3
Antarctic
Arctic
Ocean
Ocean
areal
30
14
sea ice, maximum
18(Oct.)
14 (March)
sea ice, minimum
2.5(March)
7 (Aug.)
area with seasonal ice 15.5
7
l)Antarctic Ocean: south of Polar Front; Arctic
Ocean: area of maximum ice cover.
Table 1. Area and distribution of
sea ice (106 km 2 ) in the Antarctic
and Arctic Oceans. Data from Jacka
(1981) and Walsh and Johnson (1979).
Total world ocean area is 361xl06
km2
ice and low sea temperatures, which range from about +5 0 at the Polar
Front to -1.80 in ice-filled waters.
In the Arctic Ocean the large-scale water transport is characterized
by an influx of Atlantic water west of Svalbard and to a lesser extent
in the Barents Sea. Influx through the Bering Strait may be only 1/3rd
of that from the Atlantic (Treshnikov and Baranov 1977). At the Polar
Front Atlantic water is submerged, but remains distinguishable for vast
areas at depths >100m. Outflow is mainly by the East Greenland and
Labrador currents. This water is cold and has a low salinity (29-340 /00)
due to ice melting as well as discharge from Siberian and North American
rivers. The ice of the central polar basin exhibits a slow anticyclonic
drift.
In the Antarctic Ocean the West Wind Drift is the dominating feature.
It is characterized by net upwelling, particularly at the Divergence, which separates the West Wind drift from the East Wind drift,
and a northern component of surface layer flow.
Downwelling prevails
at the Polar Front and close to the continent where bottom water is
formed, particularly in the Weddell Sea.
The continuous upwelling in the Atlantic Ocean results in the
highest nutrient concentrations found anywhere in surface waters. A
decrease is apparent during phytoplankton blooms, but complete exhaustion of surface nutrients is an unlikely event, at least in offshore
waters.
In contrast, Arctic surface waters exhibit maximum nutrient
values close to those of the North Atlantic and nutrient exhaustion
after a bloom. Table 2 shows that the minimum level for offshore Antarctic waters is actually higher than the maximum levels for the Arctic
ocean. Another notable difference is the 8-fold higher level of silicate compared to nitrate and phosphate in the Antarctic relative to the
Arctic Ocean. This is apparent also in the consumption pattern for
blooms (assuming the difference between maximum and minimum levels to
represent conversion into biomass), implying that bloom-forming diatoms
in the Antarctic are silicified to an extent far beyond Arctic diatoms.
The extreme seasonal variation in the light regime is revealed in
Fig. 2. The maxium sun height decreases with increasing latitude, for
Antarctic
Arctic
Ocean
Ocean
areal
30
14
sea ice, maximum
18(Oct.)
14 (March)
sea ice, minimum
2.5(March)
7 (Aug.)
area with seasonal ice 15.5
7
l)Antarctic Ocean: south of Polar Front; Arctic
Ocean: area of maximum ice cover.
Table 1. Area and distribution of
sea ice (106 km 2 ) in the Antarctic
and Arctic Oceans. Data from Jacka
(1981) and Walsh and Johnson (1979).
Total world ocean area is 361xl06
km2
ice and low sea temperatures, which range from about +5 0 at the Polar
Front to -1.80 in ice-filled waters.
In the Arctic Ocean the large-scale water transport is characterized
by an influx of Atlantic water west of Svalbard and to a lesser extent
in the Barents Sea. Influx through the Bering Strait may be only 1/3rd
of that from the Atlantic (Treshnikov and Baranov 1977). At the Polar
Front Atlantic water is submerged, but remains distinguishable for vast
areas at depths >100m. Outflow is mainly by the East Greenland and
Labrador currents. This water is cold and has a low salinity (29-340 /00)
due to ice melting as well as discharge from Siberian and North American
rivers. The ice of the central polar basin exhibits a slow anticyclonic
drift.
In the Antarctic Ocean the West Wind Drift is the dominating feature.
It is characterized by net upwelling, particularly at the Divergence, which separates the West Wind drift from the East Wind drift,
and a northern component of surface layer flow.
Downwelling prevails
at the Polar Front and close to the continent where bottom water is
formed, particularly in the Weddell Sea.
The continuous upwelling in the Atlantic Ocean results in the
highest nutrient concentrations found anywhere in surface waters. A
decrease is apparent during phytoplankton blooms, but complete exhaustion of surface nutrients is an unlikely event, at least in offshore
waters.
In contrast, Arctic surface waters exhibit maximum nutrient
values close to those of the North Atlantic and nutrient exhaustion
after a bloom. Table 2 shows that the minimum level for offshore Antarctic waters is actually higher than the maximum levels for the Arctic
ocean. Another notable difference is the 8-fold higher level of silicate compared to nitrate and phosphate in the Antarctic relative to the
Arctic Ocean. This is apparent also in the consumption pattern for
blooms (assuming the difference between maximum and minimum levels to
represent conversion into biomass), implying that bloom-forming diatoms
in the Antarctic are silicified to an extent far beyond Arctic diatoms.
The extreme seasonal variation in the light regime is revealed in
Fig. 2. The maxium sun height decreases with increasing latitude, for