AS 91413
Year 13 SCIENCE
Ocean systems – course topics
1. Ocean composition
2. Ocean circulation
3. The carbon cycle
4. Transport matter, energy – heat, tides and waves
5. Southern Oscillation – El Nino & La Nina
Ocean systems – course topics
 1.
Ocean composition – temperature, density, salinity,
pressure and gradients
 2.
Ocean circulation – currents, thermohaline circulations,
Coriolis effect
 3.
The carbon cycle – physical pumps, biological pumps,
carbonate and CO2 chemistry
 4.
Transport matter, energy – heat, tides , waves and
Tsunamis
 5.
Southern Oscillation – El Nino & La Nina
In the plot, one can discern three layers:
Halocline -arctic
The halocline is a
150m deep band of
water starting at 50m
depth of steeply rising
salinity
Three layers:
Mixed top layer of
 The top 50m mixed layer has low salinity < 33 PPT
 Originates from inflow of freshwater of melting
glaciers and terrestrial rivers in Siberia, Alaska &
Canada during summer
 The temperature is -1.8 °C, which is very near to the
freezing point, chilled by cold air.
 This top layer blocks heat transfer from the warmer,
water below from the Gulf stream into the ice sheet
 This insulation has considerable effect on the
thickness of the ice.
Arctic & Antarctic Haloclines
 In high latitudes of the Arctic Ocean, Bering sea and
the Southern Ocean, the surface waters are actually
colder than the deep waters.
 Here the halocline is responsible for maintaining
water column stability- isolating the surface waters
from the deep waters. I
 n these regions, the halocline is important in allowing
for the formation of sea ice
Arctic ice cap at North Pole
Dark blue areas cold
water -1.8 to 1 C
Pale blue ice melt, floes,
ice bergs
White Sea ice
Arctic ice cap at North Pole
Dark blue areas cold
water -1.8 to 1 C
Pale blue ice melt, floes,
ice bergs
White Sea ice
Nuclear submarine & polar bears
Ice formation in winter
 As ice forms from sea water the salts are left behind in
the water.
 The ice is fresh
 As a result the salinity increases , becoming more
dense an falling to greater depths.
Summary
 Warm water heated by the sun lies near tropical and
equatorial oceans close to the ocean surface and is less
dense
 Cold water lies near the poles away from direct sun
and is deeper down
 Thermocline is the rapid change in temperature with
depth which is found in the pycnocline layer.
 Large currents move around the world mixing cold
water with warm with many effects on climate, and
plankton, plants and animals living in the sea.
Cross – section through the ice cap
Bering
Strait
Polar Ice cap
Arctic Halocline is 50-200m thick
50-200m