Thinner Arctic Ice Sparks Massive Algae Bloom

When scientist Kevin Arrigo set out to lead a joint Stanford University-NASA expedition into the Chukchi Sea between Russia and Alaska, he believed the ecosystem below the Arctic pack ice was a watery desert. What he found under the ice though was an algae bloom spanning at least 60 miles. He talks with Audie Cornish about the discovery.

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AUDIE CORNISH, HOST:

Scientists on an expedition off the coast of Alaska found something they had long thought was impossible. Beneath two, three, even four feet of ice in the frozen Chukchi Sea, they found algae. Not just a little but a bloom that ran at least 60 miles wide. The team just published its findings in the journal Science.

Here to tell us why it's a big deal is the man who led the expedition, Kevin Arrigo, professor of environmental earth systems science at Stanford University. Professor Arrigo, thanks for talking with us.

KEVIN ARRIGO: Thanks for having me.

CORNISH: So why is this so surprising?

ARRIGO: Well, it's surprising because ice is a really good barrier to light. Generally we assume whenever there's ice on the ocean, there's not going to be any light underneath it and plants can't grow. Clearly that's not the case in the place where we studied in the Chukchi Sea.

CORNISH: So is this a new phenomenon or just newly discovered?

ARRIGO: We don't really know. We do know that in the place where we discovered it, it is new. Twenty, 30 years ago, if we sampled that same area the ice would have been probably nine, 10 feet thick. Today, the ice is a lot thinner. And not only is it a lot thinner, it's also covered in melt ponds. And what the melt ponds do is they allow lots more light to be transmitted into the ice. It makes the ice a lot less reflective and a lot more light penetrates into the water so that the phytoplankton underneath can grow.

CORNISH: So, help us understand this ecosystem then. I mean, is this a good thing or a bad thing that this phytoplankton is growing under the ice?

ARRIGO: It's not a really a good or a bad thing. It's a different thing and that's sort of the important part. It's going to be really dependent how the system responds to that particular change.

CORNISH: And when you mean system responding, it means what kinds of animals will be eating more of this, eating less of this, whether it'll hurt other species - that sort of thing?

Well, that's right. You know, there's a certain amount of food that gets produced in places like the Chukchi Sea and there's a limited amount of nutrients, and so there's only so much to go around. There's a lot of animals that feed off the bottom. And most of the stuff that's going to be produced under the ice is probably going to sink to the bottom. So, things like walruses and gray whales, they feed off of things at the bottom and they'll probably do really well.

Other animals that feed more in the water - seabirds that eat small fish - they may actually do worse under this situation, because more of the food is going to be going to the bottom feeders, as opposed to them.

Do we understand yet what this means? I mean, what is the kind of take away from this discovery?

ARRIGO: Well, I think there's a few take away messages. First of all, for me at least and for my group, it's really gratifying to know that, you know, we can work in systems for 20 years and we can go out and we can be surprised. And this was a really surprising finding. This is one of the things where if someone had asked me about beforehand, I would've told him it was impossible. And as we were seeing it, we were convinced that there was something wrong, that our instruments were wrong, this couldn't be here.

The other thing is, though, it's really important for us to understand how this earth we live in is going to change in the face of ongoing changes in climate, and other things that are going on. We got to go to those places is that are most sensitive to those changes. The Arctic is one of them.

And I think seeing something like this that was totally unexpected and totally unanticipated, I think is a real wake-up call for us that we really need to get a better handle on how these systems work today, so that we can understand better how they might respond in the future.

CORNISH: Kevin, thank you.

ARRIGO: Oh, you're welcome. Thank you very much.

CORNISH: Kevin Arrigo is professor of environmental earth systems science at Stanford University.

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