Lateral Mixing across Ice Meltwater Fronts of the Chukchi Sea Shelf Kofan Lu 1 , T. Weingartner 1 , S. Danielson 1 , P. Winsor 1 , E. Dobbins 1 , K. Martini 2,3 , and H. Statscewich 1 1 School of Fisheries and Ocean Sciences, University of Alaska, Fairbanks, Alaska, USA. 2 Joint Institute for the Study of the Atmosphere and Oceans, University of Washington, Seattle, Washington, USA. 3 Pacific Marine Environmental Laboratory, NOAA, Seattle, T1:2012 T2:2013 Geophysical Research Letters, Volume 42, Issue 16 28 August 2015 Pages 6754–6761, DOI: 10.1002/2015GL064967
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Lateral Mixing across Ice Meltwater Fronts of the Chukchi Sea ShelfKofan Lu1, T. Weingartner1, S. Danielson1, P. Winsor1, E. Dobbins1, K. Martini2,3, and H. Statscewich1
1School of Fisheries and Ocean Sciences, University of Alaska, Fairbanks, Alaska, USA.2Joint Institute for the Study of the Atmosphere and Oceans, University of Washington, Seattle, Washington, USA.3Pacific Marine Environmental Laboratory, NOAA, Seattle, Washington, USA.
T1:2012T2:2013
Geophysical Research Letters, Volume 42, Issue 16 28 August 2015 Pages 6754–6761, DOI: 10.1002/2015GL064967
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• 1 dbar-averaged CTD data (CSESP)
• Nominal spacing of 15 km
Air-Se
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BSWMW
WW
BSW MW
WW
T1:2012T2:2013
Density: WW>BSW>MW
BSWMW
WW
BSW MW
WW
Density: WW>BSW>MW
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M1
M2
BSW MW
WW
BSWMW
WW
Without External Forcing
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BSWMW
WW
BSW MW
WW
Without External Forcing
Density: WW>BSW>MW
S N
S N
Bering Sea
Inflow
Bering Sea
Inflow
Initial Condition• Uniform WW• T = -1.4° C• S = 33
Bering Sea Inflow• 100 km width• ~0.25 Sv• T = 5° C• S = 30
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S N
S N
Ice
Ice Layer• Thickness: 2 meters• Concentration: 100%• No snow cover
Surface Forcing• Diurnal shortwave radiation• No longwave radiation• Air temperature 10 °C
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Temperature
Salinity
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Melt water layer evolution1. Fresh water formed
because of ice melting2. Pushed back/mixed by
dense Winter Water
Temperature
Salinity
Temperature
Salinity
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Melt water evolution3. Melt Water layer occurs on southern edge of ice extent4. BSW inflow separates MW and WW layers
MW
MW
Temperature
Salinity
Temperature
Salinity
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MW
MW Ice
Surface Forcing• Realistic shortwave radiation• Apply surface heat flux from observations
Temperature
Salinity
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Instability-Induced Eddies1. Density gradient -> baroclinic instability2. Exchanges between potential energy and kinetic energy
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1 23 ζ
Ice Distribution1. Eddies-supported BSW
transports under ice layer 2. Instability-induced eddies
have significant effects on ice melting
3. BSW mean flow impacts the southern boundary of ice extent
T1:2012T2:2013
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ζ
Wind Forcing• Instability-induced eddies
- Destabilizing surface buoyancy- Enhance gravitational instability
• BSW Stratification- Increase mixing?- Restrain warm water intrusion?
• Ice/current motion- Dragged by wind?- Interacted with warm water?
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WIND ρA
ρM
ρB ρW
ρA<ρM<ρB<ρW
S N
ζ
Summary
• Heat flux associated with eddies along MW/BSW front is a significant contributor to seasonal ice retreat
• Heat flux associated with the mean flow is as important as the atmospheric heat flux
• Wind is important to the formation of MIZ instabilities by altering the structure of MW fronts and BSW stratification
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