THE NEAR-SURFACE LAYER OF THE OCEAN
surface. This effect influences the process of spring melting of the pack ice
as well as stimulating the spring algae bloom. The source of fresh water
(melting ice) is often localized within the relatively thin near-surface layer of
the ocean. In the Antarctic, for example, the typical thickness of the pack ice
is 1 m.
Pack ice adds dramatic variation to all atmosphere-ocean interactions
(McPhee, 1983; Muench, 1990; Gow and Tucker III, 1990). The classic
problem of air-sea interaction obtains a new dimension when air-sea-ice
interaction is considered. While the previous studies in polar seas (see
Muench, 1990 and McPhee, 1990 for reviews) have revealed fundamental
principles regarding the coupling of the ice cover, ocean, and atmosphere,
applying these principles to conditions at the pack ice edge is not simple.
The processes in the marginal ice zone are complicated by large spatial
gradients and by strong temporal variability. For example, field data from
the Greenland Sea (Buckley et al., 1979; Johannessen et al., 1983) show that
the marginal ice zone is an area of extreme upper ocean variability with
numerous fronts, upwelling or downwelling features, and eddies. In the
marginal ice zone, the ice concentration varies from 100% in the interior to
0% at the edge, with large fluctuations occurring over distances of a few
kilometers in both the across edge and along edge directions. Also, because
of the effect of incoming surface waves, average floe size in the marginal ice
zone changes from a few meters at the edge to thousands of meters at a
distance of 100 km to 200 km into the interior (Wadhams, 1973).
Though the marginal ice zone represents a small percentage of the total
ice cover in the polar region, its dynamical description is crucially important
in many processes associated with the pack ice variation. These include
(Brown, 1990): “…the growth, extent, and break up of the pack ice; the
regional ocean circulations and associated problems of the ocean mixedlayer dynamics, biology, and thermal structure; the dynamics of bottomwater formation in the marginal ice zone; the enhanced biological activity
with high phytoplankton concentration and large standing stock near the
marginal ice zone; and the mechanics of the long-time influence of the pack
ice and marginal ice zone on climatic and oceanic circulation.”
The upper ocean processes and ice mass changes that control the vertical
transfer of momentum, heat and salt between the ice and water are of
fundamental importance in controlling ice extent and motion in the marginal
ice zone. When the ice is blown over warm water, the underside melts; how
fast it melts depends on the rate of heat exchange in the ocean-ice boundary
layer (McPhee, 1990). At the same time, the transfer of heat, salt, and
momentum modifies the upper ocean and changes the physics of subsequent
ice and ocean interaction. When the upper surface ice is melted by radiative
and sensible heat input, the resultant mass flux also has an impact on upper
282
surface. This effect influences the process of spring melting of the pack ice
as well as stimulating the spring algae bloom. The source of fresh water
(melting ice) is often localized within the relatively thin near-surface layer of
the ocean. In the Antarctic, for example, the typical thickness of the pack ice
is 1 m.
Pack ice adds dramatic variation to all atmosphere-ocean interactions
(McPhee, 1983; Muench, 1990; Gow and Tucker III, 1990). The classic
problem of air-sea interaction obtains a new dimension when air-sea-ice
interaction is considered. While the previous studies in polar seas (see
Muench, 1990 and McPhee, 1990 for reviews) have revealed fundamental
principles regarding the coupling of the ice cover, ocean, and atmosphere,
applying these principles to conditions at the pack ice edge is not simple.
The processes in the marginal ice zone are complicated by large spatial
gradients and by strong temporal variability. For example, field data from
the Greenland Sea (Buckley et al., 1979; Johannessen et al., 1983) show that
the marginal ice zone is an area of extreme upper ocean variability with
numerous fronts, upwelling or downwelling features, and eddies. In the
marginal ice zone, the ice concentration varies from 100% in the interior to
0% at the edge, with large fluctuations occurring over distances of a few
kilometers in both the across edge and along edge directions. Also, because
of the effect of incoming surface waves, average floe size in the marginal ice
zone changes from a few meters at the edge to thousands of meters at a
distance of 100 km to 200 km into the interior (Wadhams, 1973).
Though the marginal ice zone represents a small percentage of the total
ice cover in the polar region, its dynamical description is crucially important
in many processes associated with the pack ice variation. These include
(Brown, 1990): “…the growth, extent, and break up of the pack ice; the
regional ocean circulations and associated problems of the ocean mixedlayer dynamics, biology, and thermal structure; the dynamics of bottomwater formation in the marginal ice zone; the enhanced biological activity
with high phytoplankton concentration and large standing stock near the
marginal ice zone; and the mechanics of the long-time influence of the pack
ice and marginal ice zone on climatic and oceanic circulation.”
The upper ocean processes and ice mass changes that control the vertical
transfer of momentum, heat and salt between the ice and water are of
fundamental importance in controlling ice extent and motion in the marginal
ice zone. When the ice is blown over warm water, the underside melts; how
fast it melts depends on the rate of heat exchange in the ocean-ice boundary
layer (McPhee, 1990). At the same time, the transfer of heat, salt, and
momentum modifies the upper ocean and changes the physics of subsequent
ice and ocean interaction. When the upper surface ice is melted by radiative
and sensible heat input, the resultant mass flux also has an impact on upper
282