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
|
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. |
|
|
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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