GEOS 110 FALL 2011

SEA ICE

Polynyas – openings in the ice

• Persistent, forming year after year

• 2 types: Sensible & Katabatic

Polynyas – openings in the iceKatabatic – Dense Drainage Winds

Understanding and Projecting the Changes in the Oceanic Conveyor Belt is a Critical Question for

Science

The North Atlantic Current provides about 60% of the inflow to the Arctic Ocean bringing warmer water from the Atlantic Ocean. Some water also moves into the Arctic Ocean from the Bering Sea and the Pacific Ocean, by way of the Bering Strait.

Water flows from the Arctic Ocean into the Pacific and Atlantic Oceans, as well as into a number of surrounding seas. By far, the greatest volume of water leaves the Arctic Ocean through the passage between Greenland and Spitsbergen.

Arctic inflow Arctic outflow

Minimum arctic sea-ice extent from 1979 to 2007

observations vs. models

observed sea ice decline is 50 years ahead of expectation frommodels forced by GHG’s (and other human and natural radiativeforcings discussed earlier) suggesting models do not capture allrelevant interactions

IPCC FARmodelensemble

mean ofall models

“A linear increase in heat in the Arctic willlead to a non-linear, and accelerating,loss of ice”

impacts of an summer-ice free Arctic ?

• sharply warmer Arctic Autumn andWinter from increased O-A heat fluxes(polar amplification of warming)

• local ecological and human impacts

• altered weather patterns outside theArctic (due to altered patterns of heatingand pressure)

• altered salinity and ocean circulation

no evidence of summer-ice free Arctic inlast million years