Unlike its polar neighbor the Arctic Ocean, the Southern Ocean has seen relatively little warming in past decades. Some might take this as a sign that the region is unaffected by climate change, but researchers from the University of Washington and Massachusetts Institute of Technology believe they’ve found an oceanic pattern responsible for keeping temperatures in the Southern Ocean relatively stable.
A paper on the subject was published on May 30 in Nature Geoscience.
According to the researchers, centuries-old water is consistently being pulled up from the depths of the Southern Ocean. This is due to intense winds that push the ocean’s surface water northwards, thereby drawing up water from below. The old, frigid water can come from as deep as two miles.
“It’s really deep, old water that’s coming up to the surface, all around the continent,” said study author Kyle Armour, a University of Washington professor of oceanography and atmospheric sciences, in a statement. “You have a lot of water coming to the surface, and that water hasn’t seen the atmosphere for hundreds of years.”
The study leveraged data from the Southern Ocean Argo Regional Centre, which uses observational floats to track ocean heat.
“The old idea was that heat taken up at the surface would just mix downward, and that’s the reason for the slow warming,” said Armour. “But the observations show that heat is actually being carried away from Antarctica, northward along the surface.”
This moving warm water, the researchers found, ends up around the North Pole, an area marred by climate change. Over the last 100 years, the region has seen an air temperature increase of five degrees, and since the 1970s, there’s been a 14 percent decrease in Arctic sea ice, according to World Wildlife Fund. By 2080, the organization said summer sea ice is expected to disappear completely.
Armour said these regional shifts in warming are largely affected by ocean currents.
In terms of sea ice, the Antarctic is vastly different from the Arctic, as well. Since the 1970s, according to a NASA study, the maximum extent has remained relatively stable. In some cases, it’s even increased.
The intense winds that shift surface water northward also carry ice floes seaward. These ice floes, according to the study, create bands of ice, which range in width from 60 to more than 600 miles. They form a protective layer, which protects thinner ice closer to the continent from harsh winds, thus encouraging Antarctic ice growth.
