The 2007 Bering Strait Oceanic Heat Flux and anomalous Arctic Sea-ice Retreat

Rebecca A Woodgate, Tom Weingartner, and Ron Lindsay

Published in Geophysical Research Letters, January 2010
Woodgate, R. A., T. Weingartner, and R. Lindsay (2010), The 2007 Bering Strait oceanic heat flux and anomalous Arctic sea-ice retreat,
Geophys. Res. Lett., 37, L01602, doi:10.1029/2009GL041621.

Paper (downloadable as pdf)

Please contact Rebecca Woodgate ( for use of any of this material

   To illuminate the role of Pacific Waters in the 2007 Arctic sea-ice retreat, we use observational data to estimate Bering Strait volume and heat transports from 1991 to 2007. In 2007, both annual mean transport and temperatures are at record-length highs. Heat fluxes increase from 2001 to a 2007 maximum, 5-6x1020J/yr. This is twice the 2001 heat flux, comparable to the annual shortwave radiative flux into the Chukchi Sea, and enough to melt 1/3rd of the 2007 seasonal Arctic sea-ice loss. We suggest the Bering Strait inflow influences sea-ice by providing a trigger for the onset of solar-driven melt, a conduit for oceanic heat into the Arctic, and (due to long transit times) a subsurface heat source within the Arctic in winter. The substantial interannual variability reflects temperature and transport changes, the latter (especially recently) being significantly affected by variability (> 0.2Sv equivalent) in the Pacific-Arctic pressure-head driving the flow.

© Polar Science Center, University of Washington, 2009

  For details, see paper
SST and IceEdge Maps of Bering Strait region

Figure 1:
(a) Bering Strait summer MODIS Sea Surface Temperature (SST), marking moorings (black dots) and NCEP wind points (x, colors as per Figure 2f).
(b) Chukchi Sea AMSR-E sea-ice concentration, with schematic topography. White arrows mark the three main water pathways via HV,
Herald Valley; CC, Central Channel; and BC, Barrow Canyon. Black box marks region of (a).

Figure 2: Bering Strait time-series from 1991-2007. Uncertainties are ~ 0.1Sv, 0.8x1020J/yr. See text for possible systematic errors.
Volume transport, from A3 data alone – grey, hourly; blue, 30-day smoothed.
Annual mean (AM) transports (not including the Alaskan Coastal Current (ACC), ~ 0.1 Sv) – blue, total from A3; dashed cyan, total from A2; solid cyan, eastern channel transport only from A2.
Temperatures – blue, 30-day smoothed A3 near-bottom; red, 7-day average AVHRR-SST.
AM temperature– blue, A3 near-bottom; cyan, A2 near-bottom; red, SST near A3.
AM heat fluxes – cyan, from A2 for eastern channel only; blue, total from A3 data only; red area, total including ACC correction (~ 1x1020J/yr) and a 10m (lower bound) or 20m (upper bound) surface layer. Black crosses, amount of heat added by a 20m surface layer.
Transport attributable to AM NCEP wind (heading 330º, i.e., ~ northwestward) - black, average over 4 nearest points (marked on Figure 1a) i.e., blue and red, ~150km north of the strait (67.5ºN,170ºW and 167.5ºW); yellow and cyan, ~ 100km south of the strait (65ºN, 170ºW and 167.5ºW).
Transport attributable to the pressure-head term from annual fits – green, weekly data; black, annual mean.
       Tiime series of Bering Strait data

Transport, temperature and heat flux by month

Figure 3:
For extreme heat flux years (rows – lows: 2001, 2005; highs: 2004, 2007), 30-day smoothed A3-transports (left column), temperatures (middle column) and heat flux (right column), compared to the entire data set from 1991-2007 (grey). Last row: Cumulative sums of the above, colors indicating year as per upper panels.

© Polar Science Center, University of Washington, 2009

We gratefully acknowledge financial support for this work from  the National Science Foundation (ARC-0632154 and ARC-053026) with shiptime from NOAA-RUSALCA.

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