Geoscience Reference
In-Depth Information
opened by shear stress and ice floe deformation, flows of cold polar
air induce very strong exchanges of sensible and latent heat. The
lower atmosphere is very unstable, which can lead to the development
of particularly thick atmospheric boundary layers if these free waters
extend over 100 km or more: for example, a 2 km thickness has been
measured in the Labrador Sea. The surface winds also tend to be
reinforced, leading to more waves and swell, which act on the
ice edges and contribute to their fracturing. When air flow comes from
the Arctic Ocean, next to eastern Greenland, the strong air-sea fluxes
are the cause of the density increase of the surface waters. Depending
on the initial haline stratification, they could possibly pull in the
waters beneath. In the Greenland Sea, deep convection movement can
be initiated, favored by the partial ice formation and the brine ejected
from this young ice. If the initial haline stratification is strong, due to
the presence of fresh surface waters, this deep convection process is
inhibited and the production of sea ice increases until an ice plate is
formed. However, the warming of the Arctic Ocean due to the
decrease of the ice coverage could lead to a reduction in the dense
water formation, indeed according to some authors, to a decrease in
the intensity of the North Atlantic Drift through a blockage in its
northward circulation.
The Antarctic region is also undergoing the effects of the Earth's
global warming, but with contrasting effects because of the presence
of the Antarctic continent. The seasonal ice fields seem to have grown
over the past few years, where the mechanism responsible for this is
not well understood. In summer, they disappear almost entirely, but a
melting of the coastal glaciers is also observed, which causes massive
influxes of fresh water into the sea.
Observation of sea ice:
- the installation of measuring stations
in situ
is a technical
challenge: outside of the perennial ice zones (at least those that survive
over several years), the risks due to ice plates colliding are high.
Moreover, because of the channel opening occurrence, floating
instrumentation is required, that must be resistant to freezing sea
spray. Finally, an additional, non-negligible risk is the material being
destroyed by a polar bear;
