Ship leaving the sea ice in the Bering Sea. The "smoke" rising off the ocean, actually evaporation fog, illustrates the tremendous amount of heat emitted to the atmosphere over ocean compared to sea ice. Photo from the NOAA Photo Library.

The presence of sea ice has a substantial influence on the physical properties (temperature, salinity) of the water even months after the ice has disappeared.  The dissolved salts in sea water are not incorporated into sea ice as it forms.  Thus, when sea ice forms, saltier water is left behind under the ice.  This salty water is denser than the surrounding water and sinks. On the other hand, melting ice introduces fresher water to the surface of the ocean.  Ice floes move with the wind and the currents. In the Bering Sea, ice is usually formed in the northern part of the sea, and carried southward by the prevailing wind.  As the sea ice moves southward into warmer water, it melts along its edges.  (For a thorough discussion of sea ice in the Bering Sea, see http://www.beringclimate.noaa.gov/essays_mcnutt.html).

Fur seals on Bering Sea ice. Photo from NOAA's Arctic Theme Page.

We will measure the physical water properties (temperature, salinity) of both the ice and the water close to the ice edge.  Combined with observations made by other scientists on this expedition, these measurements will help us determine how the seawater is affected by the presence of sea ice and what water types are preferred by the plants and animals in the region.  We will also measure the amount of light penetration into the water and through the ice to determine how much light is available for plant photosynthesis.  And we will measure the speed and direction of the currents in the region.  In addition to measuring the physical conditions on this one expedition, we hope to continue making these measurements over the coming years to examine changes in the system from year to year.