Very cold parts of Antarctica are more vulnerable to meltdown than previously thought, according to new Dutch research. Because less snow falls in those places, meltwater lakes form on the ice more quickly in the summer. These can break up the ice shelves. In the long term, this could lead to additional sea level rise, with consequences for the Netherlands.
The world’s largest ice cap is located in Antarctica. This is largely on land, but also extends over the adjacent ocean along the edges. Those floating parts are called ice shelves.
Meltwater lakes form faster in the summer on the coldest ice shelves than on the warmer edges of the ice sheet. This is evident from new research by Utrecht University and TU Delft, which was published in a trade journal on Thursday Nature Climate Change.
Wat is een ijsplaat en waarom zijn ze belangrijk?
- IJsplaten zijn drijvende plakken ijs langs de randen van Antarctica. Ze zijn honderden meters dik.
- De grootste ijsplaten bevinden zich in baaien, zoals de Amundsenzee, de Weddellzee en de Rosszee. Dat zijn grote inkepingen waar de oceaan diep landinwaarts reikt, richting de geografische zuidpool.
- Grotere ijsplaten zijn ook erg koud. Je zou er dus niet veel smelt verwachten. Maar omdat daar juist minder sneeuw valt, kan afsmelting er ‘s zomers sneller beginnen dan gedacht.
- Als de ijsplaten afbreken, stromen achterliggende gletsjers sneller naar zee. Dat versnelt de wereldwijde zeespiegelstijging.
- Voor Nederland is Oost-Antarctica het belangrijkst. IJsplaten in dat deel van de ijskap zijn misschien minder stabiel dan gedacht.
That’s because Antarctica’s coldest ice shelves are much drier than other warmer ice shelves. That means there is less snow on the ice. Snow acts like a sponge on meltwater, lead author Melchior van Wessem of Utrecht University tells NU.nl. With a thin layer of snow, meltwater forms lakes more quickly.
Those lakes are darker than the ice and therefore heat up quickly in the sun. That amplifies the warming. The meltwater can also flow into fractures, causing the ice shelf to break up.
Meltdown is slow, but getting faster and faster
Where then is the tipping point for the melting of these cold and dry ice shelves? The Dutch researchers have calculated this using a model. When the average annual temperature rises above -15 degrees, the first meltwater lakes form on some ice shelves. That is 10 degrees colder than other ice shelves on which more snow falls.
This is not yet the case for the Rossplaat. According to the researchers, the tipping point may be reached later this century. Smaller ice shelves in western Antarctica are likely to have disappeared by then. For example, sea level rise is a slow process that is accelerating a little bit at a time.
Like parts of West Antarctica The Ross Sea is also seen as an Achilles heel of Antarctica. The sea forms a kind of wedge between the West Antarctic and the East Antarctic ice sheets. The latter contains much more ice and is a lot colder on average.
Rossplaat’s earlier disappearance is an old climate mystery
Geological research had already shown that the giant Ross Plate could collapse during warmer periods in the past. This was accompanied by several meters of sea level rise.
Given the cold climate of the Ross Plate, this was a mystery until now. Researcher Van Wessem cannot yet say whether the new findings about the formation of meltwater lakes provide an explanation for this. “It is certainly interesting for a follow-up study.”
East Antarctica is the most important for the Netherlands
The East Antarctic Ice Sheet also contains small indentations, such as the Amery ice shelf. And the conclusions of the Dutch researchers also apply to this, says Van Wessem. “Amery is a very cold ice shelf that is extremely dry. That shelf is so dry that many meltwater lakes can already be found there.”
“And so there are other East Antarctic ice shelves where the threshold for the formation of meltwater lakes appears to be low, or where it has already been reached,” says the researcher.
The research is important for the Netherlands. This is because mass loss from ice caps is not evenly distributed over the Earth. Ice loss in Antarctica leads to greater sea level rise in the North Sea than the same amount of ice loss in Greenland.
The enlargement via complex gravity effects additionally becomes even stronger when it comes to ice loss on East-Antarctica. Exactly the parts that were previously considered stable, but where the new research also detects small weak spots.
