Life in Arctic Sea Ice
As well as big animals like polar bears that hunt on top of Arctic sea ice, there is an extraordinary world of life living in the ice itself. David Thomas introduces these vanishing ecosystems and the challenges of studying them before they are gone...
David T - It's been very clear for the last 5-6 years or so that we really do have shrinking summer sea ice in the Arctic. This means that ice that normally lasted throughout many seasons is now almost totally disappearing in the summer. This is in contrast to the total ice in the Arctic in the winter period which is about the same extent as it's always been. When people in the media talk about Arctic sea ice loss, they're really talking about loss of sea ice in the summer months. There are predictions - the most catastrophic is that by 2013 there will be no ice in the Arctic basin in the summer. A more conservative estimate is that in the next 100 years there will be no ice in the Arctic basin in the summer. But there will always be Arctic sea ice in the winter and this is one of the things that tends to be forgotten. We are talking about long lasting ice rather than total ice extent in the Arctic.
So one of the consequences of there being less summer ice, and this is what the Arctic was renowned for in the past: having thick ice flows of 10 metres thick. This thick ice is actually going, so that the mean thickness of the ice in the Arctic Ocean is going down dramatically. One of the consequences of ice going is that especially snow covered ice reflects a lot of solar radiation and sea water, which is rather a dark body, absorbs radiation. So one of the things that's happening with Arctic sea ice is as there's getting more and more open water, more and more heat is absorbed, and this is actually increasing the rates, or is thought by some to be increasing the rate, of the melting of the Arctic ice.
Helen - We hear a lot about polar bears and walruses being the wildlife that suffer as Arctic summer ice disappears, but there's a lot more going on, not just at the top of the food web. What do we know about life under, and even in, the sea ice and why is it important?
David T - Sea ice was often thought to be a desert that's void of all life. We now know that there's actually a myriad of organisms from viruses to small crustaceans that live within the ice itself. There's a whole host of other, larger organisms that live in this very narrow band of the ice-water interface on the peripheries of ice flows and there's a host of organisms that are eating on the ice biology and the organisms of the ice-water interface like fish or larger crustaceans that are the basis of the food web for the seals and the more charismatic polar bears. So, there's a whole host of different habitats and whole ecosystems that are provided by sea ice, that are in turn are of a food source for the major charismatics that maybe catch the attention of the media a little bit more.
Helen - Presumably, we still have an awful lot left to discover about these sea ice ecosystems. There must be a lot of things we still don't know.
David T - I think it's right that sea ice research and the research into the organisms living in sea ice has been going on for the past 100 years, if you like. But it's only since we've had access to sophisticated research vessels, and being able to launch ice camps for weeks or months at a time, that we are actually being able to delve and to see just how fascinating this life around the ice is, and how important it is for fuelling the whole ecosystem. What's intriguing in this whole climate change and sea ice extent debate is it's hugely significant for the whole Earth system that this ice is going and that the surface oceans are warming as a result of there being less ice. And that in turn is melting the ice, but we don't really have much of an inkling of what all these changes are going to do to the biology within that system as well. We know that polar bears need ice flows from which to hunt, but what happens if the whole of the food web underneath those ice flows is taken out as well? So, we concentrate on the physical factors of thinking in Arctic sea ice change. We don't know that much about the biological factors, I think it's true to say.
Helen - Absolutely. And I guess, sadly, to some extent we're running out of time for these sea ice ecosystems. Is there anywhere in particular that you're focusing your research efforts at the moment?
David T - One of the intriguing things about this whole sea ice and climate change effect is that we concentrate on the Arctic because that's where tangible changes are taking place, but in the Antarctic, for instance, we're not noticing such major changes in sea ice, except in certain regions like the Antarctic Peninsula. But in the rest of the Antarctic, the total sea ice extent is rather stable, if not increasing slightly. So, it must be said that the climate change focus on the effects of climate change really are focusing in on the Arctic because I think time is running out. If, in 50 year's time, there is no summer sea ice and we don't really understand why the summer sea ice was important for the ecology, we're going to be a little bit bamboozled by that. I think we do have a sense that time is really running out in the Arctic for actually understanding how important these systems are.
Helen - I guess really the big question is, what's going to happen in the years ahead? Do you have any thoughts on that?
David T - I don't think there's any argument - I'm fairly convinced - that we are going to reach a stage where Arctic sea ice is going to be absent in the summer months. This means that there's going to be much larger periods of open water. Ice is a very good absorber of light; you put a slab of ice a little thick over the ocean and a lot of light gets cut out. So if there's no ice, potentially, there will be increases in the amount of productivity or primary production of the unicellular phytoplankton. That would mean that maybe there is more food for the copepods and the crustaceans to eat and therefore, more for the fish. Now in the most simplistic terms, we could say that the productivity of the Arctic could actually go up but we don't know how important the organisms within the sea ice are at the moment for their contribution to productivity in total. I think there's a lot of guess work going on and people don't really know. What we do know is that the ice that will be there will be thinner, more light will get through to the water so therefore productivity in the ice and of surface waters could potentially go up.
Find out more
Professor, School of Oceanography, Bangor University
Biogeochemistry of Arctic sea ice.
Arctic sea ice News & Analysis.
National Snow and Ice Data Centre