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

Hjálmar Hátún, and Annebritt Sandø

EGU, 2013

Blue whiting

Sea surface heightand marine climate

Warmer

Monitoring with altimetry

Gyre Mode

Spatial pattern

(Updated from Hakkinen and Rhines, 2004)

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

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

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

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

Hydrographic Pulses Salinity, currents

Wea

kerNAC index

Blue whiting

Blue whiting

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

Mackerel

Herring

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

1980 1985 1990 1995 2000 2005 20100

1

2

3

4

5

6x 10

4

BW

Recru

itm

ent

Recruitment ?

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

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

Hydrographic Pulses

A new boom?(’prediction’ made at the

ICES decadal symposium in 2011)

Salinity, currents and recruitment

40W 30W 20W 10W

45

50

55

60

65

40W 30W 20W 10W45N

50N

55N

60N

65NIceland

Scot-land

1993

S > 35.35S 35.35S > 35.10S 35.10

<

<

1998

<

Strong gyre Weak 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

IcelandBasin

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

34

34.2

34.4

34.6

34.8

35

35.2

35.4

1973

-60 -50 -40 -30 -20 -10 040

45

50

55

60

65

Subarctic water

0 5 10 15 20 25 30 35 40 45-5000

-4500

-4000

-3500

-3000

-2500

-2000

-1500

-1000

-500

020

Dep

th (m

)

N

NAC shifts in the Newfoundland Basin

Simulated salinity(MICOM, upper layers)

NAC

-0.03

-0.01

0.01

0.03

0.05

0.07

-60 -50 -40 -30 -20 -10 040

45

50

55

60

65

NAC shifts in the Newfoundland Basin

First EOF (after linear detrending)

NAC position and western water influx

-0.03

-0.01

0.01

0.03

0.05

0.07

-60 -50 -40 -30 -20 -10 040

45

50

55

60

65

1960 1965 1970 1975 1980 1985 1990 1995 2000 20050

1

2

3

4

5

6

7

Tra

nspo

rt [

Sv]

Year

PCNF Basin

40W 30W 20W 10W

45

50

55

60

65

40W 30W 20W 10W45N

50N

55N

60N

65NIceland

Scot-land

1993

S > 35.35S 35.35S > 35.10S 35.10

<

<

1998

<

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 (FP7 2007-2013), under grant agreement n.308299NACLIM www.naclim.eu

1960 1965 1970 1975 1980 1985 1990 1995 2000 20050

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

Win

d S

tres

s C

url x

1e-

6

Year

WSC (shifted 2 years ->)(42-48N, 28-38W)

NACposition

Atmospheric forcing - wind stress curl

1950 1960 1970 1980 1990 2000 2010-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

Atmospheric forcing – heat loss

...can drive the sub-decadal variability,but not the rapid mid-1990s change

-0.6

-0.5

-0.4

-0.3

-0.2

0.2

0.3

0.4

0.5

0.6

-70 -60 -50 -40 -30 -20 -10 020

25

30

35

40

45

50

55

60

65

-6

-4

-2

0

2

4

6

-60 -50 -40 -30 -20 -10 040

45

50

55

60

65

1970 1980 1990 2000

-0.3

-0.2

-0.1

0

0.1

0.2

Year

NA

C p

ositi

on

NAC

Difference

Streamf.(1996-2003) minus Streamf. (1989-1995) 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

40W 30W 20W 10W

45

50

55

60

65

40W 30W 20W 10W45N

50N

55N

60N

65NIceland

Scot-land

1993

S > 35.35S 35.35S > 35.10S 35.10

<

<

1998

<

1960 1965 1970 1975 1980 1985 1990 1995 2000 20050

1

2

3

4

5

6

7

Tra

nspo

rt [

Sv]

Year

Simulated transport

1960 1965 1970 1975 1980 1985 1990 1995 2000 20050

1

2

3

4

5

6

7

Tra

nspo

rt [

Sv]

Year1960 1965 1970 1975 1980 1985 1990 1995 2000 20050

1

2

3

4

5

6

7

Tra

nspo

rt [

Sv]

Year

40W 30W 20W 10W

45

50

55

60

65

40W 30W 20W 10W45N

50N

55N

60N

65NIceland

Scot-land

1993

S > 35.35S 35.35S > 35.10S 35.10

<

<

1998

<

Western and Eastern water contribution – on sub-decadal scales

Porcupine

Shetland

Eastern water -saline pulses

Simulatedsalinity anomaly(time-lat. plot)

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