Melisa Diaz

Your work involves studying the geochemistry of ice-free and ice-covered environments in both Greenland and Antarctica, but on your website, it says you also study environments on other planets too. How did you become interested in this field of study and what excites you about your work?

I believe that science and finding your place in science is a little bit serendipitous. Early in high school, I was convinced that I was going to be an environmental lawyer. I took an AP environmental science class in the first year the program was created and we watched a movie called A Civil Action starring John Travolta. The movie was about some companies that were polluting a local town’s water, and John Travolta’s character was a lawyer hired to represent the residents in a lawsuit. I thought, this is so cool! I’d always wanted to be a lawyer and I thought that this was going to be my field. Well, we watched the movie and it was so heartbreaking to know that these lawsuits take place over the course of years. It’s not like you see on super fictionalized TV shows where it happens over the course of a month. It's a process that takes years, and there’s just a settlement at the end. This was over a decade ago, but I remember a sad scene at the end of the movie where Travolta’s character is standing by the river, looking at an industrial plant that is still polluting the water. That was when I decided that I never wanted to go into environmental law. Those lawsuits take so long, and it's pretty much whoever has the most money that ends up in the best situation in the end.

I can imagine it would be hard to decide to go down the lawyer path after watching that movie.

Yes, but I still really liked science. In undergrad, I started off at the University of Rochester thinking that I was going to study nanotechnology and work with small robots that were going to help clean up oil spills. Then I got introduced to polar research and thought that's pretty cool, so I started working as an undergraduate at an ice core lab. I was pretty lucky that my academic advisor was an ice core scientist. He needed a lab manager and a technician, and I had some research experience prior to joining that group. I went with them to Greenland for a field season at the end of my senior year. I just remember landing at Summit Station and stepping off of the Herc (short for Hercules C-130 aircraft) and being stunned at how beautiful it was. And that’s kind of how it all happened by circumstance. I instantly fell in love with polar research. It was one of those moments where you see something and you just think this is definitely what I want to do.

At what point did you decide that geochemistry was the way to go?

It must have started in high school. I took a bunch of science classes and thought that I would be an atmospheric scientist in college. I guess I still consider myself one, though I say that with an asterisk because my applications are a bit more interdisciplinary. I took biology, physics, and chemistry classes in high school. I’m very fortunate that we have all those different science courses in the public education system in Massachusetts; I know that's special and I acknowledge my privilege. I realized that I just wasn't as excited about biology. I thought it was cool and interesting, but I loved how in my chemistry class, my high school teacher had us go out into the environment; we would collect lake samples and do some of our chemistry labs with those, which was really fun. That's how I got into the environmental sciences. Then later on as an undergrad, I took an atmospheric chemistry class and I was obsessed with it. But I realized that I didn't really want to do modeling; I wanted to be out there in the world, collecting samples and doing more lab work.

You mentioned before that your first polar field experience was in Greenland which must have been quite special, but most of your PhD work was in Antarctica. Could you compare your experiences and what your first time in Antarctica was like?

"At first, it looked like what I remembered Greenland to look like. But after we landed, the ice field and the landscape was just so dynamic."

My first season in Antarctica, I was actually supposed to go down with Berry, but unfortunately he couldn't make it. At this point, I hadn’t been on an international flight before. I’d been to Greenland but that doesn't count because the flight is through the Air National Guard. So this was my first real international plane ride, and I was flying by myself to New Zealand, which was such a crazy experience. I think what shocked me most was how long it takes to get to Antarctica. Of course, we were “stuck” in New Zealand for a week or so before getting on the C-130 to fly to McMurdo. I have all these pictures of me poking my head in the small window at the back of the plane. At first, it looked like what I remembered Greenland to look like. But after we landed, the ice field and the landscape was just so dynamic. The time I spent in Greenland was at Summit Station which is very flat, but had interesting weather and cool optical effects in the atmosphere. And it was beautiful in its own way. But showing up in Antarctica was incredible, getting on Ivan the Terrabus and bouncing our way back to McMurdo Station. They shuttle you directly to the Chalet to brief you, and I said “Wait, can you give us a minute?”. Looking at the Royal Society Mountains and realizing I’m literally standing on part of an active volcano, I just needed a moment to take that all in. So for me, arriving in McMurdo was very different from Greenland; it kind of felt like summer camp for adults with all of the dorms and everything. What I really appreciated about being there was the people; they’re some of the smartest, most capable, and most talented all around. For example, the dishwasher may have a master’s in biochemistry, but they’re so taken by Antarctica that they come back every year to wash dishes and talk with scientists. To interact with the mechanics, the helicopter pilots, the power plant operators, everyone is just so smart and skilled. The community in Antarctica is what made me absolutely fall in love with it, so that was the biggest difference for me coming from Greenland to Antarctica.

Image

There are definitely some good people down there. It sounds like you may have been there awhile. How long was your first field season and what were you doing?

"What I really appreciated about being there was the people; they’re some of the smartest, most capable, and most talented all around."

For my first season, I arrived in December and left in February. I was primarily a beaker-townie hybrid supporting the Dry Valleys Long Term Ecological Research (LTER) project (see Berry’s interview for more details). I spent most of my time working in the Crary Science and Engineering Center Building managing the total organic carbon and total nitrogen instruments. Folks would come back from Dry Valleys, bring me samples, and I would run them. It was funny because I was driving the “Stream Team'' crazy because I’m obsessed with Phantom of the Opera. I played the whole soundtrack every single day, because when I was making my standard solutions to help calibrate the instruments, I used the music to help me keep track of time and my schedule. I remember in the beginning, some of the members of the Stream Team were working on the other side of the lab. And they would say, “Melisa, can we please change the music?” and I said “No! You have to appreciate how wonderful this is''. And then after a few days they admitted it was pretty great and they would sing along. I guess I forced them into appreciating the Phantom of the Opera. While most of my first season was in the lab in McMurdo, I did get to go out on some day trips and I stayed overnight at the field camps in the Dry Valleys a couple times. I actually got quite an overview of Taylor Valley. I was able to help collect samples near West Lake Bonney, Lake Hoare, Lake Fryxell, and New Harbor over various day trips.

Tell me a bit about the fieldwork involved for your recent work near Shackleton Glacier. What season was this and how long were you in the field?

This was my second Antarctic season and it was another serendipitous moment; I actually wasn’t supposed to go to Antarctica that year, and that project became the major component of my dissertation. Another person on our team was supposed to go but a few weeks before deployment plans changed. I was really excited to get to go and I think being at Shackleton and interacting with the rest of the team was so influential for my career, and really has shaped the type of scientist that I am today.

Shackleton was a pretty quick trip; I think we were only there for maybe two and a half weeks or so. Every day we would get up, go on the helicopter, and fly to a new location. I’d say it was such a great field season because not only did we sample every place that we needed to sample, but we even got to get to some sample sites on our bonus list.

The weather must have been great then?

"And that is just so incredible to think about: that out of 7 billion people on this planet we were the first ones there."

This is super subjective, but Shackleton is the most beautiful place in the world. The sun was always shining and if it wasn't, there was this really cool fog that would roll down the glacier. It was freezing fog, so I have some cool pictures of my hair frozen with ice in it; it was just the most beautiful place. It wasn't always great weather but that's one of the things I loved about it; each different ice-free area that we went to was so unique and special that it was just an exciting sampling trip. And some of the places, we are the only people that have ever walked there. And that to me is just crazy to think about: that out of 7 billion people on this planet we were the first ones there.

Image

I can’t imagine how incredible that must have felt. So what exactly were you studying at the Shackleton Glacier and why is it an important area to study?

The goal of our project was to understand how ecosystems respond to the advance and retreat of glaciers. We needed to pick a place along the Transantarctic Mountains that was an interesting site for several types of scientists. At Shackleton camp there were actually a lot of different science teams. There were the glaciologists, the geologists, the vertebrate paleontologists, and then our ecology team. What's great for us is that it's an area that's not currently actively influenced by sea spray; it also has a really interesting and complicated glacial history. We know that some of the peaks that are currently exposed were covered by glaciers in the past, so now we can start to use that as a variable. How does glacial history affect salt cycling, ecosystems, etc.? The Shackleton Glacier region is remote, so we don’t have to worry about the influence of humans or human disturbance either. Actually, there’s a really interesting paper (Pertierra et al. 2017) where the authors looked at the human footprint score in Antarctica. The Dry Valleys have a high footprint score, since there are quite a few people that go there, but most of the areas along the Transantarctic Mountains have a low score.

Shackleton also has a lot of ice-free areas on either side of the glacier. That means that we can test the effects of not only elevation – because we have sites at similar elevations – but we also have sites at similar latitudes and with similar surface exposure ages. It's so rare that in a place like Antarctica you can have a natural replicate; it makes testing our hypotheses really interesting and can help identify some of the variables that are influencing the biology.

Could you explain to someone who’s not a geochemist what variables you are studying in the soil, and how these variables help you map out biodiversity?

We collected surface soils from 12 locations along the Shackleton Glacier in transects perpendicular to the glacier. One of the reasons behind that was to maximize the variability in our samples, but also, because the glacier has advanced in the past, those transects hopefully encompass soils of different exposure ages. For one aspect of my project, we looked at atmospherically derived beryllium-10, which is a cosmogenic nuclide that radioactively decays once it falls to the surface and is generally immobile. So by looking at the concentrations of beryllium-10 in the soil, how it's maybe infiltrated the soil column, we can potentially use that as a proxy for glacial history. Once the glacier recedes over a patch of soil, that starts the clock in terms of surface exposure because that’s when berryllium-10 can start accumulating. So getting soil age estimates from the beryllium-10 data is really important for our biologist colleagues looking at ecosystem structure in relation to glacial history. That was one of the aspects of the project that I was leading.

Image

Image

I was also interested in the salt and nutrient composition of the soil -- thinking about how we can use those data to understand landscape development and understand the wetting history of the region. Questions like: “How recently in the past has there been liquid water?” or, “Is there an active hydrological cycle in these areas?” This ties back to our biology colleagues, because most life on Earth needs water to survive. My data show that these are super salty soils and water helps to wash away some of the salts. From the soil leaching experiments I did, we found some soil leaches to be 10 to 100 times saltier than seawater. Coming back to the biology component, if you have super salty soils, generally your biodiversity is lower. We then looked at how nutrients vary across the region, the sources of the nutrients and how that relates to where organisms are living (biogeography). It’s such an interesting region from a geochemical perspective.

As someone from a different field, I found the idea of biogeography fascinating. Based on your field observations, you were able to utilize machine learning as a tool for predicting and interpolating geochemical trends across your field region. Can you tell me a bit about how the model works?

While I wasn't specifically looking at biology – that’s work some of my collaborators are focusing on – it is well known that nutrients and salts play an important role in where we find life, where we don't, what types of life we find, and how diverse those organisms are. If you look at the distribution of salts and nutrients across a region, it seems to be really tied to geography. This makes sense when you take a second to think about it; the sites that have been exposed for a long period of time in Antarctica are at high elevations and are far inland. Those areas have a lot of salt, because we know that the salts are coming primarily from the atmosphere. On the other hand, the sites that have been recently exposed by glacier retreat might have a different nutrient composition, such as more phosphorus due to glacier-driven chemical and mechanical weathering of rocks. So taking these variables (distance from glacier, elevation, latitude, etc.) and plugging them into a Random Forest model to predict salt concentrations, I honestly was surprised that it worked as well as it did. The model did a really good job in the Shackleton region of predicting salt concentrations; in another region of the Transantarctic Mountains, it did a decent job of predicting gradients. While the concentrations weren't necessarily exact for this other location, the model can adequately predict trends. For example, as we move up in elevation or as we move away from the glacier, how do the salt concentrations change? The model I developed is fairly simple and all of the code is freely available (Diaz et al., 2021) for anyone who wants to look at it. I purposely published all my work in open access journals so that we can keep adding to this soil geochemistry database. Hopefully with more data points, we can better understand habitat suitability across the Transantarctic Mountains. Maybe then we can start expanding this work to some other Antarctic analog environments, like Mars.

What predictions were you able to make about the past biodiversity of the region or projecting into the future?

That’s still up in the air. I think all of the geochemistry work that we had originally set out to do is done, but these samples are so interesting. It’s pretty funny; it's a combination of bad luck and complicated sample matrices, but I ran the samples and the instruments broke on probably six different occasions. Oftentimes we'd run a sample and the nitrate concentrations were so high that it would clog up the instrument’s plumbing. So, I hope to get back to you on that question, but the work so far relating the geochemistry to the biology has been really fun. We currently have a paper in JGR Biogeosciences, where we found some soils that had no detectable signs of life using modern methods. And that’s due in large part to the interesting and complicated soil geochemistry. It’s such an interesting finding, because if you were to take a gram of soil from your backyard, you would find a billion nucleic acid molecules. But the fact that we can take a gram of soil from some of these places at Shackleton and find nothing using the same methods is mind-boggling. We're not saying that the soils are sterile, but we tried our hardest to find any signs of life and we couldn’t.

So that work was the focus of your PhD, but you are now a postdoctoral scholar at Woods Hole Oceanographic Institution. When did you make the move and who are you working with?

I started my postdoc here September 1, 2020. Honestly, it’s been a little tricky trying to start new research in the middle of a pandemic. I haven't been able to get into the labs until the past month or so. I’m super grateful to everyone for being so supportive and helpful in getting me to this postdoc. I was drawn to WHOI because of the people; I really wanted to do something different than my PhD and do research on ice. I work with a few folks here: Sarah Das who's a glaciologist who works primarily in Greenland, though she's also worked in Antarctica to understand mass balances of glaciers; Chris German, who is a hydrothermal vents person, and he also works on the Network for Ocean Worlds (NOW) trying to understand habitability on icy satellites, such as Enceladus and Europa; and Catherine Walker, who is another glaciologist, but more on the modeling side. She works a lot with remote sensing data and satellites, such as IceSAT2. So this group is quite different from the geochemists, like Berry Lyons, or the ecologists that I’ve worked with in the past. I’d like to take the skill set that I developed during my PhD and apply it to a new system with new questions.

What sort of projects have you been focused on so far?

My work with Sarah Das involves understanding the distribution of nutrients on Helheim Glacier, which is a major outlet glacier of the Greenland Ice Sheet. This is a project that Sarah has funded with the Heising-Simons Foundation. We’ll be heading up to Helheim Glacier and collecting ice cores that I’ll use to look at trace metals. We’re working with a pretty big team that’s trying to understand the surface mass balance of Helheim. This was another serendipitous opportunity where Sarah said, “Hey, I actually have two field seasons going at the same time, and I need somebody to go on this Helheim project, do you want to go and use some of the ice to do your own analysis?”. It worked out really well.

With Catherine Walker, I have a side project that stemmed from my PhD work. At Shackleton we found these ponds from looking at historic flyover images. We know these ponds have changed a little bit over time, suggesting that there is an active hydrological cycle in some of the areas that are now ice free. This is really interesting because these ponds are at 86°S, and yet we know there’s a significant amount of glacial melt from the water chemistry. I’m currently writing a paper on this work which will hopefully lead to a future proposal with Catherine as the satellite remote sensing expert. She and I have a summer student here through the Woods Hole Partnership Education Program (PEP) who is going to help us quantify other lakes in the Transantarctic Mountains with the goal of understanding hydrological changes in far South regions.

Another one of my projects is with Chris German and Keven Hand, who is at the NASA Jet Propulsion Lab, analyzing sea ice cores and trying to understand nutrient distributions with a nod towards the work of the Network for Ocean Worlds (NOW). The community is almost positive that Enceladus and Europa have ice shells with oceans beneath, similar to what we have in our ice shelf and sea ice systems on Earth. I’m interested in understanding the role of that outer icy layer in collecting nutrients or collecting bio-signatures.

Am I going to complete all of this, during my postdoc? [Laughs] Probably not.

Those sound like really cool projects, some stemming from your doctoral work and others off in a completely different direction. Bringing it back to that idea of serendipity, it's great that you’re open to exploring new fields and it's good for students to know that they have the ability to go in a new direction during their postdoc.

Absolutely. One of the things that is super fun about working at the poles is that it’s common to relate environments in Antarctica to environments on Mars and to environments on Europa, Enceladus, and other satellites. I think scientists are hesitant to make those direct connections and for obvious reasons; while these systems have many similarities, they also have a lot of differences. But that's always something that's been interesting to me – to shift gears a little bit and try out this ocean worlds research that is complementary to the research I’ve already done in Antarctica.

So, working at WHOI on these projects, are you diving into the oceanography side of things at all?

WHOI is an oceanographic institution. It's great to be a postdoc here; because while there are a lot of folks you would normally classify under the traditional oceanography umbrella, there are others whose work has shifted a little bit more towards a climate-ocean focus over the past few years. And those projects are centered on understanding how different systems interact. For our Helheim work, we’re up in the accumulation zone and not actually near the ocean. But some of the chemicals that I’m looking at in the ice are sea aerosols or metals that have been transported over oceans. Other Helheim teams are at the glacier-ocean interface. The Ocean Worlds work is a bit more on the oceanography side since I’m looking at sea ice. It’s really fun to be at a place where I am thinking about the work that I do through a different lens.

I think it's great that you’re bringing your different lens to that group. I think science in general is becoming more and more interdisciplinary and I think that's definitely for the better.

I believe that the students play a major role in driving that. Maybe I can use myself as an example. I was a geochemistry PhD student looking at stable isotopes and concentrations of salts in the soils at Shackleton Glacier. I collaborated with ecologists to apply my geochemistry work to help understand ecosystem structure following glacier retreat. It was a unique and informative blend of expertise. The students are the ones that are sitting in that in-between spot, where on their committees, they might have their advisor who may be a glaciologist but they might also have somebody else who's a physicist or a chemist or a biologist. They are the bridges connecting scientists across disciplines. Students make interdisciplinary science; they’re not just fitting into it, but literally being the ones creating it.

Absolutely. Speaking of students, I see from your resume that you’re passionate about outreach, can you tell me more about the outreach work you have been a part of?

"I want to take science that we do in isolation in our labs and in the field and bring that into the real world; bringing in the citizens who are actually paying for research and are affected by it is really important."

I was very involved with the outreach group at the Byrd Polar and Climate Research Center as well as the Society for the Advancement of Chicanos/Hispanics, and Native Americans in Science(SACNAS). I want to take science that we do in isolation in our labs and in the field and bring that into the real world; bringing in the citizens who are actually paying for research and are affected by it is really important. While I primarily study Antarctica and now some Arctic systems, I also do urban geochemistry research as a way to start getting people interested and involved in science. I believe that as people who live on this planet, we all deserve a fundamental understanding of the cycles that make our planet habitable. Places like Greenland and Antarctica play such a crucial role in our climate and ocean systems, and that information isn't always disseminated to the general public. So that’s something that I really am inspired to do. And I also care about doing outreach as a way to increase the representation of people of color and women in Antarctic science and engage with the public. In terms of public engagement, I actually hear a lot of folks respond to climate change science with, “Well, there are other planets in our solar system that we can go to. We can go to Mars.” It's a great opportunity to start showing people some pictures of Antarctica and talk about how crazy this environment is and say “Look at this ice-free, barren, salty, dry area at Shackleton Glacier. This is still 10,000 times more habitable than the environments we see right now on the surface of Mars.” Nobody lives on Antarctica, it's harsh. We only have these microscopic organisms that can sometimes survive. So, when people say that Mars is our backup plan I try to help them realize that it is not a place that anyone would want to live, whereas the planet we live on is super special and worth protecting.

Image

You’re right, I hear people talk about Mars as a plan B all the time, but I never considered that as a teaching opportunity. One final question that brings things full circle. Thinking back to how you got into the field, what advice would you give to early career scientists who are trying to get involved in Antarctic research?

I honestly never saw myself being a polar geochemist. Again, I thought that I was going to be working on oil spills and nanotechnology. This is actually something that I communicate with students when I do outreach. I feel like there's a lot of pressure on us to have our paths defined and carved out at a young age. Even though I’m very Type A – I’m definitely a planner – I realized that things just work out in the end. I’d probably be happy doing that nanotechnology work. I could probably be happy doing a bunch of other different things, but this is the path that was right for me at the right time and I'm really happy where I ended up. I feel like if you have already defined a single path for yourself, it's going to be difficult and you're going to have to make a lot of sacrifices to keep on that path. That’s totally fine, but if you just look around a little bit while on your journey, you'll see that there's actually some super cool work that’s related or tangential to your research that you maybe hadn't considered before.

"As long as you are focused on what seems right to you at the moment and what seems interesting and exciting to you, you’ll end up doing something that you really love."

Back to that recurring theme of serendipity. My advice would be to be open, not just open to the opportunities that are available to you right now, but also to opportunities you are not aware of yet. Know that just because you go in a slightly different direction doesn't mean that those doors of opportunity close. Right now, I'm coming from a soil background back into the ice world, and that is a completely different perspective that I didn't have before when I was an undergrad; I think it makes me a better scientist because I now approach this research from a unique, systems focused lens. It’s important to realize there's not just one path, and these paths branch and converge and cross. As long as you are focused on what seems right to you at the moment and what seems interesting and exciting to you, you’ll end up doing something that you really love.