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Research vessel »Polarstern« during the »Mosaic« expedition in the central Arctic
Photo: Lukas Piotrowski / Heli Service International / dpa
For a year, scientists traveled the Arctic on the research vessel “Polarstern” and drifted with the ice. From 2019 to October 2020, the icebreaker collected unique data for the "Mosaic" expedition, which is now being gradually evaluated. More than 150 terabytes of information and 10,000 samples of ice, snow, water and air have come together, reports polar researcher Markus Rex from the Alfred Wegener Institute in Berlin.
Eight months after my return some results have now been presented. Accordingly, there is also a threat of a larger hole in the ozone layer over the Arctic. Expedition leader Rex said the shift had decreased there by a quarter. On the trip, in spring 2020, the scientists recorded the strongest decline in ozone levels in the arctic stratosphere, it said. At a height of 20 kilometers, ozone was sometimes no longer measurable. Rex has not yet given any reasons for the worrying ozone depletion. In the next few days, however, there should be more in-depth scientific publications.
Most recently, a decline in the ozone layer was measured, especially over the South Pole.
There the concentration fluctuates strongly depending on the season - for decades an ozone hole has formed over the Antarctic in the spring there.
While the hole usually closes in December, the ceiling tears open again in August and reaches its maximum size in October.
The ozone layer in the stratosphere is approximately 15 to 35 kilometers above the ground.
This protective coat is important for life on earth because it keeps the sun's harmful ultraviolet radiation off.
Chemicals released into the atmosphere are the main contributors to the retreat of the layer.
Chlorofluorocarbons (CFCs) are one of the most important. In the past, it was mainly released into the environment through refrigerators and spray cans.
In an agreement from the 1980s, the so-called Montreal Protocol, numerous countries committed to stop the production of such chemicals; an international production ban has been in place since 2010.
But a few years ago researchers were able to show that CFC emissions were increasing again.
Apparently the substance was released into the atmosphere by companies in China.
Exceptional weather, plus high chlorine concentration
Researchers from the German Aerospace Center (DLR) had already observed an ozone hole over the Arctic in March 2020.
As at the South Pole, in addition to the still high chlorine concentration from CFCs, certain weather conditions and seasonal fluctuations also contribute to the phenomenon.
For example, strong polar eddies were observed between the beginning of February and mid-March.
"The typical seasonal low pressure area in the stratosphere was extremely strong, stable and cold," the scientists write in a press release.
This favored ozone depletion, since chemical processes in certain stratospheric clouds made it possible to process atmospheric ozone.
The sun then provides the necessary energy for these reaction processes in spring.
But at that time the DLR researchers gave the all-clear.
In general, a recovery of the ozone layer has been visible for several years.
Therefore, if the existing protective measures are strictly observed, one can assume that the ozone layer will recover completely by the middle of this century, also in the polar regions.
It remains to be seen whether this will hold true according to the data from the »Polarstern« expedition.
Other results that have now been presented concern the retreat of the ice, a development that is no less worrying.
Accordingly, the researchers measured the largest decrease since records began, and the thickness has also decreased.
The ice is only half as thick as it was 130 years ago, and the extent in summer 2020 was only half as large as decades ago.
The ice cover closed much later in autumn than ever before, and the ocean was able to absorb large amounts of heat, according to Rex.
According to the scientist, it will only become clear in the next few years whether the ice in the Arctic can still be saved.
The region is about to trigger a tipping point.
Should the summer sea ice disappear completely, this would have far-reaching consequences for the earth systems and could further drive climate change.
joe
