Melting ice shelves in Antarctica are weakening global ocean currents.
Elephant seals, armed with ocean sensors, have revealed that freshwater from melting sea ice is mixing with the cold, salty water at the bottom of the Antarctic. According to a new study published in Nature, the dilution of this bottom water could hamper the ability of deep ocean currents to regulate global temperatures.
"Antarctica and the Southern Ocean are like a beating heart, producing deep and powerful currents of cold water that drive global ocean mixing and regulate atmospheric temperatures." Study lead author Guy Williams, from the Institute of Marine and Antarctic Studies and Antarctic Climate and Ecosystems at the University of Tasmania, explains in a press release.
"These currents begin with intense sea ice formation around the Antarctic continent in winter, which creates cold, salty and dense water that sinks and flows away from the continent in large volumes.”
But according to Williams, the addition of freshwater to this Antarctic bottom water weakens it, thereby slowing the production of the ocean currents, which may ultimately lead to catastrophic changes in the global climate.
Elephant seals are skilled divers, sometimes reaching depths of a few thousand feet. By fitting elephant seals with instruments that relay information about water temperature and salinity back to land, the researchers observed that the water in Prydz Bay, which makes contributions to the Cape Darnley Bottom Water, “is less salty and dense due to the influence of nearby ice shelves," says Williams.
As the rate of sea ice melting around Antarctica continues to increase, global ocean currents are expected to weaken.
The authors write that the result of their two-year study “highlights the susceptibility of Antarctic bottom water to increased freshwater input from the enhanced melting of ice shelves, and ultimately the potential collapse of Antarctic bottom water formation in a warming climate.”