Download Dynamics of the Subarctic Gyre and physical/biological interactions

Dynamics of the Subarctic Gyre and physical/biological
interactions
Svein Sundby
EUR-OCEANS BASIN Workshop, Reykjavík, 12 – 14 March 2005
Outline
• Regime shifts and hypothesis of advection of Calanus as the
link between temperature and cod recruitment (Sundby 2000)
• New interpretations on the GSAs (Sundby and Drinkwater 2005)
- implications for advection
• Some very preliminary results on abundance of Calanus
finmarchicus in the North Sea and water masses in the
Norwegian Trench.
Ecosystem responses to climate change
Linear response
Non-linear respons 1
Non-linear respons 2
Ottersen et al. (2004)
Calanus finmarchicus in relation to the circulation of the Subartic Gyre
Sundby (2000)
Gjevik et al. (1995)
Mean ambient temperature for Calanus finmarchicus
population in the North Atlantic (hibernation excluded).
Sundby (2000)
Recruitment in Atlantic cod
Temperature
for optimal
growth rate
Planque and Frédou (1999)
Sundby (2000)
Rothschild (1998)
Calanus finmarchicus in relation to the circulation of the Subartic Gyre
Sundby (2000)
ATLANTIC COD RECRUITMENT
Temperature
Cod recruitment
ADVECTION
Calanus finmarchicus
Cod recruitment
Principal spatial features of Calanus finmarchicus, cod and temperature in
the North Atlantic
Sundby (2000)
Conceptual model for the combined advection of heat and Calanus
finmarchicus from the deep-sea core production region onto the
surrounding shelves with cod populations
Change in advection
along a positive
temperature gradient
Change in advection
along a negative
temperature gradient
Change in advection
along the isolines of
temperature
Sundby (2000)
Ecosystem responses to climate change
Linear response
Non-linear respons 1
Non-linear respons 2
Ottersen et al. (2004)
• Regime shifts and hypothesis of advection of Calanus as the
link between temperature and cod recruitment (Sundby 2000)
• New interpretations on the GSAs (Sundby and Drinkwater 2005)
- implications for advection
• Some very preliminary results on abundance of Calanus
finmarchicus in the North Sea and water masses in the
Norwegian Trench.
Dickson et al. (1988)
Belkin et al. (1998)
Low salinity anomaly induced by patch advection
V
S
t
V
S0
S1 S
2
S3
t
1970s
GSA
Dooley et al. (1984)
Low Salinity Anomalies
84
90
98
82
89
97
70s
80
95
Year
Year
74
86
94
93
72
85
70
84
91
68
83
90
66
92
89
82
2
4
6
8
10
12
0
2
Distance (1000 km)
4
6
8
10
0
12
2
High Salinity Anomalies
70
85
69
68
84
67
83
66
65
60s
64
82
80s
81
63
80
62
79
61
0
2
4
6
8
Distance (1000 km)
10
12
0
2
4
4
6
8
Distance (1000 km)
Distance (1000 km)
Year
0
90s
96
87
76
Year
Year
80s
88
78
6
8
Distance (1000 km)
10
12
10
12
Temperature in Kola Section
and Inverted Ice Index in Davis Strait
5
Annual Mean
4
Davis Strait
3
Kola Section
2
1950
1960
1970
1980
1990
2000
5
Temperature / Inv. Ice Index
Temperature/Inv. Ice Index
6
3-yrs
Run. Mean
4
3
Davis Strait
Kola Section
2
1950
1960
1970
1980
1990
2000
Salinity in
the Subpolar
Gyre
Kola
Fylla
Rockall
Newfoundland
u . S = K 2S
S/t = u . S - K 2S > 0
Low salinity anomaly induced by patch advection
V
S
t
V
S0
S1 S
2
S3
t
Low salinity anomaly induced by flux variation
in a salinity gradient
v
S
t
V
S3 S2 S1 S0
t
High and Low Salinity Anomalies of the Subarctic Gyre
Propagation speed from region A to region B
(cm/s)
5
1960/70s GSA in the
Northwest Atlantic
4
3
A high salinity
anomaly in the
Northwest
Atlantic
2
A high salinity
anomaly of the
Northeast
Atlantic
Mid 70s GSA
in the
Northeast
Atlantic
1
0
0
1
2
3
4
Propagation speed from region C to region D (cm/s)
5
20
10
0
-10
-20
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
1970
1980
1990
2000
Temperature Kola Section
Temperature
SLP Anomaly
NAO Winter Index
5
4
3
2
1900
1910
1920
1930
1940
1950
1960
Year
NAO and the Atlantic water temperature
in the Barents Sea
Climate Anomalies during the beginning of the 20th century
NORTHWEST ATLANTIC
NORTHEAST ATLANTIC
Fylla Bank (A) - Grand Bank (B)
Faroe-Shetland (C) - Kola Section (D)
Climate
Propagation
Climate
Propagation
PERIOD
Anomaly
Speed (cm/s) PERIOD
Anomaly
Speed (cm/s) 3-years mean
1904 - 06
No obs.
1904 - 06
HIGH
5,1
1,109
1908 - 12
No obs.
1908 - 12
LOW
1,9
0,636
1912 - 14
No obs.
1912 - 14
HIGH
3,8
0,585
Mean Speed/Mean NAO index
1,90
0,636
Mean Speed/Mean NAO index
4,45
0,847
NAO Index
Propagation speed of salinity anomalies in the
NE and NW Atlantic versus NAO Index
4,5
Propagation speed (cm/s)
4
3,5
3
2,5
2
1,5
1
R2 = 0,13
0,5
0
-2
-1
0
1
NAO Index 3-yrs mean
2
3
• Regime shifts and hypothesis of advection of Calanus as the
link between temperature and cod recruitment (Sundby 2000)
• New interpretations on the GSAs (Sundby and Drinkwater 2005)
- implications for advection
• Some very preliminary results on abundance of Calanus
finmarchicus in the North Sea and water masses in the
Norwegian Trench.
Calanus finmarchicus in relation to the circulation of the Subartic Gyre
Sundby (2000)
1973-99
Norwegian
Coastal
Current
Atlantic inflow
Norwegian Sea intermediate water
Feie - Shetland, 1970 -99, March and April
Blue: st.9-12, 100-200m. Red: st.4-8, 300m-bottom.
Atlantic
Water
10
AF
27.3
27
9
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Temperature (ITS-90)
8
7

27.5
27.7
6
5
NSIW
4
34.9
34.95
35
35.05
35.1
35.15
35.2
Salinity (PSU)
35.25
35.3
35.35
Norwegian Sea Intermediate Water
35.4
Mean abundance of C. finmarchicus at B1 vs the deep
water temperature in the Norwegian Trench
8,00
7,80
R2 = 0,27
Temperature
7,60
7,40
7,20
7,00
6,80
6,60
6,40
6,20
0
10
20
30
40
C. finmarchicus abundance
50