Trans-Atlantic Linkages- via the subpolar gyre

Hjálmar Hátún

SeaWiFS-based chlorophyll in selekt

Chl [mg m-3

]

0.01

0.1

1

10

ASOF - Halifax - 08

Co-authors: M. R. Payne, G, Beaugrand, P. C. Reid, A. Sandø, H. Drange, B. Hansen, J. A. Jacobsen, D. Bloch

Rockall

IrmingerCurrent

Faroe Current

(Hatun et al., Science 2005)

The Subpolare Gyre and the marine climate

RI

Irminger Current (obs.)

Rockall (obs.)

Gyre index

Record high T and S

The Subpolare Gyre and the marine climate

2.The Subpolar Gyre andPlankton

Continuous Plankton Recorder (CPR) (SAHFOS, Plymouth)

Towing lines since the 1940s

Area south of Iceland

SSH (temperature og currents)Hátún et al., Science, 2005

Phytoplankton

Sea Surface TemperatureBeaugrand, Science 2002

Calanus finmarchicus

”Gyre pattern”

2. SPG and planktonPhytoplankton

Time-development of the ”gyre-mode”

SSH

PCI

SST

Calanus finmarchicus

SST

2. SPG and plankton

Less

Cal

. F

in.

Amount of zooplankton with relatively warm water affinities

(boreal)

CTA: Cold-Temperate Assemblagecalanoid copepods Aetidus armatus, Pleuromamma robusta, Acartia spp. and Metridia lucens.

2. SPG and planktonZooplankton

3.The Subpolar Gyre andPelagic Fish (blue whiting)

Stor endringer i kolmule bestanden

Largest fishery in the North Atlantic!

3. SPG and blue whiting

Large mid-1990s increase

Warm (1998-2003)Cold (1990-1996)

Spatial Shift(Catches – all nations)

1997

3. SPG and blue whiting

Western region

East-West index = (Faroese landings from western region)/

(total faroese landigs)

Blue whiting migration

Western index Gyre index

Pilot whale migration

Pilot whale migration

(Catch in NE area)/(total catch)

Long-term pilot whale migration

Prediction

Reversal in 2005-2006!

Is this causing the poorrecruitments during 05-06?

Good recruitment conditionsshould resume

Atmospheric forcing

• Katja Lohmann, Helge Drange and Mats Bentsen: What caused the strong weakening of the North Atlantic subpolar gyre post 1995?, Submitted. for GRL

0-wind stress curl