1. High Latitude Circulation
Global wind field - westerlies to easterlies
Drive subpolar & polar wind-driven gyres
Gyre patterns are broken up by land masses
Very different in northern/southern hemispheres
Intense heat losses & seasonal sea ice
Drive convection & deep water formation
Descending branch of the conveyor belt

2. Global Wind Field

3. Subpolar or Subarctic Gyres
Westerlies to easterlies give subpolar gyres
Easterlies
Low Dynamic Height
Upwelling
Divergence of Ekman Transports
Westerlies

4. Subpolar or Subarctic Gyres

5. Subpolar or Subarctic Gyres
High productivity in subpolar gyre
Less apparent in southern hemisphere

6. Global Wind Field

7. Polar Gyres Easterly winds around polar high give gyres EasterliesNP
Easterlies
High Dynamic Height
Downwelling
Convergence of
Ekman Transports

8. Arctic Ocean Distribution of land is important
Beaufort current is a polar gyre
Irminger & Labrador currents are subpolar gyres

9. Seasonal Sea Ice Formation
Microwave emission imagery from 78/79

10. Arctic Sea Ice is Thinning

11. Arctic Sea Ice is Thinning
Ice cover for Sept
2005
Red = typical Sept
Blue = typical Mar
Serreze et al. [2007]
Science
Sea-ice extent (bright white area) for September Median ice extents based on the period 1979 to 2000 for September (red line) and March (blue line)
illustrate the typical seasonal range.

12. Arctic Sea Ice is Thinning
Sept 2005
ig. 2. Time series of arctic sea-ice extent for alternate months and least-squares linear fit based on satellite-derived passive microwave data from November 1979 through November Listed trends include (in parentheses) the 95% confidence interval of the slope. Ice extent is also declining for the six months that are not shown, ranging from –2.8 ± 0.8% per decade in February to –7.2 ± 2.3% per decade in August.

13. Arctic Sea Ice is Thinning
Sept 2005
Fig. 3. Spatial pattern of the percent of IPCC AR4 model simulations (SRES A1B scenario) with at least 15% ice concentration for March (left) and September (right), averaged over the decade 2075 to For example, a value of 60% at a given location means that 60% of simulations predicted sea ice. Results are based on 11 models with realistic 20th-century September sea-ice extent.

14. Thinning of Arctic Sea Ice
Submarine obs
Compared 1958 to 1976 with 1994 to 1997
Draft of ice sheet

15. Thinning of Arctic Sea Ice
Unclear if this is a climate cycle or global warming signal

16. Arctic Circulation Arctic ocean remains mostly ice covered
Anti-cyclonic polar gyres are found (Beaufort current)
Much of the Eurasian Basin clears of sea ice each year
Changing in time - global warming??

17. Southern Ocean Circulation
Distribution of land is again important
Salinity is important
Strong Antarctic Circumpolar Current
CCW polar current
Localized fronts & gyres

18. Across Drake Passage
Temperature
Salinity

19. Seasonal Sea Ice Formation
Microwave emission imagery from 78/79

20. Antarctic Deep Waters - AAIW
WOCE hydrography
One time survey
1985 to 1997
Look at P18

21. P18 - Potential Temperature

22. P18 - Salinity

23. P18 – CFC-11 Concentrations

25. High Latitude Circulation
Global wind field - westerlies to easterlies
Drive subpolar & polar wind-driven gyres
Gyre patterns are broken up by land masses
Very different in northern/southern hemispheres
Intense heat losses & seasonal sea ice
Drive convection & deep water formation
Descending branches of the conveyor belt