“We can think of the ocean being built up in all these layers, and the structure of those layers is based on how salty and how warm the water is etc. In most of the world, the warmest water sits near the surface, but in the Arctic, salinity is a more important driver, so cold water ends up on the surface instead,” says Sam Brenner, a PhD student with Professor Thomson and Affiliate Associate Professor Luc Rainville, also with the University of Washington’s Applied Physics Lab.
Research measuring effect of loss of sea ice and mixing of warm and cold water
Beneath this cold-water layer lies warmer waters, but there is little mixing between these two layers, partly thanks to sea ice. “The ice acts as a lid, insulating the ocean from the wind, but as the ice breaks up, the wind can push on the ocean more, and all of that momentum from the wind can make its way into the ocean, causing turbulent mixing of this warm water that’s underneath the cold layer,” Brenner explains. “As that water gets warmer, and as the ice loss advances, we have this potential for a feedback mechanism where you’re mixing more of that warm water up to the surface, and that melts more of the ice.”
An ADCP capable of measuring the ice’s “geometry” as well as velocity and direction
Sea ice moves with wind and currents, pushing it in and out of warm-water patches. While the ice’s size plays a role in its movement, so too does the ice’s geometry – its rugosity – beneath the sea surface. In essence, rugosity can influence the friction between the ice and water, which in turn influences its movement, how it grows and how it melts. Using the Signature500 ADCP, Brenner hasn’t just been able to “map” the ice’s geometry, but also the velocity and direction the ice is moving – in remarkable detail.