HR: 14:35h
AN: GC43A-03 INVITED     [Abstracts]
TI: SubArctic Oceans and Global Climate
AU: * Rhines, P B
EM: rhines@ocean.washington.edu
AF: University of Washington, School of Oceanography Box 357940, Seattle, WA 98195 United States
AB: The passages connecting the Arctic Ocean with the Atlantic and Pacific, and their `mediterranean' basins, are focal points for the global meridional overturning circulation, and all of the climate impacts which this implies. It is also a difficult region to model accurately: the sensitivity of climate models to subpolar ocean dynamics is well-known. In this talk we stress the need to instrument and analyze the subpolar oceans, and some examples of sustained observations developing there. Results from satellite altimetry, recent Seaglider deployments from Greenland, and mooring arrays will be described. In particular we show the first Seaglider sections of hydrography and bio-optical profiles of the Labrador Sea (one of the first extended deployments of this autonomous undersea vehicle); we discuss the decline during the 1990s of the subpolar gyre circulation of the Atlantic from its great strength during the positive NAO period of the early 1990s, and its relevance to the salinity decline observed over a much longer period; we review observations of the flows at the Iceland-Scotland Ridge and Davis Strait, argued in terms of volume transport plots on the potential temperature/salinity plane; we display maps of the `convection resistance' (related to dynamic height) and its sensitivity to surface low-salinity water masses and their partition between shallow continental shelves and deep ocean. This is a particularly exciting time for climate studies, with fundamental properties of the atmosphere-ocean circulation under debate, even before one considers natural and human-induced variability. Is the four-decade long decline in subArctic salinity the result of increased hydrologic cycle, increased or altered Arctic outflow to the Atlantic, or slowing of the subpolar circulation? Is the basic intensity of the MOC more dependent on high-latitude buoyancy forcing, or wind- or tide-driven mixing in the upwelling branch, or possibly wind-stress at high latitude? Is the uptake of anthropogenic carbon from the atmosphere sensitive to changes in the gyre circulations and MOC? How does the oceanic circulation participate in the remarkably `tall' subArctic/Arctic climate system, that reaches up through the atmospheric storm tracks to the stratosphere? These questions are tied closely to the Arctic Basin itself, where thermodynamic warming competes with wind-induced anomalies and trends in sea-ice cover. The Arctic-SubArctic Ocean Flux (ASOF) program aims to narrow the uncertainty implicit in these questions, constructing a bridge between Arctic Ocean circulation dynamics and the dynamics of the subtropical Atlantic and Pacific. By defining a series of both flux array measurements and process studies, ASOF can illuminate what has long been {\it aqua et glacies incognita.}
UR: http://www.ocean.washington.edu/research/gfd/gfd.html
DE: 4207 Arctic and Antarctic oceanography
DE: 4283 Water masses
DE: 1620 Climate dynamics (3309)
DE: 1635 Oceans (4203)
SC: Global Climate Change [GC]
MN: 2004 AGU Fall Meeting