Growth Of Antarctic Sea Ice A Warning Bell For Coastal Flooding
The stunning outward spread of ice floes atop the seas surrounding the South Pole has been caused by cold freshwater flowing out of melting Antarctic glaciers. (Shifting winds may also be playing a role in the breaking of previous Austral sea ice records.) That melting is forming layers of unusually cold and relatively salt-free surface waters in the region, the tops of which are being frosted with layers of blue-white ice.
Those layers of cold water could recast the southern stretches of the influentialAtlantic Meridional Overturning Circulation, which ferries water between tropical and polar regions, all the way from the Arctic to the Antarctic — with planet-churning consequences. Recent modeling indicates that these cold-water layers also formed as Antarctica melted during the prehistoric past, when they blocked warm water, which gets carried by deepwater currents to the Southern Ocean from the tropics, from surfacing.
At the surface, that warm water normally sloughs its excess heat into the atmosphere, cools down, then flows back north — typically a standard feature of the Atlantic’s circulation system. Without that Antarctic upwelling, the new study, which waspublished in Nature Communications, warns that the ice sheet is in danger of beingmelted from beneath at a hastening pace.
“We found out that if you put a certain amount of freshwater into the Southern Ocean around Antarctica, then basically it reduces this overturning — it reduces the upwelling of that warm water,” said the study’s lead author, Nick Golledge, a scientist at the Victoria University of Wellington’s Antarctic Research Center in New Zealand. “All that heat just gets trapped at a depth where it can melt the base of the ice shelves and the grounded ice that’s sitting in the ocean.”
The paradox of the expanding Antarctic Sea Ice is rather well explained. And it doesn't bode well for the future.
The stunning outward spread of ice floes atop the seas surrounding the South Pole has been caused by cold freshwater flowing out of melting Antarctic glaciers. (Shifting winds may also be playing a role in the breaking of previous Austral sea ice records.) That melting is forming layers of unusually cold and relatively salt-free surface waters in the region, the tops of which are being frosted with layers of blue-white ice.
Those layers of cold water could recast the southern stretches of the influentialAtlantic Meridional Overturning Circulation, which ferries water between tropical and polar regions, all the way from the Arctic to the Antarctic — with planet-churning consequences. Recent modeling indicates that these cold-water layers also formed as Antarctica melted during the prehistoric past, when they blocked warm water, which gets carried by deepwater currents to the Southern Ocean from the tropics, from surfacing.
At the surface, that warm water normally sloughs its excess heat into the atmosphere, cools down, then flows back north — typically a standard feature of the Atlantic’s circulation system. Without that Antarctic upwelling, the new study, which waspublished in Nature Communications, warns that the ice sheet is in danger of beingmelted from beneath at a hastening pace.
“We found out that if you put a certain amount of freshwater into the Southern Ocean around Antarctica, then basically it reduces this overturning — it reduces the upwelling of that warm water,” said the study’s lead author, Nick Golledge, a scientist at the Victoria University of Wellington’s Antarctic Research Center in New Zealand. “All that heat just gets trapped at a depth where it can melt the base of the ice shelves and the grounded ice that’s sitting in the ocean.”
The paradox of the expanding Antarctic Sea Ice is rather well explained. And it doesn't bode well for the future.