interview by Eleonora Milazzo – ACCEL European Fellow
- How do you assess the risks connected to changing ice conditions in Arctic ecosystems? Why are ice sheets important?
In the last 20 years the Arctic has seen a warming that is around double the global average. We expect the polar regions and, particularly the Arctic to be more sensitive than the rest of the world. This is known as polar amplification.
The impacts of that are a reduction of Arctic sea ice and snow cover over land. The marginal ice zone (the edge of the sea ice) is a very productive area. As sea ice changes, ocean productivity will be affected. Another key impact is that the sea ice acts as a thermal and moisture barrier between the ocean and atmosphere. If you remove the sea ice you start getting more photosynthetic activity in the upper part of the ocean. Snow cover acts as a suppressant for primary productivity of the land and reduces the amount of radiation reaching the soil, shutting down productivity. If you remove that snow cover that will also influence primary productivity over land as well.
Concerning ice sheets, in the Arctic there is one major ice sheet, Greenland, which is the largest ice mass in the northern hemisphere and the largest island in the world. The ice sheet tends to respond relatively slowly in terms of changes in area. Short-term impacts have more to do with the run off coming with the ice sheet reduction. There will be much more fresh water input into the fjords and coastal water. That will have an impact on the nutrient content of the costal waters and also some impact on ocean stratification.
- Changes in ice conditions are no bad per se. Is there any positive or at least not harmful effect of these changes?
These changes are not necessarily good or bad if we’re talking about sea ice. I think there are some effects that are not necessarily harmful, like increased nutrients to coastal waters. If you have increased melting from land ice and chemicals material at the base of the ice enters the ocean, this may increase productivity in coastal water. That’s not necessarily a bad thing but it will have a certain influence on the ecosystem.
As the ice decreases, you got more solar radiation acceleration. This is not harmful but will have some impact as well. A secondary human induced effect is that as the perennial sea ice reduces in area, we will see increased shipping. Ships can save up three thousand miles going to Asia through the Arctic. That has several potential harmful consequences. First of all, ships are one of the dirtiest forms of transport that exist. When they are travelling to the Arctic they generate quite a lot of black carbon that may be deposited over sea ice and over glaciers, affecting the albedo of the snow cover. In addition, ships tend to empty their ballasts as they’re travelling across the ocean. They introduce foreign species in the Arctic Ocean.
- Greenland ice sheet has begun to decline. The global impact of this phenomenon will be felt on a timescale of centuries. What are the consequences for now?
The really dramatic effect that we may see in Greenland is in a time scale of centuries and is in terms of sea level. In the short term, the key effect is the increase of fresh water fluxes not just in the Arctic Ocean but also in the North Atlantic. That may effect stratification in the surface waters and it may also have some influence on ocean circulation in the short term.
The jury is out on to what extent run off and fresh water fluxes in Greenland may influence ocean circulation on a larger scale. One of the things that we need to know is what proportion of these changes is due to anthropogenic effect and what proportion is due to natural variability. The evidence is becoming clear that there’s a significant signal for anthropogenic force. Reversing that will require a global commitment to curb greenhouse gas emissions.
Disclaimer: The views and opinions expressed in this article are those of the interview subject alone and do not necessarily reflect the official views of ACCEL, ELEEP, Ecologic Institute, or the Atlantic Council.