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

Global Wind Field

Subpolar or Subarctic Gyres

• Westerlies to easterlies give subpolar

gyresEasterlies

Westerlies

Divergence of Ekman Transports

Upwelling

Low Dynamic Height

Subpolar or Subarctic Gyres

Subpolar or Subarctic Gyres

• High productivity

in subpolar gyre

• Less apparent in

southern

hemisphere

Global Wind Field

Polar Gyres• Easterly winds around polar high give gyres

East

erlie

s

Convergence of Ekman Transports

Downwelling

High Dynamic Height

NP

Arctic Ocean

• Distribution of land

is important

• Beaufort current is

a polar gyre

• Irminger & Labrador

currents are

subpolar gyres

Seasonal Sea Ice Formation

Microwave emission imagery from 78/79

Arctic Sea Ice is Thinning

Arctic Sea Ice is Thinning

Ice cover for Sept 2005

Red = typical SeptBlue = typical Mar

Serreze et al. [2007] Science

Arctic Sea Ice is Thinning

Sept 2005

Arctic Sea Ice is Thinning

Sept 2005

Thinning of Arctic Sea

Ice • Submarine obs

• Compared 1958

to 1976 with

1994 to 1997

• Draft of ice sheet

Thinning of Arctic Sea Ice

Unclear if this is a climate cycle or global

warming signal

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??

Southern Ocean

Circulation• Distribution of land is

again important

• Salinity is important

• Strong Antarctic

Circumpolar Current

• CCW polar current

• Localized fronts &

gyres

Across Drake Passage

Temperature Salinity

Seasonal Sea Ice Formation

Microwave emission imagery from 78/79

Antarctic Deep Waters -

AAIW

• WOCE

hydrography

• One time survey

• 1985 to 1997

• Look at P18

P18 - Potential Temperature

P18 - Salinity

P18 – CFC-11 Concentrations

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