variability of ice and ocean fluxes in the arctic/sub-arctic domain michael karcher,
DESCRIPTION
Variability of Ice and Ocean Fluxes in the Arctic/Sub-Arctic Domain Michael Karcher, R. Gerdes, F. Kauker, C. Köberle, U. Schauer Alfred Wegener Institute for Polar and Marine Research. SEARCH Open Science Meeting October 27, 2003 Seattle, Washington, USA. AOMIP. NAOSIM. - PowerPoint PPT PresentationTRANSCRIPT
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Variability of Ice and Ocean Fluxes
in the Arctic/Sub-Arctic Domain
Michael Karcher, R. Gerdes, F. Kauker, C. Köberle, U. Schauer
Alfred Wegener Institute for Polar and Marine Research
SEARCH Open Science MeetingOctober 27, 2003Seattle, Washington, USA
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NAOSIM
Freshwatercontent
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NAOSIM model setup
MOM 2 based coupled to sea-ice model
0.25o resolution on rotated spherical grid
30 levels
Open boundary at 50oN
Initial condition: EWG + Levitus et al. (1994)
Spin up: 20 years climatology with daily variability based on ECMWF
NCEP forcing 1948-2002
Rüdiger Gerdes, Frank Kauker, Cornelia Köberle, Jennifer Brauch, Jörg Hurka, Kerstin Fieg
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Temperature and Salinity Observations in the West Spitzbergen Current (Fram Strait Branch)
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Propagation of temperature anomalies in the Arctic Ocean
Velocity cm/s
Tpot°C
Gerdes et al., GRL 2003
1990s
1960s
NAOSIM
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Arctic warming events
Temperature at the level of the temperature maximum
cold anomaly(→ NABOS)
NAOSIM
See Karcher et al., JGR 2003
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Propagation of temperature anomalies:
Warmest events in 60s and 90s
90s event outstanding in intensity and spatial extent
(large volume flow and reduced heat loss)
Important role of the Barents Sea
NAOSIM
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Barents Sea salinity
inflow
outflow
? ?
NAOSIM model results(Karcher et al., in prep)
Ice balance
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Barents Sea ice im- and export
large net export
large net import
NAOSIM
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Maximum densities in deep Barents Sea outflow
Observed low
Observed high
Observations: Schauer et al, 2002
Observed medium values
Now. Zem. Polynia Icegrowth
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Barents Sea dense water outflow:
mean densities:
sea-ice balance variabilityseems
as influential as AW inflow variability
peak densities:
local ice formation/salt release
NAOSIM
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Arctic halocline 1968 vs. 1998
NAOSIM
Reduction of Arctic Ocean Freshwater pool
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Arctic Ocean
Nordic Sea
-14000 km3
+ 4000 km3
Change in trend or again
decadal fluctuation?
Freshwater Inventory (total watercolumn)NAOSIM
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SSS Ano-malie
1994 1995
1996 1997
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Fram Strait 0-90m
Denmark Strait 0-90m
Arctic Subarctic low-saline surface outflow
Significant alterations
NAOSIM
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Fram Strait
Denmark Strait
Iceland-FaroeFaroe-Scotland
Canadian Arch.
Liquid Freshwater fluxes Nordic Sea (ref. 34.8)NAOSIM
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Advective liquid balance
Surface fluxes
Residual freshwater
Nordic Sea Freshwater budgets (NAOSIM NCEP hindcast)
Phases of net freshwater surplus
Advective sea-ice balance
NAOSIM
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Nordic Sea freshwater budget:
variability of sea-ice balance at least as important as
variability of liquid balance
NAOSIM
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Deep Denmark Strait Salinity
Black: NAOSIM model results
Obs
Blue: Observations [Dickson et al., 2002]shifted -0.035
[Dickson et al., 2002]
NAOSIM
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DSOW signals:
Temperature:
Decadal signals
Salinity:
Decadal signals plus freshening trend -weaker in model than in observations
... due to restoring?
NAOSIM
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What‘s up next:
• Freshwater storage and release dynamics (e.g. ASOF-FAST)
• Model intercomparison / Atlantic Water dynamics (AOMIP)
• Comparison of model results with new analyses of modern and historic data (…T, S, Tracer)
• and as always: model improvement, new forcing data sets, …
NAOSIM
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NAOSIM
0-90 m
90-280 m
280-970 m
Black: Fram Strait
Blue: Denmark Strait
Temperature signalspassing along the East Greenland Coast