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.

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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

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BSWMW

WW

BSW MW

WW

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Density: WW>BSW>MW

BSWMW

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BSW MW

WW

Density: WW>BSW>MW

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M1

M2

BSW MW

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BSWMW

WW

Without External Forcing

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BSWMW

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BSW MW

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Without External Forcing

Density: WW>BSW>MW

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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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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

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Melt water layer evolution1. Fresh water formed

because of ice melting2. Pushed back/mixed by

dense Winter Water

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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

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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

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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

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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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