editor Climate and Energy
Since satellite measurements began in the 1970s, there has never been so little sea ice around Antarctica as it is today. While the summer season is not over yet, the record has already been broken, reports the National Snow and Ice Data Center.
The area covered by sea ice has shrunk to about 1.9 million square kilometers. As a result, a large part of the ocean around mainland Antarctica is currently ice-free.
The amount of sea ice at both the North Pole and the South Pole is closely monitored by climate scientists. Still, it is too early to say whether the current developments around Antarctica are worrisome and indicate an acceleration of melting. The new record may also have been caused by natural variations.
Difference North and South Pole
Until recently, the ice in the North Pole in particular continued to melt; since measurements began, the area of sea ice there has decreased by about half. The ice is also less thick now. If you combine thickness and surface area, about 75 percent of all sea ice there has disappeared.
Incidentally, this does not cause sea level rise, because that ice floats on the Arctic Ocean. It does, however, mean that solar radiation is reflected less by the ice and instead warms up the ocean water. This is one of the reasons why this area is warming up (much) faster than the rest of the world.
Around Antarctica, the amount of sea ice remained almost constant for a long time. In winter, a maximum record was even broken a few years ago. Many factors therefore influence the amount of sea ice around Antarctica, says climate scientist Richard Bintanja of the University of Groningen and the KNMI. “It is a complex issue, which makes it difficult to say whether this situation is alarming.”
In addition to global warming, caused by greenhouse gas emissions, there are other processes that influence this. Such as the interaction of the air circulation around Antarctica with the stratosphere and even the amount of ozone. Bintanja: “All these effects play a role, and they all affect the amount of sea ice around Antarctica. Therefore, we cannot exclude that this record low is caused by natural variability.”
It is true that the amount of sea ice affects the ice shelves that surround Antarctica. Ice shelves act as a kind of plug or cork and, as it were, hold back glaciers on the mainland. Scientists expect that if those ice shelves also disappear, glaciers can flow more quickly into the sea. Sea ice ensures that the ice shelves come into less contact with wave action.
“Sea ice has a nice property, namely that it dampens waves,” says Bintanja. “I’ve been there a few times, and I was always happy when we sailed through an area of sea ice, because then there were less high waves.” Sea ice is a few meters thick frozen sea water, which shows large differences in summer and winter. The ice shelves, which are attached to the mainland, are regularly a few hundred meters to even a kilometer thick.
These ice shelves are incidentally more vulnerable to further global warming than previously thought, researchers from TU Delft and Utrecht University concluded in a study last month. Their findings show that lakes of meltwater can form more quickly on those ice shelves. And such lakes are bad news. If an ice shelf has cracks, the water from those lakes can flow into the cracks and shatter the ice shelf in a short time. More than 60 percent of the ice shelves in Antarctica have such cracks. If melt lakes are created everywhere, they may therefore break up more quickly.
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