The Importance of Sea Ice

Sea ice is an important factor in global climate for numerous reasons:

It insulates the ocean from the cold atmosphere. The amount of sea ice cover influences heat and water to atmosphere and may affect local clouds and precip.
It has high albedo. This affects the amount of sunlight absorbed by the earth system.
The number of positive feedbacks associated with sea ice cause an amplification of climate change in the Arctic. Most important is the albedo feedback (warming causes less ice, less sunlight reflected back to space, enhanced warming).
It is important for human activities and biological habitats
- shipping, oil exploration
- arctic mammals (seals, polar bears) hunt, breed, and feed on the ice
Satellite observations show that Arctic sea ice concentrations have significantly decreased over the last 25 years. (rate of ~6%/decade for summer ice; 2002 had lowest summer ice cover on record)
Submarine observations also suggest that the Arctic ice pack has thinned dramatically (by about 1/3) in the last 20-30 years
It is unclear whether natural variability or climate change or a combination of the two are responsible for ice pack changes. Observational records are relatively short (20-30 yrs).
Climate simulations with increasing greenhouse gases show decreasing sea ice consistent with observations.
These models can give indications of how sea ice will change under different emission scenarios.
They can provide additional insight into what the consequences of sea ice changes will be for weather and climate, how this may affect biological habitats, etc.