Interannual Changes in the Bering Strait Fluxes of Volume, Heat and Freshwater between 1991 and 2004

Rebecca A Woodgate, Knut Aagaard and Tom Weingartner

Published in Geophysical Research Letters, August 2006
Woodgate, R. A., K. Aagaard, and T. J. Weingartner (2006), Interannual changes in the Bering Strait fluxes of volume, heat and freshwater between 1991 and 2004, Geophys. Res. Lett., 33, L15609, doi:10.1029/2006GL026931.

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     Year-round moorings (1990 to 2004) illustrate interannual variability of Bering Strait volume, freshwater and heat fluxes, which affect many Arctic systems including sea-ice.  Fluxes are lowest in 2001 and increase to 2004.  Whilst 2004 freshwater and volume fluxes match previous maxima (1998), the 2004 heat flux is the highest recorded, partly due to ~ 0.5ºC warmer temperatures since 2002.  The Alaskan Coastal Current, contributing about 1/3rd of the heat and ¼ of the freshwater fluxes, also shows strong warming and freshening between 2002 and 2004.  The increased Bering Strait heat input between 2001 and 2004 (> 2x1020 J) could melt 640,000 km2 of 1 m thick ice; the 3-year freshwater increase (~ 800 km3) is about ¼ of annual Arctic river run-off.  Weaker southward winds likely explain the increased volume flux (~ 0.7 to ~ 1 Sv), causing ~ 80% of the freshwater and ~ 50% of the heat flux increases. 

© Polar Science Center, University of Washington, 2006

  For details, see paper
Map of Bering Strait with moorings Figure 1. The Bering Strait region, with mooring locations (dots) and NCEP wind grid points (crosses), showing sea surface temperature for 26th August 2004 (MODIS/Aqua level 1 image courtesy of Ocean Color Data Processing Archive, NASA/Goddard Space Flight Center). White areas indicate clouds.


    Figure 2. Thirty day smoothed time-series of near-bottom principal component (~ northward) of velocity (Vp), temperature (T), salinity (S) from the Bering Strait moorings. (A1-yellow; A2-cyan; A3-blue), with A4 (red) included in the T-S time-series.  Colors as per locations in Figure 1. Grey background is the climatological T-S from A3 [Woodgate et al., 2005b]. Line thickness indicates uncertainty in the means. 


Figure 3. Annual means (A1-yellow; A2-cyan; A3-blue; A4-red) of near-bottom principal component (~ northward) of velocity (Vp), temperature (T) and salinity (S) (top three panels); and estimates of transport, heat flux and freshwater flux (panels 3-6). For transport and flux estimates, blue (from A3) are for the entire strait and cyan (from A2) are only for the eastern channel. For transport, gray line is the entire strait transport as estimated from A2 only. Corrections for stratification and the ACC (not included) are ~ 1 - 2x1020 J/yr (heat) and 800 - 1000 km3/yr (freshwater). Dashed lines indicate estimated errors in the means. Grey dots in Vp indicate results from partial years (used for flux estimates). Bottom panel is annual mean NCEP wind at heading 330º, colors indicating location as per crosses in Figure 1.


© Polar Science Center, University of Washington, 2006

We gratefully acknowledge financial support for this work from  the Office of Naval Research (ONR) and the National Science Foundation (NSF)

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