Blue whiting
A trans-Atlantic linkage
- between the Newfoundland and Rockall basins
Hjálmar Hátún,
and Annebritt Sandø
EGU, 2013
Monitoring with altimetry
Sea surface height
and marine climate
Warmer
Monitoring with altimetry
Gyre Mode
Time series
(gyre index)
Spatial pattern
0.5
0.4
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
1994
1996 1998
2000
2002
Year
2004
2006
2008
2010
(Updated from Hakkinen and Rhines, 2004)
Monitoring with altimetry
Transport anomalies
of source waters
10
Eastern source
~ 7 Sv
(Pingree,
2002)
dSSH [cm]
5
0
-5
-10
Western source
-15
1992
1994
1996
1998
2000
2002
Year
2004
2006
2008
2010
Hydrographic Pulses
(Data availability)
An along-Continental Slope
perspective
Decompose onto a S-axis
Shetland
Porcupine
(Hátún et al. 2009, CJFAS)
Hydrographic Pulses
Salinity
Salinity @ 300m
35.5
Shetland 1600
35.45
1400
35.4
Distance [km]
1200
35.35
1000
35.3
800
600
35.25
400
35.2
200
35.15
Porcupine
0
1980
1985
1990
1995
Year
2000
2005
2010
35.1
Hydrographic Pulses
Salinity, currents
Salinity @ 300m
NAC index
35.45
1400
35.4
Distance [km]
1200
35.35
1000
35.3
800
600
35.25
400
35.2
200
35.15
Porcupine
0
1980
1985
1990
1995
Year
2000
2005
2010
35.1
Weaker
35.5
Shetland 1600
Blue whiting
Herring
Feeding
Post-spawning migration
(Hátún et al., 2009, PIO)
4
6
x 10
5
Recruitment
Blue whiting
?
Mackerel
BW Recruitment
4
3
Spawning distribution
(Hátún et al., 2009, CJFAS)
2
1
0
1980
1985
1990
1995
2000
2005
2010
Hydrographic Pulses
Salinity, currents
Salinity @ 300m
35.45
1400
35.4
Distance [km]
1200
35.35
1000
35.3
800
600
35.25
400
35.2
200
35.15
Porcupine
0
1980
1985
1990
1995
Year
2000
2005
2010
35.1
Weaker NAC
35.5
Shetland 1600
Hydrographic Pulses
Salinity, currents and recruitment
Salinity @ 300m
35.5
Shetland 1600
1400
A new boom?
1200
(’prediction’ made 35.4
at the
ICES decadal symposium in 2011)
Distance [km]
35.45
35.35
1000
35.3
800
600
35.25
400
35.2
200
35.15
Porcupine
0
1980
1985
1990
1995
Year
2000
2005
2010
35.1
A link to the Newfoundland Basin
(Bersch et al. 2007):
’...shift in subarctic surface and intermediate water masses between the
West European Basins (/Iceland Basin) and the Newfoundland Basin’
65N
Iceland
Strong gyre
1993
65
60N
60
Iceland
Basin
55
55N
Scotland
50
1998
Weak gyre
S>
S<
S>
S<
35.35
35.35
35.10
35.10
45
<
50N
NF Basin
45N
40W
30W
20W
10W
40W
30W
20W
10W
(Hátún, et al., 2005)
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.
The ’Inter-gyre’ gyre
(simulated stream-function)
(Eden and Willebrand, 2001)
Sub-arctic front
NAO low
NAO high
NAC shifts in the Newfoundland Basin
20
0
1973
65
35.4
N
Depth (m)
-500
NAC
60
35.2
-1000
35
-1500
55
Subarctic water
34.8
-2000
50
34.6
-2500
34.4
45
-3000
34.2
Simulated salinity
-3500
40
-60
(MICOM, upper layers)
-50
-40
-30
-20
-10
0
34
NAC shifts in the Newfoundland Basin
65
0.07
First EOF (after linear detrending)
60
0.05
55
0.03
50
0.01
45
-0.01
40
-60
-50
-40
-30
-20
-10
0
-0.03
1998
NAC 1993
position and western
water influx
Covariance betwen the NAC position
Rockall
and the influx of western water
Iceland
Scotland
S > 35.35
S < 35.35
S > 35.10
S < 7 35.10
Simulated
6
Transport
north
5
10W
Wind stress curl
(Herbaut and Houssais, 2009)
40W
Transport [Sv]
20W
0.07
30W
4
20W
10W
No
0.05
3
0.03
2
Yes
0.01
1
NF Basin
0
1960
PC
-0.01
1965
1970
1975
1980
1985
Year
1990
1995
2000
2005
south
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.308299
NACLIM www.naclim.eu
Atmospheric forcing - wind stress curl
Wind Stress Curl x 1e-6
0.2
0.18
WSC (shifted 2 years ->)
0.16
(42-48N, 28-38W)
0.14
0.12
0.1
0.08
0.06
NAC
0.04
position
0.02
0
1960
1965
1970
1975
1980
1985
Year
1990
1995
2000
2005
65
60
55
Atmospheric forcing – heat loss
50
45
40
35
30
25
20
-70
-60
-50
-40
...can drive the sub-decadal variability,
but not the rapid mid-1990s change
0.4
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
1950
1960
1970
1980
1990
2000
2010
-30
-20
-10
0
Dual SPG states – divided by Rockall
Streamf.(1996-2003) minus Streamf. (1989-1995)
Sv
65
6
NAC position
0.2
0.1
0
4
60
NAC
-0.1
-0.2
2
-0.3
55
1970
1980 1990
Year
2000
0
50
-2
The dramatic mid-1990s
change, an internal oceanic change
45
-4
40
-60
Difference
-50
-40
-30
-20
-10
0
-6
Iceland
Western
and Eastern water
1993
1998 contribution –
on sub-decadal scales
7
Scotland
S>
S<
S>
S<
35.35
35.35
35.10
35.10
Simulated transport
6
20W
10W
Transport [Sv]
5
4
40W
30W
20W
10W
3
2
1
0
1960
1965
1970
1975
1980
1985
Year
1990
1995
2000
2005
Western
and Eastern water
contribution – on
1993
1998
Iceland
sub-decadal scales
Shetland
7
Scotland
6
Porcupine
35.35
35.35
35.10
35.10
5
10W
Transport [Sv]
20W
S>
S<
S>
S<
4
40W
30W
20W
10W
3
2
1
0
1960
1965
1970
1975
1980
1985
Year
1990
1995
2000
2005
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 (FP7 2007-2013),
under grant agreements n.308299 NACLIM
www.naclim.eu