Polar seas Flashcards
what is the summer solstice
due to the Earths tilt on its axis the northern hemisphere is exposed to more sunlight creating a continuous day light in the summer, in the winter it is the opposite and the tilt is away from the sun
why are the polar regions so cold
1) the suns rays have to pass through more atmosphere
2) there is a low angular height of the sun in the summer
3) high albedo
4) long and dark winters
outline some characteristics of the artic ocean
1) small and shallow = 15.8 million km2
2) average depth =1200m
3) surrounded by land
4) wide and gentle continental shelf
what is the mean water temp of artic seas
-1.8dc
salt lowers the waters freezing temp
outline some characteristics of sea ice in the artic ocean
- not permanent, minimal in the summer before refreezing in the winter
- long term decline in ice cover
what is the artic tern
an artic bird species which migrates from pole to pole travelling 25,000 miles per year
- 30 yr life span
outline some characteristics of the antarctic (southern) ocean
1) larger and deeper than the artic= 20.3 million km2
2) average depth = 3200m
3) surrounds a continent
4) steep and narrow continental shelf
outline sea ice characteristics in the antartic/ southern ocean
- varies year to year
- increased 1% in last 10yrs
- loss of 4000Gt of ice 1994-2018
what is an ice shelf
ice formed on land which moved from the land to the ocean itself
what are the two ways the ice shelves can loose mass
1) carving of ice into chunks forming ice bergs
2) the underside of the ice melting
what are some characteristics of the Antarctic circumpolar current
- flows clockwise
- gives rise to antarctic convergence
- unimpeded
- upwellings of cold nutrient rich water
- worlds largest current
what is the antartctic divergence
an oceanic boundry between antartic water moving northwards meeting warmer sub antartic waters creating a mix
what is Ekman transport
occurs when ocean surface waters are influences by the friction force acting on them via the wind due to the coriolis effect therefore pushing water 90 degrees to the left
how does the Antarctic circumpolar current bring nutrient rich waters to the surface
- water pushing offshore creates a pressure gradient
- this drives more water back towards tge south
- these alternate forces pulling apart creates a geostrophic current which flows at greater depths (the ACC)
- this draws waters upwards from the depths
what is Antarctic bottom water
- produced at polynyas (extensive areas of ice free water within ice cover exposed to the cold wind)
- exposed areas are then frozen and salt left behind which sinks creating AABW = oxygen rich
