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Project Description
Problem Formulation
The present state of the Arctic Ocean and
its influence on the global climate system strongly depend
on the Arctic Ocean freshwater budget (Aagaard and
Carmack, 1989, hereinafter A&C) because fluctuations in
the freshwater export can significantly influence
the depth and volume of deep water formation in the North
Atlantic (NA) and ultimately the strength of the
global thermohaline circulation.
The traditional approach
for investigations of the freshwater budget of
the Arctic Ocean has been to perform a detailed analysis of
its major components including river runoff, the
inflow of waters from the Atlantic and Pacific Oceans, the
outflows through Fram Strait and the Canadian Archipelago,
the atmospheric moisture flux and the annual
cycle of ice formation and melt (see Lewis [2000]).
Significantly less attention has been paid to the
processes involved in the storage of FW in the Arctic
Ocean and its temporal variability.
The regional differences in this storage (e.g., in sea ice
thickness and in ocean salinity)
are substantial (A&C; Steele et al., 1996). For
instance, the Canadian Basin of the
Arctic Ocean contains about 45,000 km3 of fresh water
(calculated relative to the
salinity 34.80 by A&C). This is 10-15 times larger than
the total annual river
runoff to the Arctic Ocean, and at least two times larger
than the amount of fresh
water (FW) stored in the sea ice. A release of only 5% of
this FW is enough to cause
a salinity anomaly in the North Atlantic comparable in
magnitude to the Great Salinity
Anomaly of the 1970s. The largest of the anomalies is
located in the Beaufort Gyre (BG),
identified by a salinity minimum at depths 5-400 m
(Figure 1A-C (pdf).). This anomaly drives the
BG geostrophic circulation anticyclonically (Figure 1D (pdf)).
We propose that the freshwater
budget of the BG and the freshwater flux to the NA
depend significantly on the intensity
of this salinity anomaly and climatic conditions
conducive to the transport
of FW from the BG to the NA.
Goal and Objectives
The major goal of this project is to investigate the variability
of the thermohaline circulation and freshwater storage in the Arctic
Basin under the influence of different climate regimes based on analysis
of existing data and numerical modeling.
Objectives
- Determine and document the variability of fresh water storage and
thermohaline circulation of the Arctic Ocean;
- Identify the ocean response (freshwater storage and thermohaline
circulation) to the seasonal, interannual and the apparent
10-15-year cycle of atmospheric circulation modes
(Proshutinsky and Johnson, 1997) in the Arctic.
Scientific Questions
- What is the mechanism for accumulation of
fresh water in the center of the Beaufort Gyre?
- Is this fresh water transported to the North
Atlantic and what are the conditions that
influence its rate of transport?
- What is the primary driver of the
Arctic Ocean circulation, thermohaline
or wind-driven forcing?
- How does the wind-driven circulation
change the thermohaline structure and resultant
circulation seasonally, annually, and decadally?
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