150o W
120
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90
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120 oE
150 oE
180oW
70oN
75oN
80oN
85oN
Mendeleev Ridge
ChukchiBorderland
The Arctic CrossroadsThe Influence of the Mendeleev Ridge and the
Chukchi Borderland on the Large-scale Circulation ofthe Arctic Ocean
Rebecca Woodgate and Knut Aagaard, University of WashingtonJim Swift, Scripps Institution of Oceanography
Bill Smethie, Lamont-Doherty Earth ObservatoryKelly Falkner, Oregon State University
Ed Carmack and Fiona McLaughlin, Institute of Ocean Sciences, B.C.
Rebecca A Woodgate, M.A., D.Phil.Research Assistant Professor
Applied Physics Laboratory/School of OceanographyUniversity of Washington, Seattle
Dr Rebecca Woodgate
B.A. Hons (First Class) and M.A.Physics and Theoretical PhysicsUniversity of Cambridge, United Kingdom
D.Phil. Physical OceanographyUniversity of Oxford, United Kingdom- researching use of satellite data to improvecomputer models of ocean circulation
Post-doctoral StudiesAlfred-Wegener-Institute of Polar and MarineResearch, Bremerhaven, Germany- Arctic and Antarctic physical oceanographicresearch, especially the Greenland Sea, theFram Strait and the Weddell Sea- ship-based observations in collaboration withGermany, Norway, U.S.A. and U.K.
Current Research CareerResearch Assistant ProfessorApplied Physics Laboratory/Department of OceanographyUniversity of Washington, Seattle, U.S.A.- Arctic physical oceanographic research- observational projects in the high Arctic, at the North Pole, in the ChukchiSea and in the Bering Strait- teaching of physical oceanography to University of Washington under-graduate students
Motivation- an understanding of the physical Arctic system, from large-scale circula-tion to regional oceanography, the processes and implications of climate
change in the Arctic and its feedback into World Ocean circulation(http://psc.apl.washington.edu/HLD)
135o W
90
o W
45 oW
0o
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90
o E
135 oE
180oW
70oN
80oN
Mendeleev Ridge
ChukchiBorderland
Lomonosov Ridge
Atlantic waters Pacific waters
Transfer out into the deep basin?
Barrow
Large-Scale Arctic Ocean Circulation
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E
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1. A boundary current, followingthe depth contours, carries
warm Atlantic waters into theChukchi Borderland region
3. Some of the boundary cur-rent, and some of the Pacificwaters are diverted into the
deep Arctic Ocean
2. The nutrient-richPacific waters enter theArctic via the Chukchi
Sea.
The fate of the Atlantic and Pacific waters is determined bythe interplay of topography, wind, currents and ice motion
in the region of the Chukchi Borderland
4. Some of the boundarycurrent and some of thePacific waters continuealong the north coast of
Alaska
Mendeleev Ridge
ChukchiBorderland
The Role of the Arctic Crossroads
Barrow
Why do we care?
150o W
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o W
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Mendeleev Ridge
ChukchiBorderland
Barrow
1. The “warm” Atlanticlayer carries heat. Itsfate can influence ice
thickness.
2. The Pacific waters carry nutrients.The fate of these waters in the Arcticcan affect the biological productivity.
3. The interplay of Atlantic andPacific waters may be affected bythe changes in Arctic oceanic and
atmospheric circulation we seeover the last decade (or longer).
4. A better understanding of theArctic Ocean Boundary Current
and the interaction of Atlantic andPacific waters in this region will
improve computer models of Arc-tic circulation and Arctic climate
change.
How can the Atlantic waters affect theice?
Temperature SalinityDepth
ca.50m
ca.300m
ca.200m
Warm (0 to 2 deg C)Atlantic Layer
Cold, saltier “Cold Halocline”layer insulates the surface icefrom the deeper warm Atlantic
Layer
The Atlantic waters carry heat into the region.
The “cold halocline” waters, which insulate the ice from the underlyingwarm Atlantic waters, come from the Arctic shelves and the Pacific
waters.
The combination of the pathways of these waters determines howmuch heat can escape upwards to melt ice.
?
?
?
150o W
120
o W
90
o W
120 oE
180oW
70oN
75oN
80oN
85oN
Mendeleev Ridge
ChukchiBorderland
Pathways of nutrient-rich Pacific waters?
The Pacific waters are the mostnutrient-rich waters in the
Arctic.
They enter the Arctic in threemain flows,
- though Barrow Canyon,- through Herald Canyon- between the Herald and
Hanna Shoals.
Some fraction continues east-ward along the north coast of
Alaska
Some appears to head off intothe deep Arctic basin
The depth these waters reach inthe Arctic depends on their den-sity (i.e. their temperature and
salinity).Measurements from theBeringStrait show these properties to
be changing over the lastdecade.
What causes these changes andhow will they affect Arctic eco-
systems?
Arctic Climate Change?
>1.0>
>0.7>
>0.5>
>0.4>
>0.3>
>0.2>
>0.1 150
o W
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o W
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180oW
75oN
80oN
85oN
150o W
120
o W
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150 oE
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80oN
85oN
150o W
120
o W
120 oE
150 oE
180oW
75oN
80oN
85oN
150o W
120
o W
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150 oE
180oW
75oN
80oN
85oN
150o W
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o W
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85oN
150o W
120
o W
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150 oE
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‘93
‘98‘95
‘97‘94
‘96Tmax
/oC
Maximum temperatures in the Atlantic core from the Scicex and AOSexpeditions. Note the warming of the core in the Chukchi Borderlandregion between 1993 and 1998, and the excursion of warm water into
the deep Arctic basin (1996 and 1997, ca.79N)
135o W
90
o W
45 oW
0o
45o E
90
o E
135 oE
180oW
70oN
80oN
Chukchi Borderland Cruise 2002
A single cruise oceanographic surveyof the Chukchi Borderland and
Mendeleev Ridge region, aboard theUSCGC Polar Star in autumn 2002.
CTD sections
3 oceanographic moorings, inplace for the ca. 1 month duration ofthe cruise.
Barrow200 nm
SBE-16 S/Nwith pressure
________
Depth _______
MOORING ID: __________CBL-B
CHUKCHI
BORDERLAND
02
RCM-7 S/N ________Depth _______m.
Double 17in. Glass Float
Double 17in. Glass Float
SBE-16 S/Nwith pressure
________
Depth _______
RCM-7 S/N ________Depth _______m.
EG&G 8242S/N: ______
EG&G 8242S/N: ______
RCM-7 S/N ________Depth _______
5/16“ Kevlar_______m.
5/16“ Kevlar_______m.
5/16“ Kevlar_______m.
5/16“ Kevlar_______m.
5/16“ Kevlar_______m.
5/16“ Kevlar_______m.
100
101m.
350
351m.
800m.
3
3
443
100+144
3
5
Double 17in. Glass Float
5/16“ Kevlar_______m.3
97
Double 17in. Glass Float
5/16“ Kevlar_______m.100+91
2m. Chain (Long Link)
AnchorDry Wt. = _______lbs.
BottomDepth: _______m.1000 1400
30“ Steel Float
Pieps
XT-6000 S/N ______Depth ____m.
2m. Chain (Long Link)
Chukchi Borderland Moorings 2002
Three moorings- deployed across the boundary current,- in place for ca.1 month- hourly measurements of temperature,salinity and water velocity in the mainwater layers of the Arctic Ocean
This will provide information on- the physical structure, transport andvariability of the boundary current- the variability of the interactionsbetween Pacific and Atlantic waters
Moorings will be recovered at the end ofthe cruise
A series of CTD (Conductivity and Temperature with Depth) stationswill measure the temperature and salinity of the Arctic (Atlantic and
Pacific) waters in a set of 12 sections in the Chukchi Borderland/Men-deleev Ridge regions.
Teams from Scripps, LDEO and OSU will take water samples for chem-ical analysis of oxygen, nutrients, and tracers of Atlantic, Pacific and
river waters.
Example of CTD Rosettesystem from RV Alpha Helix(Photos from NPMR, UAF)
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o W
5 oW
90
o E
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Barrow200 nm
Chukchi Borderland CTD Work 2002
The combination ofthese data tell us thepathways and origins
of the waters, andcomparison with
older data indicateshow the system is
changing
The floating classroom
Ms Gail Grimes, a High School sci-ence teacher from Washington
State, and her classes, from LakeStevens High School, will also takepart in the cruise. Ms Grimes will
sail on the Polar Star and send backdaily reports and photos to a public
website, both for her classes andfor others interested in following the
cruiseMs Gail Grimesand her class
150o W
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o W
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o W
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The Influence of the Mendeleev Ridge and the ChukchiBorderland on the Large-scale Circulation of the Arctic
Ocean
R. Woodgate, K. Aagaard, J. Swift, B. Smethie, K. Falknerin collaboration with E. Carmack, F. McLaughlin
= delineate the pathway of theArctic Ocean Boundary Current,past the Mendeleev Ridge and
through the Chukchi Borderland
= assess the input from the boundarycurrent and the shelves to the
deep Arctic Ocean
= understand and quantify the pathways and transformations
of the Pacific waters
= describe thehorizontal and
vertical structure ofthe boundary current,
and estimateits transport
= quantify temporal change,by combining this survey
with historic data
Mendeleev Ridge
ChukchiBorderland
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