1. Dynamics of the Norwegian Atlantic Current from high resolution modeling Marie-Noëlle Houssais Christophe Herbaut, Antoine Martin, Dorotea Iovino, Anne-Cécile Blaizot LOCEAN, CNRS/Université Pierre et Marie Curie, Paris, France FAMOS meeting - October 24-26, 2012

2. 119 34 5 -36 Nordic Seas heat budget Segtnan et al., 2011 74 1 Can eddy heat fluxes contribute to the heat budget residual in the NAwC ?

3. FAMOS meeting - October 24-26, 2012 Nordic Seas heat budget ERA-Interim 1997-2991 - annual mean Surface heat loss 30 TW

4. FAMOS meeting - October 24-26, 2012 High resolution modeling of the GIN Seas Sea surface temperature NEMO/ORCALIM ORCA025 Arctic-North Atlantic 12-16 km resolution in the Nordic Seas ORCA025-AGRIF 1/16° 3-4 km resolution the Nordic Seas ERA-I nterim forcing 1989-2011

5. FAMOS meeting - October 24-26, 2012 Mean surface circulation 74.1°N, 03.7°W Svinoy

6. FAMOS meeting - October 24-26, 2012 NAwC : Along-slope velocity Svinoy section Annual mean (1994-2005) Two distinct branches : « slope » and « front » Increased horizontal resolution  stronger flow in both branches 1/4 ° 1/16 ° Mooring data Skagseth et al, 2008

7. FAMOS meeting - October 24-26, 2012 Too narrow boundary currents (enhanced topography influence) Enhanced AW core temperature and salinity Observations (Skagseth et al. 2008)Model (1/16°) Hydrographic properties in the NAwC - Svinoy section - July 1998

8. FAMOS meeting - October 24-26, 2012 Surface eddy kinetic energy : Annual mean (see also Koszalka et al, 2011, 2012 ) AVISO geostrophic velocities Model (1/16°) Surface drifters

9. FAMOS meeting - October 24-26, 2012 Surface velocity perturbations Lofoten Basin - March 1998

10. Idealized 2-layer ocean Mysak and Schott, 1977 Typical eddy scale: about 40-50km Larger eddies in the Lofoten Basin compared with Svinoy (both theory and model) SVINOYSOUTHEAST LOFOTENNORTHEAST LOFOTEN α1.71 x 10 -2 5.37 x 10 -2 1.60 x 10 -2 T131764 U shear 0.63 0.83 g’4.8 10 -3 3.8 10 -3 2.9 10 -3 ____ Northeast Lofoten Southeast Lofoten Svinoy Stability analysis

11. FAMOS meeting - October 24-26, 2012

12. Sesonal variability of the eddy activity in the Lofoten Basin EKE (cm 2 s -2 ) Winter (JFM) Summer (JAS)

13. Eddy heat fluxes Depth-integrated convergence, winter FAMOS meeting - October 24- 26, 2012

14. SVINOY Southeast LOFOTEN Lateral eddy flux : 15 TW Surface flux : 9 TW Lateral eddy flux : 3.5 TW Surface flux : 5.5 TW

15. FAMOS meeting - October 24-26, 2012 Summary Model results are consistent with earlier studies using observations (surface drifters, e.g. Poulain et al., 1996, Jakobsen et al., 2003, Koszalka et al., 2011 or subsurface floats, Gascard et al., 2008, Rossby et al. 2009) and model simulations (e.g. Isachsen et al., 2012).  significant eddy activity in the NAwC (perturbation velocities reaching up to 20 cm s -1 in the slope current). Typical eddy scales (L=20-30 km, T=1-10 months) are consistent with theoretical estimates based on an idealized unstable baroclinic flow over sloping topography Model suggests that, in the southern Norwegian Sea, about 2/3 of the NAwC heat sink in winter is accounted for by eddy heat fluxes. Model dynamics should be further investigated to understand why eddy fluxes remain confined to the boundary of the basins, with limited heat transfer to the basin interiors. Evidence of a seasonal contrast the eddy field (amplitude but also shift in the location of most intense eddy activity in the Lofoten Basin) Model as well as observations suggest year-to-year variability of the mean flow : what is possibly the impact on the eddy field ?