Geoscience Reference
In-Depth Information
cover areas implies a decrease of reflection and an increase of energy absorption resulting
in more ice-snow melting. Vice versa, when the ice-snow cover increases, this leads to in-
creased reflection, supporting further snow cover and ice generation. Changes in ice cover
within the Arctic Basin may also be related to ocean circulation. Part of the inflowing wa-
ter of Atlantic origin can penetrate further north into the Arctic Basin at the Eurasian side,
forming there an intermediate and deep water layer. Studies of historical data of this water
mass, extending over one hundred years, show that since the 1970s this water has warmed
It was likewise confirmed that while moving anticlockwise around the basin, the water of
Atlantic origin cooled. Taken together these findings suggest an increase of the heat flux
from the layer with Atlantic water to the sea ice, leading to a thinning of the ice. This pro-
cess could have preconditioned the ice cover for the dramatic decrease observed during the
IntheGreenland,Iceland,andNorwegianseasthesurfacelayerdensityisstronglyde-
pendent upon the salinity, which varies with the inflow of relatively high saline water from
the south and inflow of low-salinity melt water from the Arctic Basin. High salinity com-
bined with cooling, strong winds and evaporation in the winter season, together drive the
vertical circulation, convection, and deep water formation in the northern North Atlantic;
particularly in the Greenland Sea. However, the rate of renewal of the interior deep waters
also depends upon the mixing in the interior of the ocean. There will always be some mix-
ing due to the energy supplied by the tidal motion. The energy input from the wind, com-
bined with other air-sea interaction processes, including breaking wind-generated waves,
generates mixing in the top several hundred metres. The wave processes have a noticeable
influence on the exchange of oxygen between the atmosphere and the ocean.
Time-series of observations during 1950-2000 of the atmospheric pressure difference
between the Icelandic low and the Azores high, measured between Iceland and Lisbon (the
NAO), the Gulf Stream intensity, and the water temperature in the Labrador Sea, show
decadal variability in all (Latif and Meincke,
2001
).The NAOindicates an increasing trend
since the 1960s, the water temperature in the Labrador Sea shows a decreasing trend since
