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Variability of Ice and Ocean Fluxes in the Arctic/Sub-Arctic Domain Michael Karcher,

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.

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Variability of Ice and Ocean Fluxes in the Arctic/Sub-Arctic Domain Michael Karcher,

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  1. 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, 2003Seattle, Washington, USA

  2. AOMIP NAOSIM Arctic Ocean Model Intercomparison Project Freshwater content

  3. NAOSIM model setup Rüdiger Gerdes, Frank Kauker, Cornelia Köberle, Jennifer Brauch, Jörg Hurka, Kerstin Fieg • 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

  4. Temperature and Salinity Observations in the West Spitzbergen Current (Fram Strait Branch)

  5. NAOSIM Tpot °C Propagation of temperature anomalies in the Arctic Ocean Velocity cm/s 1960s 1990s Gerdes et al., GRL 2003

  6. NAOSIM Arctic warming events cold anomaly (→ NABOS) Temperature at the level of the temperature maximum See Karcher et al., JGR 2003

  7. NAOSIM 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

  8. NAOSIM model results (Karcher et al., in prep) Barents Sea salinity outflow Ice balance ? ? inflow

  9. NAOSIM large net import Barents Sea ice im- and export large net export

  10. Maximum densities in deep Barents Sea outflow Observed high Now. Zem. Polynia Icegrowth Observed low Observed medium values Observations: Schauer et al, 2002

  11. NAOSIM Barents Sea dense water outflow: mean densities: sea-ice balance variability seems as influential as AW inflow variability peak densities: local ice formation/salt release

  12. NAOSIM Arctic halocline 1968 vs. 1998 Reduction of Arctic Ocean Freshwater pool

  13. NAOSIM Freshwater Inventory (total watercolumn) Arctic Ocean • 14000 • km3 Change in trend or again decadal fluctuation? Nordic Sea + 4000 km3

  14. 1994 1995 SSS Ano-malie 1996 1997

  15. NAOSIM Fram Strait 0-90m Denmark Strait 0-90m Arctic Subarctic low-saline surface outflow Significant alterations

  16. NAOSIM Liquid Freshwater fluxes Nordic Sea (ref. 34.8) Fram Strait Canadian Arch. Iceland-Faroe Faroe-Scotland Denmark Strait

  17. NAOSIM Phases of net freshwater surplus Nordic Sea Freshwater budgets (NAOSIM NCEP hindcast) Surface fluxes Advective sea-ice balance Residual freshwater Advective liquid balance

  18. NAOSIM Nordic Sea freshwater budget: variability of sea-ice balance at least as important as variability of liquid balance

  19. NAOSIM [Dickson et al., 2002] Deep Denmark Strait Salinity Black: NAOSIM model results Blue: Observations [Dickson et al., 2002] shifted -0.035 Obs

  20. NAOSIM • DSOW signals: • Temperature: • Decadal signals • Salinity: • Decadal signals plus freshening trend • weaker in model than in observations • ... due to restoring?

  21. NAOSIM • 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, …

  22. NAOSIM Temperature signals passing along the East Greenland Coast 0-90 m Black: Fram Strait Blue: Denmark Strait 90-280 m 280-970 m

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