04/17/2020

Uncovering Antarctica’s Ancient Rainforest

16:17 minutes

a completely ice covered terrain. a large mountain stands in the back
Antarctica. Credit: Ariel Zych

Antarctica is the coldest place on the planet—the record temperature on the continent was nearly -140 degrees below Fahrenheit. But during the Cretaceous period, Antarctica was covered in a temperate rainforest. Instead of snow caps, the glaciers were swamplands.  A team of scientists wanted to know just how warm the temperatures were at the southernmost continent, so they drilled into the ice and found samples of 90-million-year-old roots, pollen, and spores (see video below). Their results were published in the journal Nature

Marine geologist Johann Klages, an author on that study, discusses what temperature the Earth would need to be to support such an environment in Antarctica, and how that can be used to create more accurate climate models. 

CT scan of the sediment core, showing sand at the top and tree roots and pollen with roots in-situ approximately 30 meters below sea bed. Credit: AWI/Bremen


Further Reading

  • Read the full study in Nature

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Segment Guests

Johann Klages

Johann Klages is a marine geologist at the Alfred-Wegener-Institut in Bremerhaven, Germany.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. On this planet, if you’re looking for a cold place, check out Antarctica, the coldest place on Earth. But listen to this, at one time– we’re talking 90 million years ago– there was a temperate rainforest in Antarctica. So instead of snow caps, there were swamp plants.

A team of scientists wanted to know just how warm the temperatures were at the southernmost continent, so they went there and drilled down deep into the mudstone. And what they found– their results– were published in the journal Nature. My next guest is here to fill us in on that story.

Johann Klages is an author on that study. He’s also a marine geologist and a research scientist at the Alfred Wegener Institute in Bremerhaven, Germany. Welcome to Science Friday.

JOHANN KLAGES: Yeah, thanks for having me. Hi.

IRA FLATOW: Let’s talk about this core. So you drill the core down, and what did you see in the core?

JOHANN KLAGES: Yeah, that was pretty exciting for us, because it was also totally unexpected. First, we had to go through 1,000 meters, about 3,000 feet water, and then drilled 30 meters into the sediment. And all of a sudden, in about 27 meters depth, we got into something very different and something that we didn’t expect at all.

The first thing we realized was that it had a completely different color that we have never seen before. And all of us from the science group, we went to Antarctica already several times, and we looked at hundreds of different cores. And that was definitely very unusual, very dark material, very fine grained. And there were some dark spots in there that we couldn’t really explain at first. But yeah, so that was the first impression– very different from all of what we saw before.

IRA FLATOW: So did you then realize you had drilled into a temperate rainforest?

JOHANN KLAGES: No, not at that time. I mean, at first, it was not really tropical. It was a temperate rainforest, so not that extreme. So a temperate environment, but still warmer than we have right now, let’s say, in Germany, and about the temperature New York City experiences today.

But yeah, we didn’t know that, of course not, because we had to apply a ton of different analysis to really dig into what we found. So that was very exciting. And that took another 2 and 1/2 years until we were there.

IRA FLATOW: Mm. And if you see photos of the South Pole today, all you see is the white ice. So how come there was a rainforest there where it’s not today?

JOHANN KLAGES: That’s an interesting question. But you have to realize before. So the latitude we drilled today is at 73 or 74 degrees south. And back then, it was even further south, so at 82 degrees south, only 900 kilometers away from the South Pole. So for us, that was crazy to realize.

And then, yeah, we had the same question. Like, how was that possible? And therefore, we wanted to first apply all these different methods, but then wanted to know what kind of climate conditions and climate dynamics were necessary to maintain such an environment that far south. And that was the time where we decided to get some paleoclimate modelers involved. And they really were able to tell us how the Earth, at that time, must have looked like.

IRA FLATOW: And what did they tell you? What was the climate like down there?

JOHANN KLAGES: It’s much more extreme than we expected, so far. I mean, we knew that the Late Cretaceous, and especially the time around 90 million years, was the warmest phase of the Late Cretaceous and also one of the warmest phases in the past 140 million years of the planet.

But we didn’t really have geological records or geological evidence from that fossils. And so we now knew that we had a very diverse environment with a lot of different plant species and very warm temperatures all year long. And so we put that as a target value for that model, so what is necessary in the climate system to meet these environmental conditions.

And it was crazy, because we needed at least 1,120 to 1,680 ppm CO2 in the atmosphere. So to put that in perspective, today, we have around 410, 420 ppm, so several times more. But not only that, also in order to meet that, in order to be able to simulate that in the model, we needed to assume that Antarctica was completely covered in vegetation and no ice was present at the time. So no ice sheets.

IRA FLATOW: And so where was the continent, itself, at that point to give you such a warmer climate?

JOHANN KLAGES: It was interestingly more or less in the same position it is today. And as I just said, it was, for this particular location we talk about, so where we took the core, it was even further south. So if we go back 90 million years ago, we have an interesting time.

So we have the phase where Gondwana was breaking up. So Gondwana is the last big supercontinent. 90 million years ago, Zealandia, so the submerged continent of Zealandia– only New Zealand now– is looking out the water. But Zealandia was just about to break up from West Antarctica. But Zealandia was drifting or moving much faster than West Antarctica did.

So West Antarctica basically remained in place more or less. And Zealandia was drifting away very quickly. And now, it’s several thousands of kilometers away from West Antarctica. But West Antarctica, itself, remained pretty stable and remained south. So, yeah, 90 million years ago, it was even further south, so even closer to the South Pole, where we drilled.

IRA FLATOW: That is amazing. So what you’re saying is, because we basically had the greenhouse effect going on there with all that CO2 in the atmosphere?

JOHANN KLAGES: We knew it was one of the last big greenhouse climates on the planet. We had several of those, but the Late Cretaceous greenhouse climate was the most extreme. And we knew that before. But what we now revealed is that it was even extremer than we saw it. Because the records we had so far– so geological records was really solid evidence– were from about, let’s say, maybe 70 degrees south, so 1,400 kilometers further north. And now, we are much further south.

So what we brought up from the current seafloor is by far the southernmost Cretaceous record available on the planet so far. And therefore, it’s a unique insight into the polar environment at that time. And when I say polar environment, it really means very close to the South Pole. And that was not available before.

IRA FLATOW: All right. Well, now that you’ve wetted my appetite, you have to tell me what you actually did see. What did you see in those core samples? What kind of trees and pollen and things like that?

JOHANN KLAGES: Yeah, that was exciting because I told you when we first saw the material on board– and some colleagues wanted to look at it immediately. So that means splitting the core. But some of us said, no, no, we definitely won’t do that because we already knew that something very special is inside them.

And you have to realize it only has a diameter of 6 centimeters. And it was 3 meters long, the Late Cretaceous section. So it’s a very valuable material. And therefore, we decided we’d bring it back home. And then, the first thing we did was CT scanning, so a 3D CT scanner. And that was the first time we really saw what’s going on in that core.

So when we first looked at this 3D data, we saw it as pristine and very well-preserved network of fossil roots. And these roots go down to the bottom of the core. And it’s within a matrix of very fine-grained material, so silty clay material. And this material was full of pollen and spores. and in situ, pollen and spores.

So no, we [INAUDIBLE] nothing. And that we already found out onboard that this is a completely entirely terrestrial assemblage of pollen and spores. And also, the material itself must have been completely deposited in a terrestrial environment. And so all the evidence that came together then– also the geochemical information and the sedimentalogical information– all pointed into the same direction that we discovered a temperate rainforest environment at 82 degrees south. So that was just amazing there.

IRA FLATOW: That is amazing. Now, you know, of course when we talk about going back 90 million years, we know– our listeners know– that that’s at a time when dinosaurs roamed the planet. Could there have been dinosaurs there, too?

JOHANN KLAGES: Yeah, it’s very likely that there were. I mean, I just told you how little material we got– 6 centimeter diameter and 3 meters long. So we have no direct evidence of dinosaurs or any formal life in there, but from records further north.

So for example, from an outcrop on the Seymour Island, which is in the Antarctic Peninsula, we have evidence for dinosaurs. For that particular location at 70 degrees south back then, we have evidence for that. And because it’s a similar environment, it’s very likely that they were also there. So it would be much weirder if no dinosaurs or insects or flying dinosaurs were present at the time.

IRA FLATOW: You talk about how much CO2 was in the atmosphere, causing global warming at that point there. Is there a lesson for us? You study the ice sheets. Is there a lesson for us here today?

JOHANN KLAGES: Yeah, there’s definitely a lesson. So right now, climate science and also paleoclimate science is lacking the understanding about these greenhouse climates in general. And so the only chance we have is to go back in time and get really empirical evidence about the climate dynamics during these greenhouse climates. Because right now, we’re on the good way to drift again into climate states that could be pretty similar and could drift into something like a greenhouse climate.

And therefore, we need to understand climate dynamics in these extreme times. So we call them [INAUDIBLE] member climates because these are really the most extreme climates we had on the planet so far. But climate models really have struggled to simulate the global climate dynamics during these times, especially because we don’t really have– well, so far, didn’t have records from polar regions and south polar regions for this time frame.

And now, we know it was probably much more extreme. And the temperature gradient between subtropical and tropical regions and the polar regions was much shallower than we knew before. And that has profound consequences for climate dynamics during that time. And we need to understand that, because as I said, climate models, if you force them with these high temperatures in polar regions, they simulate way too warm temperatures for a tropical or subtropical regions unrealistically high. So therefore, there must be a lot of bugs in these climate models, and these have to be evaluated and assessed in the future.

IRA FLATOW: And you think by drilling into the ice core, you can help fix those models?

JOHANN KLAGES: Yeah, because we can calibrate the models with that because we can tell the modelers how it was– which kind of values they have to target in their models. If this is not possible, at the same time, for tropical, subtropical regions, where we have a lot of records from this time frame, and now these new records from polar regions, then it’s not a good model. And therefore, it has to be re-evaluated and much more work needs to be done in order to meet that in a reliable way.

IRA FLATOW: I’m Ira Flatow, and this is Science Friday from WNYC Studios. What can the core samples tell us about the big ice sheets there now– the West and the East Antarctic ice sheets? You study the ice sheets, I know.

JOHANN KLAGES: Yeah. [CHUCKLES] Yeah, we are pretty lucky right now to have them. You have to imagine these huge ice sheets that we have right now. So the East Antarctic, West Antarctic, and Antarctic Peninsula ice sheets– so the four big ones– they act as gigantic mirrors for the radiation that comes from space and gets reflected back to space.

So therefore, this radiation is not really acting as a warming on the planet. So therefore, they have a huge effect for us right now to cool down the planet. And so the Antarctic ice sheet, which is by far the largest one on the planet, acts like a huge refrigerator for the planet right now. And therefore, they have a profound effect on climate right now.

But we have to say that not only atmospheric temperatures affect those huge ice sheets, especially in Antarctica right now. And this is another topic where I intensively work on– is that warm ocean waters and not surface waters, but deep ocean waters, that they spill onto continental shelves in Antarctica and melt the ice from below, so from underneath. And that was a process that was not really known 20, 25 years ago. And this, in combination– so a warming atmosphere in the future and also warming deep ocean waters– that will be a combination that won’t be good for the future.

IRA FLATOW: You’ve been there many times doing research in Antarctica. I was there once many years ago. It is a gorgeous, gorgeous place, right? What’s it like for you when you go back down? And if you go back down, if and when, and you’re doing more core samples, what’s the next thing for you?

JOHANN KLAGES: Yeah, so I’ve been there now four times. It’s just such a fascinating environment. It’s so huge and so beautiful and so quiet that you realize, OK, this is the planet without humans, I mean, besides the ones that are on the ship with you together. But you don’t see anything in any way affected by human behavior. So that’s one very amazing thing.

And when I work in Antarctica, we have long days on the ship. We work basically 24 hours in shifts. And once a day, at least, I need to go up on the upper deck and just realize how fascinating and surreal this environment around me is.

And the next steps for us now, it’s really to understand what the West Antarctic ice sheet, in particular, but also parts of the East Antarctic ice sheet can tell us, so that the past processes of these environments can tell us about the future development of the ice sheet. So getting to know most detail, the history of those very vulnerable parts of the ice sheet in the geological past, how this can tell us about its future behavior. And I think this is the main driver for us right now to work there.

IRA FLATOW: Well, we wish you great success and great luck, Dr. Klages.

JOHANN KLAGES: Thank you very much.

IRA FLATOW: Johann Klages, who’s a marine geologist and research scientist at the Alfred Wegener Institute in Bremerhaven, Germany.

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