Sub-decadal oceanic oscillations regulate the north-eastern Atlantic shelf ecosystems

Hjálmar Hátún, Payne, M., Sandø, A. and others...

Santander, 2011

Blue whiting

Sub-decadal oceanic oscillations and blue whiting recruitment

Outline

• The subpolar gyre – marine climate link and blue whiting stock dynamics

• Can we predict recruitment? – some new ideas on the sub-decadal variability.

SubtropicalGyre

SubpolarGyre

Labrador Sea convection

(Hatun et al., Science 2005)

1. The Subpolar Gyre and the marine climate

R

I

Salinity in the Irminger Current (obs.)

Salinity at Rockall (obs.)

Gyre index (GI)

Record high T and S

1. The Subpolar Gyre and the marine climate

Weak.

Strong

Simulated temperatureCold Warm

1. The Subpolar Gyre and the marine climate

Large mid-1990s changes!

Blue whiting

Blue whiting: Spawning-feeding distributions/migrations

Feeding

Spawning

Mackerel

Herring

Stor endringer i kolmule bestanden

Largest fishery in the North Atlantic!

A threefold blue whiting stock size increase

SST (in Rockall Areal)

Stock size (<- shifted 3 years)

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

Spatial Shift (Blue whiting catches – all nations)

1997

Spawning distribution: (Hátún et al. 2009, CJFAS)

Post-spawning migration: (Hátún et al. 2009, PIO)

So what about blue whiting recruitment?

Need to understand the processes

(Payne et al., 2011, In Press)

North AtlanticSub-polar gyre

Recruitment

Gyre index and recruitmentnot significantly correlated

Atmosphericforcing

Wind stress curl

-5

-3

-1

1

3

5x 10

-7

-50 -40 -30 -20 -10 040

45

50

55

60

65

UK

Green-land

Anticyclonic (Curl <0)

Wind stress (ws) - arrows (NCAR/NCEP)

Curl (ws) [N/m ]

2

0

Cyclonic (Curl >0)

2. Atmosphere-gyre details

WSC = 0

SubtropicalGyre

SubpolarGyre

2. Atmosphere-gyre details

SubpolarGyre

”Inter-gyreregion”

’Window’

2. Atmosphere-gyre details

WSC = 0

SubtropicalGyre

’Navidad’

”Inter-gyreregion”

SubpolarGyre

2. Atmosphere-gyre details

Recruitment and wind stress curl

2. Recruitment

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0.55

0.6

-30 -25 -20 -15 -10 -5 040

45

50

55

60

65

Spain

R

1980 1985 1990 1995 2000 2005 20100

1

2

3

4

5

6x 10

4

BW

Recru

itm

ent

Recruitment

Vs.

-5

-3

-1

1

3

5x 10

-7

-50 -40 -30 -20 -10 040

45

50

55

60

65

WSC

Recruitment and wind stress curl

1980 1985 1990 1995 2000 2005 2010-2

-1.5

-1

-0.5

0

0.5

1

1.5

2x 10

-7

Year

WS

C [

N/m

3]

Recruitment and wind stress curl

1980 1985 1990 1995 2000 2005 2010-2

-1.5

-1

-0.5

0

0.5

1

1.5

2x 10

-7

Year

WS

C [

N/m

3]

Nor

thw

ard

tran

spor

t

ImprovedRecruitment?

Sea surface heightand marine climate

Warmer

3. Monitoring with altimetry

Gyre Mode

Spatial pattern

(Updated from Hakkinen and Rhines, 2004)

3. Monitoring with altimetry

Time series(gyre index)

1994 1996 1998 2000 2002 2004 2006 2008 2010

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

Year

1992 1994 1996 1998 2000 2002 2004 2006 2008 2010-15

-10

-5

0

5

10

Year

dSS

H [

cm]

Transport anomalies of source waters

Western source

Eastern source

3. 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)

2. Hydrographic Pulses

35.1

35.15

35.2

35.25

35.3

35.35

35.4

35.45

35.5

Year

Dis

tanc

e [k

m]

1980 1985 1990 1995 2000 2005 20100

200

400

600

800

1000

1200

1400

1600

Porcupine

Shetland

Salinity @ 300m

2. Hydrographic Pulses Salinity

35.1

35.15

35.2

35.25

35.3

35.35

35.4

35.45

35.5

Year

Dis

tanc

e [k

m]

1980 1985 1990 1995 2000 2005 20100

200

400

600

800

1000

1200

1400

1600

Porcupine

Shetland

Salinity @ 300m

2. Hydrographic Pulses Salinity, currents

Wea

ker N

AC

35.1

35.15

35.2

35.25

35.3

35.35

35.4

35.45

35.5

Year

Dis

tanc

e [k

m]

1980 1985 1990 1995 2000 2005 20100

200

400

600

800

1000

1200

1400

1600

Porcupine

Shetland

Salinity @ 300m

2. Hydrographic Pulses

A new boom?

Salinity, currents and recruitment

So is the recruitment predictable?

Not with certainty -

But certainly not

if the marine climate is ignored

I ’predict’ that the 2009 year-class will be strong

1990 1995 2000 2005 2010

-6

-4

-2

0

2

4

6

8

10

12

14

Year

dS

SH

[cm

]

3. Monitoring with altimetryTransport anomalies

of source waters

1990 1995 2000 2005 2010

-6

-4

-2

0

2

4

6

8

10

12

14

Year

dS

SH

[cm

]

3. Monitoring with altimetryTransport anomalies

of source watersand blue whiting recruitment

Salt-pulses and blue whiting recruitment2. Recruitment

Porcupine

Shetland

So what about recruitment?

Bad recruitment Good recruitment

(Hátún et al., 2009, CJFAS)