Relatively recent research shows that in the summertime, thin ice and areas of open water allow sunlight to filter down to the water below. As a result, while a layer of ice-cold fresh water sits just beneath the sea ice, about 20 meters (65 feet) down there is a layer of denser, saltier water that has been gradually warmed by the sun's rays.
Blowing on polar water is less like blowing on a cup of tea and more like blowing on a layered cocktail. When the cyclone swept over the drifting ice floes, underside ridges churned up the water to bring sun-warmed seawater to the ice's bottom edge. The model suggests that during the cyclone there was a quadrupling of melting from below, and that this was the biggest cause for doubling ice loss during the three-day storm.
"We only looked at one big storm. If we want to understand how storms will affect the ice cover in the future we need understand the effect of storms in different conditions," said co-author Ron Lindsay.
More sunlight reaches the water in a year with unusually thin summer ice, such as 2012, so this process is a potential multiplier effect for sea-ice melting.
The results are of interest beyond understanding climate change. As sea ice thins and melts, economic and political concerns require better sea-ice forecasts to protect ships and instruments that might travel in those waters.
"One thing we are working on, and that needs to be included in future computer simulations, is how bigger waves created by wind blowing over more extensive open water help break up the sea ice into floes, and how these smaller floes respond to warm water," said co-author Mike Steele.
|Contact: Hannah Hickey|
University of Washington