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Beaufort Gyre Freshwater Observing System

OCCI Project Funded: 2004

This project investigates basin-scale mechanisms regulating freshwater content in the Arctic Ocean and particularly in the Beaufort Gyre (BG).  The major hypothesis of the project is that the BG accumulates a significant amount of freshwater from different sources under anticyclonic (clockwise) wind forcing, and then releases this freshwater when this forcing weakens or changes direction to a cyclonic (counterclockwise) rotation.  This accumulation and release mechanism could be responsible for the observed salinity anomalies in the North Atlantic and for a decadal scale variability of the Arctic system, as the BG may both filter annual river inputs and pulse freshwater outflows. 

One of the major goals of this project was to monitor long-term variability of freshwater and heat content in this climatically sensitive region of the Arctic Ocean by establishing the Beaufort Gyre Observing System (BGOS) and redeploying three moorings (first deployed for one year in 2003 under a grant from the NSF Office of Polar Programs).

The Beaufort Gyre has been characterized in the past as the region of “relative inaccessibility,” because of the difficulty of reaching it by icebreaker (due to heavy ice conditions) and by airplane (due to its remoteness from the mainland).  As a result, this area is one of the most poorly sampled regions in the Arctic Ocean. 

In 2002, NSF’s Office of Polar Programs recognized the great importance of the BG in the freshwater balance of the Arctic Ocean and funded the proposal, “Beaufort Gyre Freshwater Experiment:  Study of Freshwater Accumulation and Release Mechanism and a Role of Freshwater in Arctic Climate Variability.”  As part of the field experiment for the NSF-funded project, in 2003 we deployed:  three moorings with McLane Moored Profilers (MMPs) (to measure Conductivity-Temperature-Depth [CTD] and velocity); upward-looking sonars for ice draft measurements; bottom pressure recorders; and, four expendable surface buoys with CTDs.

 However, given the importance of this region for Arctic climate studies, we endeavored to investigate interannual and longer variability.  Thus, it was necessary to continue acquiring the same data for several years, even though the observational program supported by NSF ended in 2004.

However, given the importance of this region for Arctic climate studies, we endeavored to investigate interannual and longer variability.  Thus, it was necessary to continue acquiring the same data for several years, even though the observational program supported by NSF ended in 2004.

The current project funded by WHOI’s Ocean and Climate Change Institute allowed us to continue data collection in 2004 by providing support for equipment and operations in 2004 and mooring recovery in 2005, while a proposal to NSF was prepared to establish a long-term observational program in the Beaufort Gyre.  In 2004, we used funds from the Comer Science and Education Foundation to purchase new mooring wire and supplies to refurbish the scientific instruments and partially support the costs to carry out our August-September 2004 expedition to the Beaufort Gyre on the Canadian Coast Guard Icebreaker Louis S. St. Laurent

The times and locations of the recovery and deployment operations during the cruise in 2004 are given in Table 1.

Mooring Designation

Water Depth, m

2003 Location

2004 Recovery

2004 Deployment

2004 Location

BGFE-A

3824

    75° 00.39'N; 149° 58.752'W

10-Aug

12-Aug

75° 00.242' N      149° 57.742'W

BGFE-B

3821

78° 01.491'N     149° 49.378'W

15-Aug

17-Aug

78° 00.967'N      149° 51.544'W

BGFE-C

3722

76° 59.254'N    139° 54.229'W

20-Aug

22-Aug

76° 59.457'N      139° 58.407'W

ITP & IMB

19-Aug

77° 10.4'N          141° 13.0'W


Four moorings were deployed in August 2004 in the Beaufort Gyre region.  Three moorings (Figure 2) held profiling equipment under the ice.  We also deployed two Arctic drifting buoy systems in the sea ice.  One buoy is an Ice Mass Balance (IMB) buoy developed at the US Army Cold Regions Research and Engineering Laboratory in Hanover, New Hampshire, and the other is an Ice-Tethered Profiler (ITP) developed at WHOI.  The IMB measures properties of the surface atmosphere and ice floe in which it is situated, using an air temperature monitor, barometric pressure sensor, ice thermistor strings, a snow depth sensor, and an upward looking sonar.  Primarily, the IMB is designed to monitor the growth and ablation of sea ice.  The ITP is designed to autonomously acquire profiles of the temperature and salinity of the upper ocean from 10 to 800 meters for several years, to understand the state and variability of the upper Arctic Ocean under sea ice through all seasons.  Both the IMB and ITP transmit their data (and locations) back to their respective laboratories via satellites.  For this experiment, one of each buoy type were deployed together on the same ice floe to obtain concurrent data while drifting with the sea ice around the Beaufort Gyre.  For more information on this project see our Web site at: http://www.whoi.edu/beaufortgyre/dispatch2004/index2004.html

In September 2004, NSF granted our 5-year proposal, “The Beaufort Gyre System:  Flywheel of the Arctic Climate?”  Now, all the moorings to be recovered in 2005 with support of the WHOI Ocean and Climate Change Institute will be maintained until 2008 with NSF support, and the investigation of the BG system will continue uninterrupted. 

Originally published: January 1, 2004