Climatology of the Arctic Ocean based on NEMO results

Transcription

1 Climatology of the Arctic Ocean based on NEMO results SU Jie LI Xiang, ZHANG Yang Key Lab of Polar Oceanography and Global Ocean Change Ocean University of China, Qingdao, China Cooperator: Youyu Lu, Zeliang Wang, Frederic Dupont Bedford Institute of Oceanography, Dartmouth, Canada

2 Outline Motivation Model description Basic results of -y s standard run (global and Arctic) Scientific interest Pacific inflow s effect on sea ice distribution and upper layer ocean How to get a reasonable middle layer water from Atlantic with a coarse resolution model? SU Jie,OUC AOMIP,WHIO,.

3 Motivation Realistic modelling Arctic conditions (climatology and variability) and its influences on global ocean climate Understanding the Pacific inflow and Atlantic inflow s influences on Arctic Ocean SU Jie,OUC AOMIP,WHIO,. 3

4 Model Description A coupled ice-ocean model under the NEMO framework the Ocean model: OPA (Madec, et al., 998) ; The ice model: LIM (Fichefet and Morales, 997;Christian and Gurvan) Initial field: January climatology of temperature and salinity based on PHC3. Sea ice thickness: 3m in northern hemisphere; m in southern hemisphere Surface forcing: OMIP daily climatology (from957 - ERA-4) of wind stress, air temperature, cloud cover, relative humidity, precipitation, wind speed; SSS restored Boundary forcing Arctic model takes boundary forcing from global model SU Jie,OUC AOMIP,WHIO,. 4

5 Model s Grid Tri-polar grids The horizontal resolution: degrees Mercator mesh with finest resolution in CAA is 5km The vertical resolution is 46 levels (interval: 6-5m) The time step is 8s. Standard run include both global and arctic domain Model is integrated for years ORCA glob grids ORCA actc grids

6 Basic results of -y s global and Arctic standard run Ice area Ice concentration Ice motion Ocean current (upper m and 45m) Sea temperature field (m and 45m) Vertical temperature profile SU Jie,OUC AOMIP,WHIO,. 6

7 Total ice area of Arctic SU Jie,OUC AOMIP,WHIO,. 7

8 SSM/I 979- Sea ice concentration Modeled-glob Modeled-actc March September

9 NSIDC 979- Sea ice motion Modeled-glob Modeled-actc March September

10 upper m Ocean current 45m March September

11 m sea temperature PHC3. Modeled-glob Modeled-actc March September

12 PHC3. 45m sea temperature Modeled-glob Modeled-actc March September

13 Vertical temperature profile SU Jie,OUC AOMIP,WHIO,. 3

14 Station,,3,5,6,7 SU Jie,OUC AOMIP,WHIO,. 4

15 Station 4,8,9,, SU Jie,OUC AOMIP,WHIO,. 5

16 Station,3 SU Jie,OUC AOMIP,WHIO,. 6

17 How to get a reasonable middle layer water from Atlantic in a coarse resolution model? SU Jie,OUC AOMIP,WHIO,. 7

18 ¼ degree resolution SU Jie,OUC AOMIP,WHIO,. 8

19 Velocity section of Fram Strait OPA SODA CFSR Schauer et al.(4) Oct. 998 (Obs.) depth(m) V(cm/s) Oct998 opa depth(m) V(cm/s) Oct998 CFSR SU Jie,OUC AOMIP,WHIO,. lon lon Adding Neptune effect (Hollway,99) did help to increase the current of Atlantic inflow, but still work not well for the vertical Temp. profile depth(m) V(cm/s) Oct998 soda

20 45m sea temperature (September) PHC3. initial model result model result - initial SU Jie,OUC AOMIP,WHIO,.

21 Max Temp. depth of Middle layer water (September) PHC3. initial model result model result - initial SU Jie,OUC AOMIP,WHIO,.

22 Experiments on vertical turbulence problem The vertical turbulent coefficient include three items: TKE (turbulent closure scheme) DDM (double diffusion mixing) Item caused by choosing horizontal mixing scheme ε ε l e c k e e A k e N A k v k u e A t e vm vt vm 3 / = e l C A k k vm = n vm vt P A A / = ( T ) A D lt lt R = + R = r r r r r r = k i r ρ ρ = k j r ρ ρ + k T r r A k lt ) ( iso-level iso-neutral

23 Experiments on vertical turbulence problem 3 all R = r r r r r + r Exp:limit wslp to e-5 Exp:limit r,r to e-6 Exp3:limit Alt (under ice ) to e-7

24 Two years experiments SU Jie,OUC AOMIP,WHIO,. 4

25 Summary and discussion The modeled sea ice results can represent the seasonal cycle of Arctic sea ice in basic pattern. Ice area agrees well with those calculated by SSMR-SSMI ice concentration. The Beaufort gyre and the transpolar drift are showed obviously in the modeled ice drift and upper m current field. y run fails to reproduce the Atlantic layer in ice covered region, especially in Euro-Asian Basin. This problem can be solved by enhance model resolution. Using a coarse model, the problem of Atlantic layer is possibly caused by too weak transport though Fram Strait and too strong vertical diffusion which caused by iso-neutral horizontal mixing scheme. Limit the advection diffusion coefficient can partly improve the results. SU Jie,OUC AOMIP,WHIO,. 5

26 Thank you for your attention! Any Question? SU Jie,OUC AOMIP,WHIO,. 6