Ryan Glaubke

I was looking at your graduate profile and read about how you got into studying climate change. You mentioned experiencing flooding in your hometown. Can you tell me about your experiences, what you witnessed, and why you chose oceanography?

One of the more mundane reasons I chose oceanography is that my father is a fisherman, and I grew up by the beach. With those two factors combined, it was almost inevitable that I would end up in ocean sciences. But more importantly, my interest in climate was motivated by the societal impacts of climate change I witnessed around me.

I grew up close to Norfolk, Virginia and eventually moved there to complete my undergraduate and master's degrees. The climate impacts there are quite pronounced. Several conspiring factors, including climate change-related sea level rise, contribute to some of the highest rates of relative sea level rise in the United States. Norfolk frequently experiences what is known as “sunny-day” flooding or “nuisance” flooding. Even a slightly higher-than-usual tide can flood entire sections of important roadways. To give one example, Norfolk is home to Naval Station Norfolk, the largest naval base in the world and the home to the Atlantic Fleet. Critical roadways that military personnel use to access the base can be rendered impassable by nuisance flooding. This issue has been frequently cited in Congress and elsewhere as an example of how climate change affects military readiness.

Witnessing these events firsthand had an impact on me. Learning about climate change impacts in my undergraduate classes was one thing but seeing it daily in Norfolk made it much more real.

Beyond these headline examples, there are everyday instances that affect everyday people. My grandparents lived in Norfolk, and some of their neighbors would have entire homes flooded through the combination of high tides and storm surge. Whole neighborhoods would be underwater. The situation is quite bad. In some cases, the city is subsidizing the physical raising of houses onto one story tall stilts. It's very weird to see neighborhoods with normal bungalows alongside others that are elevated on 10-foot stilts.

Witnessing these events firsthand had an impact on me. Learning about climate change impacts in my undergraduate classes was one thing but seeing it daily in Norfolk made it much more real. So, that helped motivate me. I realized that if I was going to do any sort of oceanographic research, I should apply it to topics of climate change and try to help clarify the problems and find potential solutions to mitigate these impacts here and elsewhere.

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That's fascinating. What led you to focus on paleo research, studying the past versus the present?

Actually, it was by happenstance. I was in a marine geology-centric program at Old Dominion University (ODU). Honestly, I had no idea what I was going to do with that. I could have mapped the seafloor or something, but none of that had the connection to climate change that I was looking for. Then Dr. Matthew Schmidt, a professor at Texas A&M University, got hired into our program when I was a junior. Since the program was pretty small, I went and introduced myself to him, asking about his research and the classes he would offer. He showed me a figure from a paper he had recently published (Schmidt and Lynch-Stieglitz 2011). He explained that you can take sediment cores from the ocean, analyze the chemistry of the microfossils in the mud, and learn about all kinds of ocean parameters like temperature, salinity, river input, nutrient content, circulation strength, and so on. He showed me a figure of salinity changes over the last 25,000 years in the Florida Straits, near the outlet of the Mississippi River. You could see a huge freshening event approximately 14,000 years ago from when the North American ice sheet was melting. That blew my mind – it was so cool!

So, I took every class he offered during the remaining two years of my degree, read a bunch of his papers, and tried to impress him by taking him to lunch and asking questions about his work. Eventually, I built up the courage to tell him that I really wanted to get into this kind of research. It combined my program’s geology background with oceanography and had the climate relevance I was looking for. I asked if I could be his graduate student, and he said yes! So, I stayed at ODU for another three years to work with him. He was close friends with Elisabeth (Liz) Sikes, and that's how I ended up at Rutgers University working with her and getting the chance to go out to sea. I don't like to think about what would have happened if Matthew had never been hired at ODU. I had no idea what paleoclimate research was until he joined our department, so I'm really glad he did.

Yeah, there's a lot of examples of happenstance in these interviews. People often say, “I had no idea and then I fell in love with this topic.” It makes sense; there are so many avenues to explore.

So, you work with sediments?

Well, technically I work with the foraminifera in the marine sediments.

Can you explain the process of using those as paleo tracers?

Absolutely. Forams are amoeba-like creatures, single-celled, and they live throughout the ocean. They form tiny shells out of calcium carbonate. These shells come in all shapes and sizes – some look like popcorn, some like nautiloids, some like ear lobes. They're about the size of a grain of sand. As I mentioned, they live everywhere in the ocean, and when they die, they settle to the bottom of the seafloor. The soft parts – the single-celled amoeboid part – gets eaten and respired by zooplankton and other organisms, becoming part of the organic carbon cycle. But the calcium carbonate shell survives and gets buried by layers of sediment at the bottom of the ocean.

What’s incredible about these shells is that their geochemistry is a reflection of the water in which the organisms grew... When the shell settles to the bottom and gets buried, the sediment naturally creates an archive, a chronology of ocean change over time.

What’s incredible about these shells is that their geochemistry is a reflection of the water in which the organisms grew. Planktic foraminifera live in the water column and capture upper ocean properties, while benthic foraminifera live in the mud and record deep ocean conditions. As the organism builds its shell, the geochemistry of that shell can tell us all types of things about the ocean – its temperature, salinity, and other characteristics are essentially fingerprinted onto the shell. When the shell settles to the bottom and gets buried, the sediment naturally creates an archive, a chronology of ocean change over time. One quantity I focus on, which I studied for my master’s and am continuing in certain chapters of my dissertation, is the magnesium-to-calcium ratio in these shells, which is indicative of past temperature. The proxy is based on simple thermodynamics. In the crystal lattice of the shell, magnesium ions can sometimes substitute for calcium because they have similar atomic radii. But there’s an energy demand to physically replace a calcium ion with a magnesium ion – it’s an endothermic reaction. When you precipitate calcium carbonate – whether abiotically or biologically like these forams do – you'll get more magnesium in the shell if the water is warmer. There is an exponential relationship that describes this reaction that so many papers, including one of my chapters, have tried to quantify very precisely.

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In effect, this relationship is a paleothermometer. Anywhere in the world, you can take a sediment core, pluck a foram from the mud – whether from modern sediments or glacial-aged sediments – and analyze the magnesium-to-calcium ratio in that shell. Based on this exponential relationship, you can estimate the temperature of the seawater when the foram was alive. This is the closest thing we have to sticking a thermometer in the ocean when Earth’s climate was fundamentally different – like during the Last Ice Age, for example. We can learn how much colder the ocean was during that time, and this kind of analysis is crucial because we know that atmospheric CO₂ concentrations were much lower during the last ice age – about 100 ppm below pre-industrial levels. If we can get a sense of just how much colder the ocean was on average, we can estimate equilibrium climate sensitivity, which tells us how much warmer the planet gets when CO₂ levels double. This is a key factor in projecting how the climate will respond to anthropogenic forcing now and in the future.

There's a lot of other geochemistry that I work on. There are various proxies for environmental variables and ocean parameters that we care about, but the magnesium-to-calcium ratio is the one I probably work on and think about the most. Nevertheless, this general principle applies to all proxies: the chemistry of a foram shell reflects the water environment in which it grew. You can even be picky about the species you study because different species live at different parts of the water column. This allows you to target ocean parameters at various depths. Instead of getting just one state estimate of the ocean at one specific location, you can have a depth dimension as well by pairing multiple species together. It's quite remarkable, actually.

Corals operate on a similar principle, but they typically span a shorter time record. Sediment cores allow you to reach further back in time, but that comes at the cost of resolution. Corals have annual layers, so you can observe seasonal cycles. With sediment cores, a standard 1 cm interval of mud can represent anywhere from tens to hundreds to thousands of years. There's a lot of this balancing between temporal extent with temporal resolution when developing paleoclimate records.

So, that's my little spiel on foraminifera. They're remarkable creatures. It's amazing; these things are everywhere, they're practically ubiquitous in the modern ocean.

It is fascinating what you can do with these microscopic creatures. Do you actually get to work with the sediment cores?

Yes! When I started my master's, there was already freeze-dried sediment waiting for me to work on from a cruise Matthew had been on a decade prior. But in 2018, while I was still working in Virginia, Liz was planning her CROCCA-2S expedition to the Indian Ocean. This was my chance to actually get out there, collect sediment cores, and process them from the very beginning. I got the opportunity to join the expedition and, of course, I ended up at Rutgers working on those samples for my PhD. So, I've seen the whole process from start to finish. From plucking the cores out of the ocean, cutting them into small sections for scanning, splitting them lengthwise, cleaning them, marking the depths, and sampling them at core repositories – I've done it all. And it’s definitely a dirty job.

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I bet it’s rewarding, though.

Yes, very much so. There's a lot of precise and careful consideration, but also a certain intuition, that’s involved when sampling at sea that is best taught in the field. I feel like Liz is a sage. She, for instance, can just look at the sonar readings on the ship and tell us where the best mud is. She'll see tiny squiggles in the sonar and say, “That's where the mud is!”. Next thing you know, we have a core that will provide material for papers for the next several years. It's crazy and a very fun experience.

For your dissertation, you mentioned at least one of the chapters focused on the magnesium/calcium paleothermometer. Was that specific to the Indian Ocean core? And is your entire thesis based on just one core or multiple cores from different regions?

Oh, it's actually so many cores. For the chapter focused on the paleothermometer calibration for the Indian Ocean, I took the very top of about 25 cores we collected during the cruise. The surface sediment in these cores is as close to modern times as we can get, so they can be calibrated against modern ocean conditions to develop a down-core record. Together with 85 other core tops from previously published papers, you get a paleothermometer calibration for the Indian Ocean.

For another chapter, I worked on a single core and conducted a classic down-core temperature and salinity reconstruction, which revealed a really cool story. I won’t dive too deep into all the details here, but essentially, this core came from a region with exceptionally well-mixed waters where a water mass called Subantarctic Mode Water (SAMW) is formed. SAMW is a water mass that ventilates much of the shallow subsurface of the ocean today. It’s formed exclusively in the Southern Ocean around Antarctica, but only in localized hotspots. It plays an important role in transferring heat, salt, carbon, and nutrients from high- to low- latitudes, and it also helps link the deep ocean with the shallow subsurface across the globe that’s crucial for how the ocean overturns.

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With this one core, I was able to ask: how have the physical properties of that water mass changed over time? That led to a lot of discussion about what waters contribute to SAMW formation, and what implications those source waters have for the heat, salt, and carbon budgets of the Indian sector. All of this insight came from just one sediment core!

For my final chapter, I explored when and where the deep ocean released carbon dioxide at the end of the Last Ice Age. During the Last Ice Age, the deep ocean stored a significant amount of CO₂, locking it away from the atmosphere. The reduced greenhouse effect contributed to the colder climate. But once deglaciation began, that CO₂ was “exhaled” by the ocean back into the atmosphere, increasing the greenhouse effect and helping drive the planet out of the last ice age.

There's some debate about this, but it’s generally accepted that much of this CO₂ was released from the Southern Ocean around Antarctica, where about two-thirds of the deep ocean comes in contact with the atmosphere today. But there are still open questions, like did the Atlantic, Indian, and Pacific sectors of the Southern Ocean outgas this CO₂ all at once, or did they have different timings and paces of release. To tackle that, I compiled high-resolution records of CO₂ release based on the shell chemistry of benthic foraminifera, including samples generated from our own cruise, and compared them across the Southern Ocean.

So, it's actually 25 multicores and four gravity cores that I ended up working with for this thesis. And that’s not even counting the seawater samples I haven’t mentioned, which just got published! You can probably see my hair falling out through the Zoom call, but it all comes together into this really cool story.

That sounds like a lot of data analysis.

Oh, so much! You're giving me a break from it right now, and I couldn't thank you more!

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You've already mentioned the final chapter of your dissertation. Does that mean you're almost done? Where are you in your PhD process? Hopefully, that's not too stressful of a question.

It's getting closer every day. This is the end of my 5-year stint. Thankfully, the pandemic didn’t severely disrupt my work when I first started, so I’m still on track. I've been sitting on this data for a while, thinking about it. It’s always easy when it’s just a bunch of figures and you can handwave and say, “Oh, how cool is this!” But when it comes time to formalize it and put it into writing, that’s when it really gets tough. So yes, very soon, I should be finished!

Congratulations! That’s such a huge milestone. Have you already thought about what comes next?

Thank you! Well, soon I’ll be starting a postdoc position in the Geosciences Department at the University of Arizona working with Kaustubh Thirumalai. We’ve done some work together in the past, but now we’re bringing some of our prior methods and techniques to bear on a different climate period: the Pliocene. This is a relatively warm period of Earth’s history about 3 million years ago, and the last time atmospheric CO₂ was as high as it is today. So, we’ll be taking a look at a potential analogue state to our future and seeing what it can teach us about future climate change.

Wherever I end up, I’d love to continue going out to sea, doing research, and working with the incredible teams I’ve been a part of. But I really want to be in a place that values both research and teaching.

But beyond that, I’ll be looking for my own position somewhere. I’d love to open a lab and start my own research program so I can continue contributing to our knowledge of Earth’s climate. But importantly, one of the main reasons I got into all of this – besides enjoying the subject, learning something new every day, creating new knowledge, and nerding out over cool stuff – is that I love teaching. I've known that ever since I taught guitar lessons as a teenager.

When I was doing my master’s at ODU, I got the chance to teach an introductory Earth Science course. I even wrote, developed, and proposed my own course at Rutgers, but unfortunately, the pandemic and its financial impact put that on the chopping block. Still, I really enjoy teaching freshman and sophomore students – many of them are first exposed to ocean and climate science in that setting. It’s great to show them that scientists aren’t just lab coats in an ivory tower or experts on the news, but normal, everyday people working to solve one of the planet’s hardest problems. And I love bringing that "wow" factor to our science, just like Matthew did for me when I first walked into his office.

Wherever I end up, I’d love to continue going out to sea, doing research, and working with the incredible teams I’ve been a part of. But I really want to be in a place that values both research and teaching. I also enjoy public engagement, so any chance to talk to people about what I do is a bonus. I’m not sure if any one university or institution fits that balance perfectly, but we’ll see!

It sounds like research-focused positions are the norm. But there are definitely institutions that have a much better balance.

Have you had any interest in studying the Antarctic in any way?

I’ve thought about it a bit, especially since, at heart, I’m an oceanographer. If I were to get as close to Antarctic research as I can, I'd have to focus on oceanography. One interesting question is about Antarctic Bottom Water, which forms along the Antarctic coast, mostly in polynyas. These are areas where wind pushes sea ice away, exposing more surface water and forming more sea ice. The process excludes salt, making the water incredibly dense. It turns into this dense brine that spills over the continental margin and spreads out along the bottom of the global ocean.

There was a recent paper by Aviv Solodoch and his collaborators that showed Antarctic Bottom Water isn't just one uniform water mass. It forms in multiple different locales around the Antarctic coast: the Weddell Sea, the Ross Sea, Prydz Bay, and the Adélie Coast. Depending on where it forms, it contributes differently to the bottom water in various ocean basins. For instance, the Weddell Sea, located in the Atlantic sector of the Southern Ocean, fills the Atlantic more than the Indian and Pacific Oceans. Meanwhile, the Adélie in the Indian sector contributes more to the Indian Ocean, and so on.

The question of whether these different "flavors" of bottom water have a significant impact on how the deep ocean responds to climate change is still up in the air. That would be a great project to work on!

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That sounds like an interesting proposal! I know it’s a tough time for Antarctic fieldwork proposals, but hopefully, things will improve in the future.

I would love to see Antarctica; I know that much. My roommate is a biological oceanographer in the program at Rutgers, and he works with the Palmer Station LTER (Long Term Ecological Research). He spends three or four months a year there, almost every year, and I’m so jealous! He complains sometimes because it’s a long stretch of time but come on—he gets to hike on glaciers!

As we wrap up, what advice would you give to early-career scientists interested in oceanography or climate research?

If you really want to get into ocean and climate science for the same reasons I did – a desire to understand these overwhelming challenges, contribute to solutions, and indulge your curiosity – there's never a dissatisfying day in the office.

My practical advice would be to take advantage of the fact that most STEM programs waive tuition and pay you a stipend for postgraduate degrees. If I had to pay for my master’s and PhD, I probably wouldn’t be here. Having that kind of benefits package opens up so many doors. I don’t come from a wealthy background, so that really lowered the barrier of entry for me – not to mention what it does for people from traditionally excluded groups. So, that’s my advice: if it’s going to be paid for, why not do it? And if you end up not liking it, you still walk away with a master’s degree and probably a better-paying job down the road!

If you really want to get into ocean and climate science for the same reasons I did – a desire to understand these overwhelming challenges, contribute to solutions, and indulge your curiosity – there's never a dissatisfying day in the office. I’d say, jump in, the water’s fine! Well, it’s probably too warm – that’s the problem! But seriously, if you're willing to learn, work hard, stay persistent, and develop a solid support group, you’ll do great in grad school. At the risk of sounding a little preachy, this is such an important topic for our collective future. The more smart, engaging, and personable people we have in this field, the better. And whatever we can do to lower barriers to entry should happen. So, my advice is: go for it!

Thank you for your time and good luck with finishing your dissertation – you’re so close!