HR: 0830h
AN: OS21C-1138    [PDF]
TI: Freshwater content of the Beaufort Gyre: Observations from the Canada Basin in summer 2003
AU: * Proshutinsky, A
EM: aproshutinsky@whoi.edu
AU: Shimada, K
EM: shimadak@jamstec.go.jp
AU: McLaughlin, F
EM: mclaughlinf@pac.dfo-mpo.gc.ca
AU: Carmack, E
EM: CarmackE@pac.dfo-mpo.gc.ca
AU: van Hardenberg, B
EM: vanhardenbergb@pac.dfo-mpo.gc.ca
AB: The Canadian Basin of the Arctic Ocean contains approximately 45,000 km3 of fresh water, relative to a reference salinity of 34.80 (cf. Aagaard and Carmack, 1989) and is thus the major reservoir of fresh water stored in the Arctic Ocean. Its freshwater volume is 10-15 times larger than the total annual river runoff to the Arctic Ocean and at least twice that stored in sea ice. It follows that a release of only 5% of this freshwater would be sufficient to cause a salinity anomaly with the magnitude of the Great Salinity Anomaly observed in the North Atlantic in the 1970s. A substantial fraction of this freshwater storage is constrained by the dynamics of the anticyclonic Beaufort Gyre (BG), and is thus influenced by variability in wind forcing. Prior observations and models suggested that the freshwater content of the Canadian Basin had decreased by approximately 20,000 km3 during the later half of the 20th century. Here we will present an estimate of the freshwater content in the BG, based on observations collected during an international expedition (Canada, Japan, and USA) aboard the Canadian icebreaker CCGS Louis S. St-Laurent in the Canada Basin in summer 2003. We will also assess changes of BG water properties and sea ice conditions relative to climatology. Preliminary data show that, relative to the climatology: (a) the center of the BG is shifted toward Alaska; (b) there is a significant decrease of fresh water content in the intermediate layers of the BG; (c) the upper ocean (0-20 meters) is less saline; and (d) the concentration and thickness of sea ice is significantly less. We conclude that the amount of fresh water stored in the Canada Basin, which could be available for export to the North Atlantic, has decreased. On an interannual basis, recent positive trends in Arctic precipitation and river runoff may not compensate this freshwater loss by wind forcing. These facts should be taken into account in climate change assessments and scenarios.
DE: 4207 Arctic and Antarctic oceanography
DE: 4283 Water masses
DE: 4532 General circulation
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting