Density of water increases as temperature decreases

Temperature (degrees Kelvin)

Water masses of lower density float on top of those with higher density

Density of water increases as amount of dissolved salts increases (salinity)

major surface currents (wind-driven)

velocity in cm/sec

Many large rivers drain freshwater into the Arctic Ocean

high latitude precipitation has been increasing

Retreat of North American (Laurentide) ice sheet

Sea ice

Northern Hemisphere Polar Ice NASA/CSA Resources - Composite radar image draped on visible image Image source: NASA Jet Propulsion Lab

February ice pack

September ice pack