A trans-Atlantic linkage - between the Newfoundland and Rockall basins

1. -3 Chl [mg m ] SeaWiFS-based chlorophyll in selekt Blue whiting A trans-Atlantic linkage-between the Newfoundland and Rockall basins Hjálmar Hátún, and Annebritt Sandø EGU, 2013

2. Monitoring with altimetry Sea surface heightand marine climate Warmer

3. Monitoring with altimetry Gyre Mode Time series (gyre index) Spatial pattern (Updated from Hakkinen and Rhines, 2004)

4. Monitoring with altimetry Transport anomalies of source waters Eastern source ~ 7 Sv (Pingree, 2002) Western source

5. Hydrographic Pulses Decompose onto a S-axis An along-Continental Slope perspective (Data availability) Shetland Porcupine (Hátún et al. 2009, CJFAS)

6. Hydrographic Pulses Salinity Salinity @ 300m Shetland Porcupine

7. Hydrographic Pulses Salinity, currents Salinity @ 300m Shetland NAC index Weaker Porcupine

8. Herring Mackerel Blue whiting Recruitment Feeding Post-spawning migration (Hátún et al., 2009, PIO) Blue whiting ? Spawning distribution (Hátún et al., 2009, CJFAS)

9. Hydrographic Pulses Salinity, currents Salinity @ 300m Shetland Weaker NAC Porcupine

10. Hydrographic Pulses Salinity, currents and recruitment Salinity @ 300m Shetland A new boom? (’prediction’ made at the ICES decadal symposium in 2011) Porcupine

11. (Bersch et al. 2007): ’...shift in subarctic surface and intermediate water masses between the West European Basins (/Iceland Basin) and the Newfoundland Basin’ Iceland Basin NF Basin A link to the Newfoundland Basin Strong gyre Weak gyre (Hátún, et al., 2005)

12. Statements by Herbaut and Houssais (2009): ...contrary to the suggestion of Hátún et al. (2005) and Bersch et al. (2007), this acceleration of the gyre does not force the changes in the eastern North Atlantic. ...salinity changes in the eastern SPG are mostly due to the set-up of an ‘‘intergyre gyre’’ in response to the wind-stress anomalies rather than to an enhancement of the gyre circulation due to the buoyancy flux.

13. The ’Inter-gyre’ gyre(simulated stream-function) (Eden and Willebrand, 2001) NAO low Sub-arctic front NAO high

14. N NAC Depth (m) NAC shifts in the Newfoundland Basin Subarctic water Simulated salinity (MICOM, upper layers)

15. NAC shifts in the Newfoundland Basin First EOF (after linear detrending)

16. Rockall Simulated Transport PC NAC position and western water influx Covariance betwen the NAC position and the influx of western water north Wind stress curl (Herbaut and Houssais, 2009) No Yes NF Basin south

17. Messages • Recruitment of blue whiting is linked to: • Sub-decadal hydrographic pulses • And/ or the strength of the North Atlantic Current • The position of the sub-arctic front in the Newfoundland Basin - a critical metric • The mid-1990s change was an oceanic reorganization

18. 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

19. Atmospheric forcing - wind stress curl WSC (shifted 2 years ->) (42-48N, 28-38W) NAC position

20. Atmospheric forcing – heat loss ...can drive the sub-decadal variability, but not the rapid mid-1990s change

21. Streamf.(1996-2003) minus Streamf. (1989-1995) Dual SPG states – divided by Rockall Sv NAC The dramatic mid-1990s change, an internal oceanic change Difference

22. Simulated transport Western and Eastern water contribution – on sub-decadal scales

23. Western and Eastern water contribution – on sub-decadal scales Shetland Porcupine

24. Eastern water -saline pulses Simulated salinity anomaly (time-lat. plot)

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