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An atmosphere-ice-ocean reanalysis of the Arctic for the IPY Lars Axell and Per Kållberg Research and Development Swedish Meteorological and Hydrological.

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Presentation on theme: "An atmosphere-ice-ocean reanalysis of the Arctic for the IPY Lars Axell and Per Kållberg Research and Development Swedish Meteorological and Hydrological."— Presentation transcript:

1 An atmosphere-ice-ocean reanalysis of the Arctic for the IPY Lars Axell and Per Kållberg Research and Development Swedish Meteorological and Hydrological Institute

2 09/03/10 Signatur Outline Description of the coupled model system Results from the Arctic reanalysis Conclusions so far Outlook

3 09/03/10 Signatur Description of the coupled model system Atmosphere: –Circulation model: HIRLAM version 7.2 –Data assimilation: 4D-Var 6-hour cycle –Observations: TEMP, PILOT, AIREP, SYNOP, SHIP, AMSU-A over sea and ice – from ECMWF MARS archive –40 hybrid levels (top at 10 hPa) –lateral boundary conditions – from ERA-interim Ocean: –Circulation model: HIROMB version 4.1 –Data assimilation: Optimal Interpolation (OI) –Observations: NCEP SST, AMSR-E SIC, S/T profiles (ships, buoys, gliders, moorings, Ice-Tethered Profilers) –208 z-levels (5-25 m resolution) Horizontal grid: 306x306, ~12 nm resolution (both HIRLAM and HIROMB) Rotated coordinate system: South pole at 4ºS, 0ºW (both HIRLAM and HIROMB) model domain and bathymetry of HIROMB

4 09/03/10 Hiromb OI coast following structure functions

5 09/03/10 Signatur Description of the coupled model system (cont.) Exactly the same horizontal grid as HIRLAM (no separate coupler) Bathymetry data: –International Bathymetric Chart of the Arctic Ocean (IBCAO) –Regional data from the Baltic Sea –Scripps Institution of Oceanography, UCSD (satellite altimetry and depth soundings) 47 rivers (annual means) Open boundaries: –Salinity and temperature from World Ocean Atlas 2005, monthly means –Sea levels: inverse barometer effect

6 09/03/10 Signatur The coupling Coupling time step: 6 hours HIROMB is forced by HIRLAM-fields (winds, air temperature, air pressure, cloudiness, etc.) HIRLAM reads fields of ice concentration and SST from HIROMB HIROMBs analysis after its forecast; HIRLAMs analysis before its forecast Analyses performed here

7 09/03/10 Signatur Number of ocean observations (2005-2007) (note the logarithmic scale) temperaturesalinity

8 09/03/10 Signatur March 2005 September 2005 hirlam-hirombsea ice concentration %era_interim

9 09/03/10 Signatur March 2005 September 2005 surface salinitysurface temperature Monthly mean fields

10 09/03/10 Signatur monthly mean ocean-air net energy exchange, march 2006 hirlam/hiromb era interim red=downwards, blue=upwards

11 09/03/10 Signatur monthly mean ocean net energy exchange, september 2006 hirlam-hiromb era interim

12 09/03/10 Signatur hiromb ice-drift march 2006 hirlam 10-metre wind march 2006

13 09/03/10 Signatur hiromb ice-drift March 2006 hirlam 10-metre wind March 2006 hiromb ice-drift september 2006 hirlam 10-metre wind september 2006

14 09/03/10 Signatur hirlam wind-stress march 2006 hirlam wind-stress september 2006

15 09/03/10 Signatur Arctic Sea Ice Extent (reanalysis updated until 200610) Ice extent = sum of area with at least 15 % sea ice

16 09/03/10 Signatur Transect across Fram Strait Date: 2005-09-15 (Greenland left) Temperature ( ° C) Velocity (cm/s) Salinity (psu) Northward transport of high-saline, warm water west of Svalbard Southward transport of low-saline, cold water off Greenlands shelf Data assimilation of mooring data (S/T) Net southward volume transport: 1 Sverdrup (mean 2005) Net northward heat transport: 10 TW (mean 2005)

17 09/03/10 Signatur Fluxes through Fram Strait (monthly means) Volume flux (unit: Sverdrup) Heat flux (unit: TW) (0 deg reference) 2005 mean: +9.5 TW 2006 mean: -25.4 TW 2007 mean: ?

18 09/03/10 Signatur Heat budget (fluxes in TW into the Arctic) (proper Arctic except Barents Sea) Large total differences between 2005 and 2006 Largest difference in the Fram Strait Bering Strait Lancaster Strait + Nares Strait Fram Strait Spitzbergen- Russia Total 2005+3.1-11.5+9.5+19.2+20.3 2006 preliminary +1.2-10.9-25.4+22.1-13.0

19 09/03/10 Signatur Changes in total ice volume (proper Arctic except Barents Sea) 2005-04-16 12:00 UTC 2005-09-18 00:00 UTC Change: 5622 km3 2006-04-24 12:00 UTC 2006-09-29 06:00 UTC Change: 8600 km3 Ice decrease 2005:5 622 km3 Ice export 2005: 482 km3 (9%) Ice decrease 2006:8600 km3 Ice export 2006: 377 km3 (4%) ------------------------------------------------------------------------------------------- BEDAFRBSTot ------------------------------------------------------------------------------------------- 20057310227334482 20065682241-2377 -------------------------------------------------------------------------------------------

20 09/03/10 Signatur Conclusions Common horizontal grid – simplifies coupling 23 months reanalysed so far (Jan. 2005 to Nov. 2006) Ice decrease in 2005 and 2006 due to regional melting, not ice export Lateral oceanic heat flows into the Arctic Larger in 2005 than in 2006 Compared to ERA-interim, our analysis has –consistent air-sea energy exchanges between the spheres –more detailed sea ice analyses –an ocean component!

21 09/03/10 Signatur Outlook Complete three years, 2005-2007 Replace HIROMB bulk formulae with HIRLAM fluxes Re-calculate lateral oceanic budgets (volume, heat, freshwater) Write a report and a paper END


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