Variability of Thermohaline Circulation and Freshwater Storage in the Arctic Ocean
Principal Investigator
Andrey Proshutinsky
Woods Hole Oceanographic
Woods Hole, MA 02543
Phone: 508-289-2796
FAX: 508-457-2181

Project Description
First Year Project Results
Publications and Talks
Digital Data Access

This research has been supported by a grant from NOAA. NOAA’s project manager:

John A. Calder, Director Arctic Research Office
NOAA Oceanic and Atmospheric Research R/AR
1315 East West Highway, Room 11362
Silver Spring, MD 20910
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.

  • 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?