Little Diomede Island, middle of the Bering Strait

BERING STRAIT: Pacific Gateway to the Arctic Rebecca Woodgate, Cecilia Peralta-Ferriz, Knut Aagaard University of Washington, USA  Tom Weingartner, Terry Whitledge University of Alaska, Fairbanks, USA Igor Lavrenov Arctic and Antarctic Research Institute, Russia Corresponding author: Rebecca Woodgate (woodgate@uw.edu)

NSF-Polar Programs ONR High Latitude NOAA Arctic Research RUSALCA Back to High Latitude Dynamics

BERING STRAIT BASICS Bering Strait Basic Facts - WHY is the Bering Strait throughflow important? - WHAT are we doing? - WHAT are we learning? 2007-2009 International Polar Year in the Bering Strait A Decade in the Bering Strait Bering Strait Ice Flux Other Publications

RECENT PUBLICATIONS Pacific-to-Arctic oceanic nitrate fluxes: First Bering Strait overwinter nitrate time-series show winter replenishment and suggest decadal flux increase,  Woodgate, Peralta-Ferriz and Jensen, submitted Aug 2024 Arctic and sub-Arctic mechanisms explaining observed increasing northward flow through the Bering Strait and why models may be getting it wrong, Peralta-Ferriz and Woodgate, 2023 Warming and Freshening of the Pacific Inflow to the Arctic from 1990-2019 implying dramatic shoaling in Pacific Winter Water ventilation of the Arctic water column, Woodgate and Peralta-Ferriz, 2021 Freshening of the Pacific Inflow to the Arctic, Woodgate, 2020, ASOF presentation and paper in preparation Seasonality and forcing factors of the Alaskan Coastal Current in the Bering Strait from July 2011 to July 2012 Morris 2019 MSc Thesis Recent Change in the Bering Strait, report to ASOF 2018 meeting, Woodgate & Peralta-Ferriz 2018 Increases in the Pacific inflow to the Arctic from 1990 to 2015, and insights into seasonal trends and driving mechanisms from year-round Bering Strait mooring data Woodgate, 2018 Flow Patterns in the Eastern Chukchi Sea: 2010-2015. Stabeno, Kachel,Ladd, Woodgate, 2018 The dominant role of the East Siberian Sea in driving the oceanic flow through the Bering Strait - conclusions from GRACE ocean mass satellite data and in situ mooring observations between 2002 and 2016 Peralta-Ferrriz and Woodgate, 2017 Variability, trends, and predictability of seasonal sea ice retreat and advance in the Chukchi Sea Serreze, Crawford, Stroeve, Barrett, and Woodgate, 2016 25 years (1990-2015) of year-round measurements in the Bering Strait, Woodgate, 2015, PDF of Presentation for the Arctic Observing Network Meeting, Seattle, Nov 2015 A Synthesis of Year-round Interdisciplinary Mooring Measurements in the Bering Strait (1990-2014) and the RUSALCA years (2004-2011) Woodgate,Stafford and Prahl, Oceanography, 2015 Observed increase in Bering Strait oceanic fluxes from the Pacific to the Arctic from 2001 to 2011 and their impact on the Arctic Ocean water column Woodgate et al, 2012 Quantifying Sea-Ice Volume Flux using Moored Instrumentation in the Bering Strait Travers 2012 MSc Thesis A Synthesis of Exchanges Through The Main Oceanic Gateways to the Arctic Ocean Beszczynska-Moeller et al., Oceanography, 2011. The 2007 Bering Strait Oceanic Heat Flux and anomalous Arctic Sea-ice Retreat Woodgate et al, GRL, 2010   Interannual changes in the Bering Strait Fluxes of Volume, Heat and Freshwater between 1991 and 2004 Woodgate, et al, GRL, 2006 Some Controls on Flow and Salinity in Bering Strait Aagaard, et al, GRL, 2006 Monthly Temperature, Salinity and Transport Variability of the Bering Strait Throughflow. Woodgate, et al, GRL, 2005 Revising the Bering Strait Freshwater Flux to the Arctic Ocean. Woodgate & Aagaard, GRL, 2005 Technical Report - Correction of Teledyne Acoustic Doppler Current Profiler (ADCP) Bottom-Track Range Measurements for Instrument Pitch and Roll Woodgate and Holroyd, October 2011 Technical Report - Using A3 as a climate station for the Bering Strait Throughflow Woodgate et al, August 2007

RESEARCH EXPEDITIONS Norseman II 2023 (4th - 14th July 2023) Norseman II 2022 (8th-19th September) Norseman II 2021 (7th - 17th July) Norseman II 2020 (8th - 18th September) Norseman II 2019 (5th - 15th September) Norseman II 2018 (10th - 19th August) Norseman II 2017 (7th - 15th July) Norseman II 2016 (7th - 15th July) ** Bering Strait 2015 Live Cruise BLOG** Norseman II 2015 (1st - 9th July) Norseman II 2014 (30th June - 7th July) Norseman II 2013 (3rd - 10th July) Khromov 2012 (10th - 20th July) Khromov 2011 (12th - 23rd July) Khromov 2010 (31st July - 11th August) Khromov 2009 (23rd Aug - 2nd Sept) Lavrentiev 2008 (1st-10th Oct) Sever 2007 (27th Aug - 5th Sept) Sir Wilfrid Laurier 2006 (1st -  22nd July) Sir Wilfrid Laurier 2005 (8th - 22nd July) Alpha Helix 2004 (29th Aug - 6th Sept) Alpha Helix 2003 (30th Jun - 8th July) Alpha Helix 2002 (20th - 29th June) Alpha Helix 2001 (4th - 16th Sept) Alpha Helix 2000 (25th Aug - 7th Sept) DATA ACCESS GOTO DATA ARCHIVE

BERING STRAIT BASICS   - The only ocean gateway between the Pacific and Arctic, and ~85km wide, ~55m deep - Divided into 2 channels by the two Diomede Islands - Covered by sea-ice from ~January to April - ANNUAL mean flow northward, but can flow southward for a week or more - Water speeds highly variable, from ~2.5 knots (120 cm/s) northward to ~1 knot (50 cm/s) southward depending on local wind - flow driven (supposedly) by a pressure gradient between the Pacific and the Arctic oceans, opposed by the local winds - Water surface temperature freezing in winter, max around 12 deg C in summer - Annual mean flow ~0.8 Sv (800,000m3/s) (Right is a schematic of the flows in the region from Danielson and Weingartner, click on the image to enlarge it)

WHY IS THE BERING STRAIT THROUGHFLOW IMPORTANT? For the Chukchi Sea - primary source of nutrients for the Chukchi (one of the most biologically productive regions of the world oceans) - dominates the water properties of the Chukchi For the Arctic - primary source of nutrients for Arctic ecosystems - melts back sea-ice in summer, - provides cold waters in winter to stabilize the upper Arctic ocean (thus influencing ice thickness and upper ocean mixing) - provides ~40% of the freshwater input to the Arctic - water properties determine ventilation depth of the Arctic For the World Ocean - an important part of the global freshwater cycle - believed to influence the Atlantic overturning circulation Pacific waters can be traced through the Arctic and out through Fram Strait and the Canadian Archipelago

Sea-surface temperature for 26th August 2004  in  the Bering  Strait  region.  In the east, red indicates the warm Alaskan Coastal Current in  the  east. Black dots mark our mooring sites, A1, A2,  A3  and  A3' (black  dots).  White  areas indicate clouds. (MODIS/Aqua level 1 image courtesy of Ocean  Color Data  Processing Archive, NASA/Goddard Space Flight Center.)

WHAT ARE WE DOING? - measuring the long-term variability of volume and water properties in the Bering Strait region We measure temperature, salinity, water velocity and sometimes ice thickness and motion, nutrients, fluorescence, transmissivity with subsurface oceanographic moorings (similar to the picture on the left) In summer/autumn, we take oceanographic sections in the Strait and the southern Chukchi Sea (see cruise reports) Since 1990, moorings have been deployed with only a 1 year break. We place moorings to monitor flow through the western (A1) and eastern (A2) channels of Bering Strait.  The western channel is in the Russian EEZ, an area to which we have only had occasional access.  In other years the western channel has been monitored by a proxy site at A3.  Left: Schematic of a typical mooring. ULS = Upward-looking sonar to measure ice thickness Steel Float  and Trifloat = for buoyancy RCM9=Aanderaa Acoustic Current meter to measure water velocity and temperature SBE=Seabird sensor measuring temperature, salinity, fluorescence, transmissivity NAS=nutrient measuring instrument RT=Acoustic releases for recovering mooring

WHAT ARE WE LEARNING?

That Bering Strait flows vary from year to year .. and that the 2004 heat flux is the highest recorded since 1990. Changes in the Bering Strait Fluxes of Volume, Heat and Freshwater between 1991 and 2004 Woodgate, et al, submitted GRL, 2006 That Bering Strait provides ~40% of the freshwater input to the Arctic Ocean. Revising the Bering Strait Freshwater Flux to the Arctic Ocean. Woodgate & Aagaard, GRL, 2005 Quantifying the seasonal variability of the Bering Strait throughflow, with implications for significant seasonal variation in how the Pacific waters ventilate the Arctic.   Monthly Temperature, Salinity and Transport Variability of the Bering Strait Throughflow. Woodgate, Aagaard, Weingartner, GRL, 2005

A DECADE IN THE BERING STRAIT
(for data to 2003, click here)

Monthly mean temperature and salinity in Bering Strait during 1990-2000.  The western channel of the strait (mooring A1) lies in the Russian EEZ and has often not been accessible.  The northern site (mooring A3), which lies just east of the Russia-U.S. convention line, is influenced by the flows through both channels.  It therefore can serve as a partial surrogate for the western channel site.  Note the pronounced annual cycle in both temperature and salinity.  The average peak-to-peak amplitude of the salinity variation is about 1.5 psu and is driven by freezing, which expels salt into the water.  In addition to the annual cycle of temperature and salinity, there are important longer-term variations.  In particular, the record of salinity through the past decade shows that the Bering Strait inflow to the Arctic freshened about 1 psu during 1991-92 and then remained relatively fresh until 1999-2000, when about one-half of the earlier freshening effect was reversed.  The temperature of the inflow has also changed significantly during the past decade, with a dramatic long-term warming that peaked during 1996-97.  This was followed by rapid cooling, so that water as cold as observed in summer 2000 was last seen in 1990-91.

BERING STRAIT ICE FLUX A combination of ice thickness data (e.g. from Upward Looking Sonars) and ice motion (e.g. from Acoustic Doppler Current Meters) can yield estimates of ice flux. For 1990 to 1991, these data suggest a mean annual northward ice flux, even though the ice flux at the start of the season is southward.   a) Time series of the northward velocity of water at 25m depth (red) and ice (blue) show a very strong correlation between the ice and the water motion.   b) Timeseries of ice thickness (assuming thickness = 1.13 x keel depth) shows  - the thickening of ice over the winter - that in the early winter (i.e. before day 352) northflowing water carries no ice.   c) From this, we can estimate the northward transport of water (red) in 106 m3/s and ice (blue) in 105 m3/s, (assuming the strait has a width of 65km and a triangular cross-section of maximum depth 55m).   d) Cumulative transports of water (red) in 2x1012 m3 and ice (blue) in 1011 m3 show that the cumulative ice transport is southward for the first part of the winter,  even though the cumulative water transport is always northward.

CRUISE REPORTS
Bering Strait 2000  - RV Alpha Helix  - HX235
Bering Strait 2001  - RV Alpha Helix  - HX250
Bering Strait 2002  - RV Alpha Helix  - HX260
Bering Strait 2003  - RV Alpha Helix  - HX274
Bering Strait 2004  - RV Alpha Helix  - HX290
Bering Strait 2005 - CCGS Sir Wilfrid Laurier - SWL2005

REFEREED PUBLICATIONS (back to top)

Woodgate, R.A.,  K. Aagaard, and T.J. Weingartner, Monthly temperature, salinity, and transport variability of the Bering Strait throughflow. Geophys. Res. Lett., Vol. 32, No. 4, L04601 10.1029/2004GL021880, 2005

Woodgate, R. A., and K. Aagaard, Revising the Bering Strait freshwater flux into the Arctic Ocean, Geophys. Res. Lett., 32, L02602, doi:10.1029/2004GL021747, 2005
 
Walsh, J.J., D.A. Dieterle, F.E. Muller-Karger, K. Aagaard, A.T. Roach, T.E.  Whitledge, and D. Stockwell, CO2 cycling in the coastal ocean. II. Seasonal organic loading of the Arctic Ocean from source waters in the Bering Sea, Continental Shelf Res., 17,1-36, 1997.

Roach, A.T., K. Aagaard, C. H. Pease, S.A. Salo, T. Weingartner, V. Pavlov, and M. Kulakov, Direct measurements of transport and water properties  through Bering Strait, J. Geophys. Res., 100, 18,443-18,457, 1995.

Coachman, L.K., and K. Aagaard, Transports through Bering Strait: Annual and interannual variability, J. Geophys. Res., 93, 15535-15539, 1988.

Aagaard, K., A.T. Roach, and J.D. Schumacher, On the wind-driven variability of the flow through Bering Strait, J. Geophys. Res., 90, 7213-7221, 1985.

Schumacher, J.D., K. Aagaard, C.H. Pease, and R.B. Tripp, Effects of a shelf  polynya on flow and water properties in the northern Bering Sea, J. Geophys. Res., 88, 2723-2732, 1983.

Coachman, L.K., and K. Aagaard, Re-evaluation of water transports in the vicinity of Bering Strait, in The Eastern Bering Sea Shelf: Oceanography and Resources, vol. 1, edited by D.W. Hood and J.A. Calder, pp. 95-110, National Oceanic and Atmospheric Administration, Washington, D.C., 1981.

Coachman, L.K., K. Aagaard, and R.B. Tripp, Bering Strait: The Regional  Physical Oceanography, 172 pp., University of Washington Press, Seattle, 1975.

Coachman, L.K., and K. Aagaard, On the water exchange through Bering Strait, Limnol. Oceanogr., 11, 44-59, 1966.

For use of any of these figures, please contact Rebecca Woodgate (woodgate@apl.washington.edu)
© Polar Science Center, University of Washington, 2004

We gratefully acknowledge financial support for this work from  the Office of Naval Research (ONR), High Latitude Dynamics program, the National Science Foundation (NSF), and the National Oceanic and Atmospheric Administration (NOAA).
 
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