1. Density of water increases as temperature decreases

2. Temperature (degrees Kelvin)

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

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

7. major surface currents (wind-driven)

8. velocity in cm/sec

15. Many large rivers drain freshwater into the Arctic Ocean

16. high latitude precipitation has been increasing

24. Retreat of North American (Laurentide) ice sheet

26. Sea ice

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

29. February ice pack

30. September ice pack