According to a team of researchers, global warming accelerates the great ocean current around Antarctica. The reason for the acceleration of the so-called circumpolar current is that large ocean areas absorb a considerable part of the heat caused by humans, write the researchers led by Jia-Rui Shi from the Scripps Institution of Oceanography in La Jolla, California in the trade journal Nature Climate Change. The researchers analyzed the development of this current with the help of satellite data and floating buoys from the Argo program. These are distributed in all oceans and can sink to a depth of 2000 meters and then rise again.
According to the Intergovernmental Panel on Climate Change, the oceans have so far absorbed more than 90 percent of the additional heat generated by man-made climate change. This buffers the global warming. However, this makes the water warmer and expands, which contributes to the rise in sea levels. In addition, according to the IPCC, the oceans contain 20 to 30 percent of the carbon dioxide produced by humans, which makes their water more acidic.
The water north of the stream absorbed a lot of heat
The circumpolar current always flows to the east around the southern continent and thus connects the Atlantic, Pacific and Indian Oceans. It is considered a global conveyor belt that influences heat transport and material cycles in all oceans. The water north of the stream absorbed more man-made heat and warmed up more than the water in the stream itself and that south of it, the researchers write. Therefore, the temperature difference at the circumpolar current has increased – a factor that always leads to acceleration in ocean currents. In particular, the northern part of the river has accelerated.
“The circumpolar current is primarily driven by the wind, but we have shown that, surprisingly, the change in speed is primarily due to the change in temperature gradient,” says co-author Lynne Talley, also of the Scripps Institution. According to the researchers, the westerly winds in the region, which are also intensified by climate change, play an additional role. Persistent ocean warming could further increase the speed of the circumpolar current, writes the team.
A change in the current can have far-reaching effects on the climate
A team from the Alfred Wegener Institute (AWI) in Bremerhaven only reported this year that the electricity flows particularly quickly during warm periods. Among other things, it analyzed a 14-meter-long drill core with sediments that had been deposited over the past 140,000 years. This gave the researchers information from the last ice age, which began 115,000 years ago and ended 11,700 years ago, and also from the last warm period. Result the one in the journal Nature Communications presented study: During the last warm period the circumpolar current was faster than it is today.
“At the height of the last warm period from 115,000 to 130,000 years ago today, it was on average 1.5 to 2 degrees Celsius warmer than today. The circumpolar current could therefore accelerate in the course of global warming in the future,” says co-author Frank Lamy. That would have far-reaching effects on the climate. The Circumpolar Current shapes other ocean currents such as the Gulf Stream, which helps determine the climate in north-western Europe. “The new study agrees very, very nicely with our results,” said Lamy.