding. We have a guy at JPL who is an expert on that subject, Ben Hamlington, and we have a colleague at the University of Hawaii who is a close collaborator. Nuisance flooding basically is when many times a year, your town becomes flooded. In the Florida coast, in the Gulf Coast, and so forth, it happens more and more frequently. That's one way to measure sea level rise, not by the millimeters per year that it goes up, but by the invasion of land, how many times a year the sea level is invading land. So, to the denialists, I would point out how many more days a year we are having nuisance flooding, for example, in various cities around the U.S.

Talking to a person who denies—I [laughs]—I had that conversation with one guy, actually at my synagogue. It was hard, because he just focused on what he called the fake data that are out there. At some point, it is very hard to explain the difference between real data and whatever story he has been told about the data. The reason is that we take our information all secondhand. Just think about it. You did not measure COVID incidence or COVID deaths. You believed somebody who told you that 1.2 million people have died in the U.S. You did not measure sea level yourself. You are trusting me, I hope, to believe that sea level is rising, and that the number of nuisance flooding days is increasing. So, we take most of our information from trusted sources. When they diverge, when one set of trusted sources says one thing and the other set of trusted sources says another thing, people believe different things. And until you become a trusted source again, to that person, it is a parallel conversation. It's like parallel universes. You are not talking in the same way. But again, the main problem is, none of us really does these measurements themselves. You believe somebody who is telling you that the vaccine works. If the other TV channel—and you know which one I'm talking about—says that the vaccine does not work, and that's the only TV channel that you listen to, sooner or later you say, "You are lying to me. You say the vaccine works but you are lying to me. I know that Joe died even though he took the vaccine. I heard it on FOX News."

ZIERLER: Victor, you've worked through many presidential administrations since you began at JPL. Do you feel those political crosswinds at your level, from one president to the next? Does that change things at JPL?

ZLOTNICKI: [laughs] So—sorry, I'm going to tell you a story about Argentina first! In Argentina, when the president changes, the department chairs at the university change, at the public universities. So it is as if when the governor of California changes, the chairman of the department at UC Berkeley would change. Which it doesn't, thank God. I had just taken a class called matrix algebra in my undergraduate, and promptly—and then we had a change of government, and a leftist government took power, a leftist president, who put his leftist son in charge of the university—this is a complicated story—and all the department chairs changed, and so forth. That course, matrix algebra, was eliminated from the curriculum the semester after I took it. I went to a professor and asked, "Why is it eliminated?" He said, "Because it's a capitalist subject." "What?" "Yes. It's a capitalist pig subject. Because matrix algebra problems can only be solved with supercomputers. Large computers are not built by Argentina, therefore it is a capitalist subject that we do not want to teach anymore." And he added, "We are thinking of putting a course on the abacus, and using an abacus to calculate things, because we can build those." Of course the abacus story wasn't true, but—so, in Argentina, you feel the changes of administration all the way to the classes that are taught at the public university. Here, fortunately, it's different. I did feel the changes of administration, but they weren't actually that strong in the funding. The joke goes that the Democrats want to fund climate science because they are concerned about climate and they want better science, and the Republicans want to fund climate science to produce more confusion. You know, there is a saying about—I think it's from a famous American writer—"The scientists have shed much darkness on the subject, and if we let them continue, we will soon know nothing about it."

ZIERLER: [laughs]

ZLOTNICKI: Scientists do conflict with each other. We publish results that are trying to demonstrate that the other guy was wrong, and that mine is better than the other guy's. It's human nature. But we base it on data; we don't base it on belief. So, the Republican administrations would fund more climate science in order to increase the level of discussion, and prove that there was no—in that sense, the funding for climate science did not go down dramatically during Republican administrations. What did change was the tenor of the conversation—words that were prohibited, concepts that were prohibited to be released publicly, and so forth.

ZIERLER: Has Caltech been an asset in your career? The historic connections, the management of JPL by Caltech—has that been useful to you at all?

ZLOTNICKI: To me in particular, no. Caltech has not had an ocean physics professor forever. They hired Andy Thompson maybe ten years ago, and he was the first physical oceanographer at Caltech. They also have—well, Andy Ingersoll is an atmospheric—planetary atmospheres person. Jess Adkins is also an oceanographer. But the connection between Caltech and JPL during most of my career was very minimal. Only with the presence of Andy Thompson has it increased a lot.

ZIERLER: Not being a professor, being a scientist at JPL, have you had any mentorship opportunities? Do you get to work with students?

ZLOTNICKI: I did not. A few of my colleagues are lecturers at Caltech. You can be a lecturer, or contribute to a class, and have students, but that is very dependent on the science that you are doing. For example, in oceanography it hasn't happened, but in atmospheric chemistry it is not uncommon. In atmospheric chemistry we have had many more connections.

ZIERLER: For my last question, I would like to ask you to think about all of your accomplishments and where they might head to the future. In all of your work, what are you most proud of? What do you think has had the most significant impact, and where do you see that research going for the next generation in oceanography and ocean physics?

ZLOTNICKI: I feel my best contribution was contributing to GRACE, and therefore the children of GRACE, and on hiring—bringing in some people like Felix Landerer, who is now the project scientist for GRACE follow-on. I got him at JPL despite my division refusing to hire him. It's a long story. So I think my main contribution has been in being a small part of a very nice mission called GRACE, that will, I am sure, continue to make many findings in the future.

ZIERLER: As an addendum to that, what is the long afterlife of GRACE? Where might it lead? What are the discoveries we should look forward to?

ZLOTNICKI: Depending on the configuration of the children of the children of GRACE, on how they are designed, they might be able to tell us about land hydrology, help us predict much better droughts, fire, floods. Depends a bit on the configuration because you have to have—we currently make monthly maps. If you had more satellites, if you configure it differently, you could make daily or weekly maps, which would allow us much better to predict floods, fires, and so forth. One of our colleagues at JPL, JT Reager, has already demonstrated how to do that with a possible GRACE. So, it's not in oceanography. I don't think the changes that it will make in physical oceanography are that important. But it will make many changes in other areas.

ZIERLER: It has been a great pleasure spending this time with you. I want to thank you so much for sharing your perspective over the course of your career.

ZLOTNICKI: Thank you again for asking me.

[END]