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

Sea surface height and marine climate Warmer Monitoring with altimetry

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

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

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

Porcupine Shetland 300m Hydrographic Pulses Salinity

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

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

Porcupine Shetland 300m Hydrographic Pulses Salinity, currents Weaker NAC

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

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

Statements by Herbaut and Houssais (2009):...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....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.

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

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

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

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

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

The research leading to these results has received funding from the European Union 7th Framework Programme (FP ), under grant agreement n NACLIM

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

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

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

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

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

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

The research leading to these results has received funding from the European Union 7th Framework Programme (FP ), under grant agreements n NACLIM