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
Citation:
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.

Abstract
Paper (downloadable as pdf)
Figures

Please contact Rebecca Woodgate (woodgate@apl.washington.edu) for use of any of this material

Abstract  
   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

Figures
  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.
(a)
Volume transport, from A3 data alone – grey, hourly; blue, 30-day smoothed.
(b)
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.
(c)
Temperatures – blue, 30-day smoothed A3 near-bottom; red, 7-day average AVHRR-SST.
(d)
AM temperature– blue, A3 near-bottom; cyan, A2 near-bottom; red, SST near A3.
(e)
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.
(f)
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).
(g)
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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