The West Antarctic ice sheet is sitting under water. This is key to understanding the evolution of the ice sheet and how the rising sea floor might even help to slow down ice melt in this part of Antarctica.
Our recent study published in Science showed that as the glaciers of West Antarctica retreat, the land beneath is rising much faster than anyone thought. Up to five times faster, meaning that in 100 years the land will be up to 10 meters higher than it is today.
Our findings were actually about the structure of the Earth beneath a small portion of Antarctica, which you can read more about here. But media headlines (here, here, here, and here) were quick to focus on the startling and thus far, not well known, implications of the results: Could this process slow down West Antarctic ice melt and even stabilize the ice sheet?
The theory is that the rising land (bedrock) could reduce or even prevent ice retreat in the most sensitive glaciers of West Antarctica. But, while we know that it ‘could’ happen, we do not know how effective it would be in this specific region.
Here, we can at least examine how this process works and explain some of the factors involved.
West Antarctic ice sheet is sitting under water
The Antarctic continent is the least explored continent on the planet: Inaccessible and inhospitable. It is mostly covered by a thick layer of ice reaching a thickness of four kilometres, which makes it almost impossible to directly observe the bedrock beneath.
That said, West Antarctic geology is very interesting, ranging from “relatively recent” volcanism to a rift system. This makes the subglacial landscape extremely complex, with high, steep peaks, and deep troughs and valleys (see the image below).
Most of the West Antarctic Ice Sheet is immersed in the ocean and sitting on the sea floor (technically we say that it is grounded below sea level).
The huge weight of the ice has shaped and ‘bent’ the surface of the Earth beneath, so now the ice rests on a bowl-shaped seafloor that reaches 2,500 meters below sea level.
Underneath Antarctica is a complex and varied topography. While the West Antarctic Ice Sheet is actually grounded below sea level. (Image: Valentina R. Barletta / Author Provided)
Here, the ice sheet is exposed to warm ocean currents. This is why we call it a “marine ice sheet”.
Since the 1960s, scientists have recognized that the peculiar subglacial landscape makes the ice here susceptible to the action of a warming ocean, which causes the ice to become unstable and could eventually lead to its collapse within centuries to millennia.
Some glaciologists think that collapse is already underway (also here). This would be bad news, because if all the ice of the West Antarctic Ice Sheet were to melt it would add three meters to average global sea level, affecting every coastline in the world.
In short, any changes in the bedrock landscape hosting the ice can in principle have a great impact in the ice evolution. The land uplift that we measure is one of the most important changes occurring to the sea floor below the West Antarctica Ice Sheet.