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Arctic Freshwater update Cube 43 Alan Condron & Peter Winsor 20 th February

Arctic Freshwater update Cube 43 Alan Condron & Peter Winsor 20 th February. Original Questions Asked. How well does the ECCO2 model represent the Arctic? Is it realistic?

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Arctic Freshwater update Cube 43 Alan Condron & Peter Winsor 20 th February

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  1. Arctic Freshwater updateCube 43Alan Condron & Peter Winsor 20th February

  2. Original Questions Asked • How well does the ECCO2 model represent the Arctic? Is it realistic? • A recent paper by Serreze et al. presented an observed freshwater budget for the Arctic. How well can the model reproduce this? • Over time the model Arctic becomes increasingly salty (reduced volume of “freshwater”). Why is this?

  3. There is a rapid reduction in the amount of “freshwater” as the arctic becomes saltier and losses its vertical stratification Cube 22 Cube 43 Vertically integrated freshwater Start to lose Beaufort gyre circulation After 30 years 1992 2002 Time Total freshwater: 67552 km3 Total freshwater: 74714 km3 Total freshwater: ~32000 km3

  4. Changes in freshwater volume over time Observed: 74345 km3 Cube 22 Cube 43 (blue) and 47 (red) A longer simulation might be useful in resolving the initial decline in freshwater volume?

  5. Towards an improved arctic freshwater budget for the cube runs Consider transports of water, ice and salt in/out of the model Arctic via Fram Strait, Bering Strait, Canadian Archipelago, Barents Sea etc, with the aim of identifying why the cube runs are becoming saltier.

  6. Arctic gates Bering Strait Amundsen Sea M’Clure Strait Canadian Archipelago Queen Elizabeth Islands Nares Strait Barents Sea Fram Strait

  7. Examples Fram Strait Fram Strait Bering Strait

  8. Volume transports (monthly data) * Fahrbach et al., Woodgateet al, Schauer et al., Rudels et al., Observational time series exist for this period to allow model comparison.

  9. Liquid freshwater transport (Ft)(monthly output cube 43) Importing Freshwater FT = U * (1-(sal/34.8) where U is volume transport. Note that positive and negative FT are considered Exporting Freshwater

  10. Sea Ice freshwater transport (monthly cube 43) * Rothrock et al., Prinsenberg et al. Main ice export via Fram Strait. Export through Canadian Archipelago is primarily in liquid form.

  11. Total (ice + water) Freshwater Transport (anomaly from 1992-2001 av.)

  12. Total (Ice + water) freshwater transport anomalies (from 1992-2001 av.) Arctic freshwater is leaving via the Canadian Archipelago

  13. A closer look at the Canadian ArchipelagoIce + water freshwater transport

  14. NAO and Freshwater Transport Correlation NAO-total freshwater: r= -0.25 NAO-Can. Arch.: r= -0.16

  15. Towards an Arctic basin freshwater budget ATMOSPHERE ATMOSPHERE Precip = 3253 Precip = 3253 Evap=1299 Evap=1299 OCEAN OUT = 8874 IN = 8591 Imbalance = -283 OCEAN OUT = 10372 IN = 9494 Imbalance = -878 Bering = 2263 (-150) LAND Run-off Bering = 2489 LAND Run-off R = 3000 R = 3000 Barents Sea = 398 (+58) Barents Sea = 340 Canadian Arch. (Water) = 2174 (-976) Canadian Arch. (Water) = 3153 Canadian Arch. (Ice) = 8 Canadian Arch. (Ice) = 158 Barents (Ice) = 104 Fram Strait (water) = 2405 Fram Strait (water) = 2555 (+150) Fram Strait (ice) = 2265 Fram Strait (ice) = 2336 (+71) Cube 43 From Serreze et al. (in press)

  16. Where to from here…. • Establish why freshwater is exported through the Canadian Archipelago. Is it a response to 1990s wind forcing (strong NAO) and loss of Beaufort gyre freshwater? • Examine cube 47 - more realistic river run-off from P.Winsor • Consider P-E from NCEP. • Compare model overflows in 1990s to observational time series data (Fram and Bering data covering model run period).

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