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Science

Dartmouth Researchers Analyze Data From Arctic Expedition

The icebreaker expedition in the Actic.
Professor Donald K. Perovich / Dartmouth
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After more than a year intentionally stranded in the Central Arctic, a research icebreaker returned to her homeport last month in Germany.

The Multidisciplinary Drifting Observatory for the Study of Arctic Climate, or more easily said MOSAiC expedition, was a record breaker for both the trip itself and the huge amount of data it collected.

Now, a team of Dartmouth engineers, along with other researchers around the world, begin the process of analyzing and interpreting all of that information. NHPR's Morning Edition Host Rick Ganley spoke with Dartmouth Engineering Professor Don Perovich, who is the co-lead for MOSAiC's sea ice team.

Rick Ganley: Well, Don, can you explain what this expedition set out to do?

Don Perovich: Yeah, MOSAiC was 10 years in the planning, and it was motivated by an overarching science question: what are the causes and consequences of an evolving and diminished Arctic sea ice cover? And what that question is really saying is there have been tremendous changes over the past few decades in the Arctic sea ice cover, and in fact, it serves as an indicator of global climate change. And we wanted to go up and spend a year drifting with the ice to take a series of observations to help us first, observe the changes, and then understand them.

Rick Ganley: So what were you monitoring? What were you observing? Was it ice flow, the thickness, temperature? What was it you were looking for?

Don Perovich: All that and more. There were five teams that made up MOSAiC, teams studying the atmosphere, sea ice, the ocean, ecosystems and biogeochemistry. And our idea was to get as completely set as measurements as possible. And it's important to remember that while this was a field experiment, it was deeply integrated with the modeling community. When we were planning MOSAiC, we went to climate modelers and said, what observations do you need to improve your models, and we'll go out there and be sure to make them.

Rick Ganley: There's something like 100 terabytes of data from all this observation that you did over the course of more than a year. So who's analyzing it and what exactly are they doing with all that data?

Rick Ganley: A couple of people say, well, gee, now that MOSAiC's over, what are you going to do with your life? Well, the fun is just beginning. I mean, this incredible data set will be studied for decades. And at this stage, the first task is for us to analyze our data, do quality control and get it into an archive. From the very beginning, we've recognized with MOSAiC that the data are the legacy of the project, and we want to make this data accessible as possible to a wider group of scientists as we can and also to convey what we learned to the general public.

Rick Ganley: Now, what is your team at Dartmouth doing?

Don Perovich: We're a sea ice team and we're looking at a few key questions. One, we want to understand the snow on sea ice. And just a quick primer, it's so cold in the Arctic Ocean that the ocean freezes forming sea ice. And this ice cover is maybe 5 to 10 feet thick. And during part of the year, it's covered by snow. We want to understand how deep that snow is, how it moves around and what its impact is on ice growing in the winter and melting in the summer.

Another task we had was to try to understand a concept called the mass balance of the ice. And that's just simply how much does it grow in the winter and how much does it melt in the summer? And in particular, how much of it melts on the surface of the ice and how much melts on the bottom the ice? And that allows us to attribute whether these changes that we observe in the ice are being driven mainly by the atmosphere, or by the ocean or both.

And finally, the third element of our project. Well, it was one of my favorites, and that was to study what happens to sunlight. Of the incoming sunlight, how much gets reflected by the ice cover, how much gets absorbed in the ice and how much gets transmitted into the ocean? And if we look at snow covered ice, it's a great reflector. It reflects around 85 percent of the sunlight. If we look at the ocean, it's a poor reflector. It reflects less than 10 percent of the sunlight. And so changes between ice in the ocean can have a feedback, where as you expose more ocean, you put more sunlight absorbed, you get more melting, you expose more ocean. And that was one of the key things we wanted to look at, because you need to be able to treat that feedback properly in models.

Rick Ganley: What makes the Central Arctic the epicenter for this kind of climate research?

Don Perovich: Well, I think one of the things that was exciting about MOSAiC was this opportunity to get into part of the Arctic where there hasn't been much work done. And also, it was a chance to study the new Arctic Ocean. There have been tremendous changes in the past couple of decades to the Arctic. There's less ice. The ice that's there is thinner. And we needed to go in to assess those changes.

Rick Ganley: Can you put this in context for us historically, what we are seeing in the Central Arctic now?

Don Perovich: We have a good satellite record of, you know, how far the ice goes out in a given area, how much ice there is compared to ocean. We have a good record going back 42 years. And what we've seen is that there has been a decrease over that period of around 13 percent per decade. One way to look at is at the end of summer, it's when the ice reaches its minimum extent. So if we roll back to 1980, the area covered by sea ice at the end of the summer was roughly the size of the continental United States. If we jump forward 40 years to 2020, it's as if the entire United States east of the Mississippi River had melted, plus the states from Minnesota down to Louisiana, plus North Dakota, South Dakota, Nebraska and Oklahoma.

So there's just been a tremendous change in the area covered by ice. And one of the things MOSAiC is working to understand is what's driving those changes and what are the consequences of those changes. For example, when we remove all that ice, what's the impact on ecosystems? And the Arctic is a cold, harsh environment, but it's also host to a rich marine ecosystem that's intimately connected to what's going on with the ice, and the atmosphere and the ocean.

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