1. CT1/CT3 Meeting 22-23 April 2013 Hamburg Predictability associated with the Atlantic ocean SST variability G. Gastineau, J. Garcia-Serrano, C. Frankignoul

2. Introduction Atlantic ocean SST variability : AMO + North Atlantic Horseshoe Are both pattern related? What are their influence on the European/American climate?

3. Data and methods Data : Atmosphere : 20CR-NOAA reanalysis (56 members) SST : HadISST Global warming influence removed : SST : Regression over the global mean SST time series removed Atmosphere : detrend

4. Global SST warming

5. Atlantic Multidecadal Oscillation AMO = low pass (10-yr) filtered North Atlantic SST AMO-proj = SST filtered with a ¼ ½ ¼ filtered projected onto AMO spatial pattern

6. Climatic impact of AMO

7. Maximum covariance analysis

8. North Atlantic Horseshoe Such mode is found in all ensemble members (at least for OND) PDF for NAH significance in OND SC R

9. Climate impact of NAH

10. Links horseshoe - AMO AMO-proj AMO-std

11. Non-stationarity Moving correlation between NAH and AMO using 20-yr window : Moving correlation between NAH and NAO in NDJ using 20-yr window :

12. Ongoing work Remove remote influence of Indo-Pacific variability Explain the non-stationary in the AMO-NAH links Compare the relative influence of SST to that of snow cover and sea ice cover. Focus also on the summer impacts of AMO

13. The research leading to these results has received funding from the European Union 7th Framework Programme (FP7 2007-2013), under grant agreement n.308299 NACLIM www.naclim.eu