Dr. Neil Fraser explains that warm water below the surface enters Greenland’s fjords in winter-time
DIMITRI LASCARIS: This is Dimitri Lascaris reporting for The Real News Network from Montreal, Canada.
As the world hurdles toward potentially catastrophic global warming, the scientific community has become increasingly concerned about the world’s largest ice sheets and the growing danger that their melting will cause devastating sea level rise. Of particular concern to scientists is the melting of the Greenland ice sheet. Scientists estimate that it contains enough water to raise global sea levels by an average of about six meters, or twenty feet. This would obviously render numerous major coastal cities largely uninhabitable and precipitate massive flows of desperate climate refugees. Now, a new study has revealed what many would have thought unthinkable until now, that parts of the massive Greenland ice sheet are melting, even in the frigid Arctic winter.
Now here to discuss this with us is one of its coauthors, Dr. Neil Fraser. Dr. Fraser is a specialist in ocean physics. In 2013, he began looking at the mechanisms linking ocean warming on the melt rates of the Greenland ice sheet, and he is now a post-doctoral researcher at the Scottish Association for Marine Science. His current research looks at large-scale North Atlantic circulation and its role in the climate. He joins us today from Oban, Scotland. Thanks very much for joining us today, Dr. Fraser.
NEIL FRASER: Hi, Dimitri. Thanks very much for having me.
DIMITRI LASCARIS: So before we get to your study, Dr. Fraser, I’d like to start by talking about the importance of the Greenland ice sheet to global sea level rise. Relatively speaking, how much is that ice sheet contributing to current sea level rise?
NEIL FRASER: Sea level rise can be partitioned into a few different factors. The main contributor is actually the expansion of the ocean as it warms. The thermal expansion of the water accounts for, I think, just under half of the observed sea level rise. After that, we have mechanisms for transporting land ice into the water, so melting of land ice, that’s the ice in terrestrial glaciers in places like the Alps, Himalayas, and mountain ranges which are melting. And then we’ve got the two ice sheets of Greenland and Antarctic ice sheet.
And the Greenland ice sheet has contributed more fresh water to the ocean over the last twenty or so years than the Antarctic ice sheet. So although the Antarctic ice sheet contains many times more ice than the Greenland ice sheet, it’s the Greenland ice sheet which has been losing the most ice over the last twenty or so years, and this seems to be increasing year on year, indicating that the Greenland ice sheet might be past some kind of tipping point whereby we’re not sure whether that ice will be recoverable.
DIMITRI LASCARIS: So please talk to us about the basic findings of the study you coauthored. What, in essence, did you conclude?
NEIL FRASER: So we know that the Greenland ice sheet is melting. And the patterns of melting indicate that it’s happening more around the edge than in the interior of the ice sheet. And at the same time, the ocean has been warming around Greenland. So this indicates that it’s the ocean temperatures increasing which causing the melting. However, the only place that we see direct contact between the ocean and the ice sheet are in these coastal fjords, so these long narrow inlets where the glaciers which drained the ice sheet, they flow into the fjords, and that’s where the ice sheet terminates, effectively. So you have these discrete locations where this huge ice sheet is actually in contact with the ocean.
It’s therefore critical that we understand exactly how warm ocean water gets into the fjords, how much heat is transported into the fjords via the ocean, and when and why that this is happening. So around coastal Greenland, typically the ocean is cold and fresh on top and then warm and salty underneath. And in the wintertime, we see strong coastal winds in Greenland which drive large waves, not at the surface, but at the interface between these two layers of the ocean. And this has the effect of pumping warm water in the lower layer in and out of the fjords as this interface goes up and down as the waves pass over.
So there have been observations previously of the water within these fjords, and they’ve indicated that these kind of processes would go on. However, it’s virtually impossible to do a research cruise to the fjords of Greenland in the wintertime due to the ice cover, icebergs, and adverse weather conditions. So what we’ve done is run a computer simulation of one of the major fjords of Southeast Greenland, and it’s allowed us to study how the wind and these large subsurface waves interact and quantify how much heat we might expect to be delivered over a winter season, and study in short time scales what these waves look like and how they move around, how they interact with the underwater topography. We found that the waves are highly dependent on–well, they’re affected by the rotation of the earth. So they go into the fjord on the right hand side and come out on the left hand side.
DIMITRI LASCARIS: Now we know, of course, that sea level rise itself could have catastrophic impacts on low-lying coastal areas, particularly those that are heavily populated, but something that is not discussed as much in the public domain are the effects on the Northern European climate of the release of massive amounts of cold, fresh water into the Northern Atlantic. You’re in Scotland, which is not all that far from the Southeastern coast of Greenland. Does the scientific community currently have a reasonable sense of how the climate of Northern Europe, including the United Kingdom, would be affected if the Greenland ice sheet were to disintegrate and release huge quantities of cold, fresh water into the Northern Atlantic?
NEIL FRASER: In the North Atlantic, we have what’s called the Atlantic Meridional Overturning Circulation, whereby warm water which is heated up in the tropics and flows northward at the surface, where it then cools down due to the atmosphere and sinks. And this drives this kind of conveyor belt whereby you have a northward flow towards the surface. And the whole ocean interior below the surface is very slowly flowing southward to compensate.
Now, if the Subpolar North Atlantic, which is the region, as you say, between kind of Greenland and Scotland and this kind of area, the kind of northern North Atlantic, if the salinity there decreases, then as that water cools, it won’t actually become as dense as it would otherwise, because both the temperature and the salinity contribute to the density. So it will cool down, making it more dense, but it won’t have the salt content to allow it to sink as far as it would have otherwise. And that’ll actually weaken this overturning, this conveyor belt. And the effect of that would be that the water being drawn northwards in the upper layer would slow down, and that would have, obviously, large effects for the European climate, because really it’s the North Atlantic Ocean and northward flow of warm water that keeps the European climate warm compared to the same latitudes on the other side of the Atlantic or in Canada.
DIMITRI LASCARIS: So despite the overall trend of global warming, in those circumstances, that particular part of the world, Northern Europe, could see a considerable cooling of the climate. Is that correct?
NEIL FRASER: Potentially, yeah, that’s right. The Greenland ice sheet does continue to accelerate in its melt rate, as we’ve seen, and we can expect the freshening of the Subpolar North Atlantic to have really drastic effects and slow down this AMOC, which is the conveyor belt bringing warm water north.
DIMITRI LASCARIS: So we’ve been speaking to Dr. Neil Fraser about a new study suggesting that parts of the Greenland ice sheet are melting in winter. Thank you very much for joining us today, Dr. Fraser.
NEIL FRASER: Thank you.
DIMITRI LASCARIS: And this is Dimitri Lascaris reporting for The Real News Network.