Climate Change: Past and Future

In an interview this week, Owens talked about how his $75,000 award will advance his research; what ancient isotopic ? x Isotopic are different forms of the same chemical element that have slightly different atomic weights due to varying numbers of neutrons in the atom's nucleus. signatures can tell us about the Earth's history and modern climate change; and how nearly failing out of college became the turning point that launched his career.

When did you find out about the Sloan Research Fellowship?

It actually was on January 27, which is my birthday. It was a really nice birthday gift. They sent a nice email, which was quite a shock as it came through. You end up reading it at least three or four times thinking, "I clearly have misread this." It comes with some funding for future research, so we can go after new questions.

What kind of research do you do?

I'm a metal isotope oceanographer and paleo oceanographer. I'm interested in how certain tools — specific isotopes — can tell us about past Earth and climate change, and in how we can bring these tools together to learn new information to provide a more in-depth, nuanced understanding of how climate has changed in Earth's history. We're interested in the timing of these changes — when they happen, especially compared to extinctions or explosion of new species. But also, how severe are these climate change events? Did the ocean not only experience a loss of oxygen, but also become incredibly toxic because it contained hydrogen sulfide that caused these extinctions?

To understand these nuances, you have to look at a variety of isotope tools, which we largely haven't done in our field because they are each difficult measurements. But we're getting to a point where we can do this.

What does your research process look like?

The amount of work from start to finish is broad. We have to go out in the field and collect the sample first. Depending on the time period and what type of rocks we're analyzing, that will take us all over the world. If it's relatively recent geologic history — the last 200 million years — we have ships that go out and drill the ocean floor and get sediments and rocks. If it's older, then we go collect rocks that are generally uplifted onto continents.

From there, we bring this back to the lab and cut the rocks. Then we'll powder it so it becomes a nice, smooth, homogenized powder. We take it into the lab and become more like lab rats — the geochemistry part. We dissolve the rock almost entirely, or we might extract out certain portions, filtering out different elements or minerals. Then comes the important part: purifying the sample for the specific element that we're interested in. We then take that and run it on one of the mass spectrometers at the MagLab to analyze the isotopes of those various elements. At bare minimum, if everything is working perfectly, it's about a year from start to finish, from collecting the samples to actually running them — but usually longer.

Can you give a specific example of something you've discovered?

The isotopes we're interested in are what we call "proxies," which tell us information about the environment that occurred at a certain period. These elements aren't direct recorders, per se, of oxygen in the oceans. But they have a chemical fingerprint that allows us to interpret changes in oxygen in the ocean.

For instance, a lot of the work I've done in the last five years at the MagLab has been on thallium and vanadium isotopes. The reason thallium is so powerful is that it responds to changes in manganese oxide burial — the burial of these precipitants out of the ocean. That's important because manganese is the first element that responds to changes in oxygen. So, if oxygen is present, manganese will bond to it and form these manganese oxides, which take thallium out of the ocean and have a different isotopic signature. And if there's no oxygen, that manganese oxide that was once buried will actually re-dissolve, and manganese will go back to the ocean and not affect the thallium isotope signature. Thallium allows us to fingerprint changes in manganese, which is indirectly (but our best record) related to the amount of oxygen in the ocean. That's how thallium works as a "proxy." And what we've found out here in these last few years, which has been groundbreaking, is that the thallium is changing earlier than any other isotope proxies in the geologic record. And much of this response coincides with the start of extinction events, which we previously could not fingerprint. We just knew that the extinctions happened, but didn't have a good record of ocean oxygenation.

What makes you excited about that discovery?

It's exciting to understand Earth's history. But, to be honest, it actually scares me a little bit, because this discovery suggests that the loss of oxygen in the oceans directly has an impact on extinction events. Currently we're losing a significant amount of oxygen in our oceans. In the last 50 years, there has been a lot of data that suggests that this is happening. If this continues, it could be the start of a broader extinction in the marine record. We know this is already somewhat occurring, but it could be much more significant and could lead to future climate scenarios that are not favorable for current marine life.

What will your Sloan Research Fellowship money enable you to do?

There are two topics I would like to focus on. One is having a better understanding of what typical background conditions are during periods without significant extinctions. We don't really know, because it's hard to get funding for times in our history when there's not significant climate or biological change. Hopefully, we can go into a few time periods and look at the background state to understand what is "normal."

The second thing we'd like to do is study various proxies, various isotopes, of one single sample or one time period to better illustrate what may be occurring in Earth's history. We haven't been able to do that to this point because it's expensive to analyze all these different elements at the same time.

Earth is a complicated system with many feedbacks. Each element fills in a portion of the picture, but no single element can tell us the entire picture. And that is the challenge — to be able to separate each one of their strengths and weaknesses to understand the story that each one is telling us.

What other elements do you want to look at?

Historically, the elements that have been done for this kind of work are molybdenum isotopes and uranium isotopes. Each element can tell us about different chemical reactions that occur following the depletion of oxygen.

How will learning about what took place hundreds of millions of years ago shed light on climate change today?

Climate change is due to simple chemical reaction. As we're burning fossil fuels, we consume ancient organic matter and oxygen, and it combines and makes carbon dioxide and water, which occurs in our combustion engines. That same chemical reaction we know is happening in ancient Earth when we have these climate changes. More and more work is showing that many of these changes were related to major volcanism. And it turns out that volcanic emissions have very similar reactions; some of them go right through coal and oil beds: They're actually burning up that organic matter and releasing carbon dioxide into the atmosphere. So, the chemical reactions are identical between ancient climate events and what's happening today, but these are very different events.

The timescales of these major volcanism events were much, much slower — they probably took half a million to a million years, in many cases. And obviously, what we're doing today is much quicker. The sequence of events from these ancient climate perturbations, or extinction events, can tell us at least what the progression of the environment will look like. That's our best window to understand future climate scenarios. It may not be a perfect analogue, by any stretch, but it's the best, or only, one we have. We can study the history and understand how these events transpired. And that might relate to what's going to happen, potentially, in our future.

We want to understand how the Earth responds to these climate events, what the feedback mechanisms are. The Earth is always changing, but those feedbacks to get it back to a state of pre-vulcanism were very slow. The Earth will be fine, but maybe without us, because these reaction rates are very slow.

Is there anything else you want to tell us?

When I was a college student, at the beginning I was a reasonable but not a great student. But then I had a quarter that was just awful. But that was actually the turning point in my academic life. I had five more quarters, and I decided that I was either going to do this or not. So I turned around. I was mostly on the Dean's List after that.

The point is, many people have really bad quarters or semesters throughout their undergrad history. It's more about what you do after that. That quarter totally killed my GPA. I thought, there is no way I'm going to grad school. But as it turns out, the person that nominated me for this Sloan Research Fellowship, Dr. Timothy Lyons, actually talked me into applying for grad school and took me as a grad student and eventually became my Ph.D. advisor and mentor.

That really changed my life. No matter where you are, you can really blossom if you put the time and effort into it, and find somebody who is willing to invest in you and mentor you. But it takes a lot of time and effort.

Story by Kristen Coyne