Bering Strait Mooring Cruise 2004

R/V Alpha Helix

HX290 29th August - 6th September 2004 Nome - Nome

Rebecca Woodgate (UW), Sang Lee (UAF), Sarah Thornton (UAF),
Stephanie Moreland (UAF), Pieter deHart (UAF)
Lee Morrow (MATE Center, Monterey Peninsula College)

Corresponding author: Rebecca Woodgate woodgate@apl.washington.edu

ONR (N00014-99-1-0345)

NSF-SBI (OPP-0125082)

MAP
OVERVIEW
CRUISE REPORT
Warming of the Bering Strait inflow?
What is the Alaskan Coastal Current?
Cruise Images

During an 8-day physical and biogeochemical cruise to the Bering Strait and southern Chukchi Sea, three moorings (carrying current meters, temperature and salinity sensors, a nutrient sampler, a transmissometer and a fluorometer) deployed in the Bering Strait region for 1 year, were recovered and redeployed. Good weather also allowed completion of a CTD/ADCP survey of the region, with water sampling for nutrients, O-18 and hydrogen isotopes.

Highlights (see below) include:

- a warming and freshening of the Alaskan Coastal Current (here and here and here), between 2003 and 2004

- year-long timeseries of temperature, salinity and velocity in the Bering Strait (here)

- enough barnacles to sink a mooring? (here and here and especially here)

HX290 CRUISE REPORT

Appendix A - preliminary CTD sections
Appendix B - preliminary Mooring results
Appendix C - MODIS and Seawifs Images (courtesy of M.Schmidt)
Appendix D - O18 Bottle logs (hard copy only)
Appendix E - Instrument fouling from A2-03, A3-03 and A4-03
Appendix F - Mysterious white surface-trapped particles in the central Chukchi
Appendix G - Images of the freshwater front off Wales
Appendix H - Other cruise photographs

IS THE BERING STRAIT THROUGHFLOW WARMING?

Time-series from this cruise cover summer 2003 (left-hand-side of plots) and 2004 (right-hand-side of plots).

Cyan is at 40m depth at A4, in the Alaskan Coastal Current (see CTD section below).
This suggests warming (and freshening)
of the Alaskan Coastal Current.

Blue is at ca. 47m depth at A2 (top plot SBE, bottom plot RCM).
Red is at ca. 47m depth at A3 (top plot SBE, bottom plot RCM).
These do not suggest warming.

So, the surface waters are getting warmer.

(vertical scale = depth in m)

WHAT IS THE ALASKAN COASTAL CURRENT?

It's a warm, fresh current that hugs the eastern (U.S. coast) in the Bering Strait, as seen here on the right-hand-side of CTD sections of temperature and salinity taken on this cruise.

It has its origins in the freshwater outflow from the Yukon to the south of the Bering Strait and it continues northwards into the Chukchi Sea and finally the Arctic Ocean.

See how it sits as a surface wedge against the eastern side of the Bering Strait. Note that the mooring measurements illustrated above are at 40m and 47m depth and so only catch a small part of the large horizontal variability of this current!

Science Team for HX290
(photo by S. Thornton)

Mooring A303 safely back on board, covered in barnacles
(Spot the two red trifloats!)

For use of any of these figures, please contact
Rebecca Woodgate (woodgate@apl.washington.edu)

MODIS andSeaWiFS images kindly provided by the SeaWiFS Project,
NASA/Goddard Space Flight Center and Orbimage

Our thanks go to the crew of the Alpha Helix for their hard work, skill, professionalism, dedication and enthusiasm, and also to Mike Schmidt for providing us Seawifs images during the cruise.

We gratefully acknowledge financial support for this work from Office of Naval Research (ONR) High Latitude Dynamics Program and the National Science Foundation (NSF) Office of Polar Programs.

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