CATS workshop

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The circulation of summer Pacific Water in the
Arctic Ocean
Michael Steele, Jamie Morison, Wendy Ermold,
Ignatius Rigor, Mark Ortmeyer Polar Science
Center, Applied Physics Laboratory, University of
Washington, Seattle, WA 98105 USA Koji
Shimada Jamstec Marine Science and Technology
Center, Yokosuka, Japan
surface layer
summer Pacific water
S
T
Atlantic layer
SCICEX96 (cast 43)
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Lateral extent of summer Pacific water
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Why do we care about Pacific water?

• Global freshwater circulation
• Major component of the Arctic Ocean halocline
• Nutrient river through the Arctic Ocean

Nutrients!
North Water Polynya
Tremblay et al. (2002)
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Water masses in the Bering Strait region
following Coachman et al. (1975) others
Bering Sea Water (BSW)
Alaska Coastal Water (ACW)
Siberian Coastal Current (SCC)
Alaska
LDI
BDI
Russia
Gulf of Anadyr Water (GAW)
Bering Shelf Water (BSW)
BSW colder, salty, high nuts ACW warmer,
fresher, low nuts
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There are 2 types of summer Pacific water in
the Arctic Ocean!
S
T
Shimada et al., 2001

• ACW Alaskan Coastal Water
• sBSW summer Bering Sea Water

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How far downstream can we detect a summer
Pacific water Tmax ?
NPEO North Pole Environmental Observatory
At least as far as the Ellesmere Island Shelf
Break... but is this true for all years? and
what exactly is getting there sBSW? ACW?
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Hydrographic surveys
http//psc.apl.washington.edu/northpole
Twin Otter tent
Years 2000/03 stations
CTD bottle obs
NPEO also includes drifting buoys moorings
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Lateral extent of summer Pacific water
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Summer Pacific water The view from 1993
1993 cruise data (SCICEX/Larsen/Melling/ ARKIX/4,
NewtonSotirin)
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Tmax
z
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Schematic circulation of summer Pacific water in
1993
BSW
ACW
sBSW
a separated flow regime w.r.t. Pacific water
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And now, for the obligatory Arctic Oscillation
discussion
positive
AO index
neutral
negative
The sea ice response
Negative AO index
Chukchi Sea -gt Ellesmere Island 6 years
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The area north of Ellesmere Island Iceshelf
(Newton Sotirin, 1997) NPEO (Steele et al.,
2003)
sBSW Tmax north of Ellesmere Island
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Summer Pacific Water circulation Low (1980s)
vs. High (early-mid 1990s) AO index

• Mixed summer Pacific water regimes throughout the
  Arctic Ocean
• including in outflows through the western
  Canadian Archipelago?
• Old (i.e., no Tmax) sBSW north of E.I.

• Separated summer Pacific water regimes in some of
  the Arctic Ocean
• including through western/ eastern Canadian
  Archipelago channels?
• New (i.e., warm Tmax) sBSW at EISB

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A new look at T(z) profiles in the Canadian Basin
of the Arctic Ocean, especially under AO
conditions.

• Theres 3 Pacific water types
• ACW
• Summer BSW
• Winter BSW

• is there winter ACW?
• T S data say no
• T, S, O2 data (Itoh Shimada, 2003) say maybe

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What about interannual source variability?!
Aagaard, Woodgate, Weingartner
http//psc.apl.washington.edu/HLD/Bstrait/bstrait
.html
Theres a lot of it! not to mention variations
in the Chukchi Sea.
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Why dont we see this in our data, downstream
from this (highly varying) source?
high variance
low variance
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Why dont we see this in our data, downstream
from this (highly varying) source? (Part 2)
Theres some evidence for source
variability downstream in the Arctic Ocean, but
Our observations are explainable mostly by
changes in circulation, rather than by changes
in the character of the inputs.
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What about chemical tracers?
Pacific water () in the upper 30 m (using the
N/P ratio).
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93 96
50
00 01
K. Falkner, OSU Jones et al. (1998)
AO index drops through the latter 1990s ?
Transpolar Drift Stream has less Pacific influence
Confirms our T/S data. But theres more to do
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Whats the role of the North American boundary
undercurrent?

• Lots of question marks
• Limited evidence suggests a deep eastward
  current, with interannually varying vertical
  shear in the halocline.
• This ? high interannual variability in the
  transport of halocline water masses within the
  current

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The freshwater switchyard A good place to
detect the origins of freshwater thats about to
leave the Arctic Ocean

• 3 project components
• Large-scale hydrochemical sections (Schlosser
  Smethie)
• Boundary current section at the shelf break
  (Steele)
• Sea ice transport studies (Kwok)

Obs spring 2003-2007
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Details
Alert-NP survey Twin Otter aircraft, 6-9
stations THICR THrough-Ice CTD-Rosette,
measuring T, S, O2, oxygen isotopes, tritium/3He,
CFCs, barium, nutrients. Samples to be drawn
at Alert.
Boundary current survey helicopter, 6-9
stations CTD-O, XCP, surface layer bottles.
Sea ice transport studies satellites uice AMSR
passive µwave, ENVISAT SAR hice altimeters on
IceSAT (laser) ENVISAT, CryoSAT (radar)
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Switchyard03
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Switchyard slope section03
The isopycnals are flat as a pancake! ? very
little vertical shear I need to look at the
wind/ice stress forcing
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Switchyard slope section03
BSW / ACW ?

• Summer Pacific water Tmax
• Its recovered, but still cool
• S 32 on the slope
• S gt 32 on either side
• NPEO station 6 Tmax ? slope Tmaxs

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Switchyard and NPEO sections
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Thanks to colleagues at PSC, IOS, elsewhere
for data and ideas!