Sergio Pitamitz//VWPics/AP
Larsen Inlet in the Weddell Sea, Antarctica.
CNN –
According to a report, deep-sea waters in Antarctica are warming and shrinking, potentially having far-reaching consequences for climate change and deep-sea ecosystems.
“Antarctic Groundwater” is the coldest and saltiest water on the planet. These bodies of water play a critical role in the ocean’s ability to act as a buffer against climate change by absorbing excess heat and human-caused carbon pollution. They also distribute nutrients across the ocean.
But in the Weddell Sea on Antarctica’s north coast, that vital body of water is diminishing due to long-term changes in winds and sea ice, according to the study released Monday by the British Antarctic Survey.
Scientists used decades of data from ships and satellites to estimate the volume, temperature and salinity of this part of the deep Antarctic Ocean.
“Some of these sections were first visited as early as 1989, making them some of the most extensively sampled regions in the Weddell Sea,” said Povl Abrahamsen, physical oceanographer at BAS and co-author, in a statement.
They found that the volume of cold groundwater has shrunk by more than 20% over the past three decades. They also found that ocean waters deeper than 2,000 meters (6,600 feet) have been warming four times faster than the rest of the global ocean.
“We used to think that changes in the deep sea could only take place over centuries. But these important observations from the Weddell Sea show that changes in the dark abyss can occur within a matter of decades,” said Alessandro Silvano of the University of Southampton in the United Kingdom, co-author of the study, in a statement.
The reason these deep waters are shrinking lies in changes in sea ice formation caused by weaker winds, the study found. Stronger winds tend to push the ice away from the ice shelf, leaving open areas of water where more ice can form. According to the study, weaker winds have caused these gaps to be smaller, slowing sea ice formation.
New sea ice is critical to the formation of the very cold, salty water in the Weddell Sea. When the water freezes, it displaces salt, and the denser the saltwater becomes, the deeper it sinks to the ocean floor.
The changes in these deep waters can have far-reaching consequences. They’re an important part of global ocean circulation, transporting human-caused carbon pollution to the deep sea, where it lingers for centuries, Silvano said. When this deep circulation weakens, “the deep ocean can absorb less carbon, limiting the ocean’s ability to mitigate global warming,” Silvano told CNN.
The oceans have absorbed more than 90% of the world’s excess heat since the 1970s and absorb almost a third of human-caused carbon pollution.
This cold, dense water also plays an important role in oxygenating deep sea waters. How and if deep ecosystems might adapt to less oxygen “is unclear,” Silvano added.
Holly Ayres, a researcher in the Department of Meteorology at the University of Reading in the UK who was not involved in the study, said the BAS research represents an advance in our knowledge of Antarctica’s deep sea waters.
“The combination of decades of ship-based observations and satellite data is a major advance in our understanding of the formation process and could aid in our understanding of how Antarctic groundwater will form in the future,” Ayres told CNN.
While the changes identified in the study are the result of natural climate variability, climate change is also impacting Antarctica’s deep waters.
In a March study, scientists found that melting ice is thinning ocean salinity and slowing the circulation of deep-sea water in Antarctica. Failure to limit pollution caused by the planet’s warming could disrupt the circulation of deep-sea water, with potentially devastating consequences for the climate and marine life, the report says.
The new BAS study is “an early warning,” Shenjie Zhou, oceanographer at BAS and lead author of the study, told CNN. “The ongoing changes in the deep water layer in Antarctica are already happening and they are not going in the direction that we want.”