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.
Linear response Non-linear respons 1 Non-linear respons 2
Ottersen et al. (2004)
Ecosystem responses to climate change
Sundby (2000)
Calanus finmarchicus in relation to the circulation of the Subartic Gyre
Gjevik et al. (1995)
Sundby (2000)
Mean ambient temperature for Calanus finmarchicus population in the North Atlantic (hibernation excluded).
Planque and Frédou (1999)
Recruitment in Atlantic cod
Temperature for optimal growth rate
Sundby (2000)
Rothschild (1998)
Sundby (2000)
Calanus finmarchicus in relation to the circulation of the Subartic Gyre
Temperature Cod recruitment
Calanus finmarchicus Cod recruitment
ADVECTION
ATLANTIC 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
Sundby (2000)
Change in advection along a negative
temperature gradient
Change in advection along the isolines of
temperature
Change in advection along a positive
temperature gradient
Linear response Non-linear respons 1 Non-linear respons 2
Ottersen et al. (2004)
Ecosystem responses to climate change
• 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)
S 2
S 0 S 1S 3
tt
SV
V
Low salin ity anom aly induced by patch advection
Dooley et al. (1984)
1970s GSA
66
68
70
72
74
76
78
80
82
84
0 2 4 6 8 10 12
Distance (1000 km)
Ye
ar
82
83
84
85
86
87
88
89
90
0 2 4 6 8 10 12
Distance (1000 km)
Yea
r
89
90
91
92
93
94
95
96
97
98
0 2 4 6 8 10 12
Distance (1000 km)
Yea
r61
62
63
64
65
66
67
68
69
70
0 2 4 6 8 10 12
Distance (1000 km)
Yea
r
79
80
81
82
83
84
85
0 2 4 6 8 10 12
Distance (1000 km)
Yea
r
Low Salinity Anomalies
70s 80s 90s
High Salinity Anomalies
60s 80s
2
3
4
5
6
1950 1960 1970 1980 1990 2000
Te
mp
era
ture
/In
v.
Ice
In
de
x
Davis Strait
Kola Section
2
3
4
5
1950 1960 1970 1980 1990 2000
Tem
per
atu
re /
In
v. I
ce I
nd
ex
Davis Strait
Kola Section
Temperature in Kola Section and Inverted Ice Index in Davis Strait
Annual Mean
3-yrs Run. Mean
Kola
Rockall
Fylla
Newfoundland
Salinity in the Subpolar Gyre
u . S = K 2S
S/t = u . S - K 2S > 0
S 2
S 0 S 1S 3
tt
SV
V
Low salin ity anom aly induced by patch advection
S 2 S 0S 1S 3
tV
t
Sv
Low salin ity anom aly induced by flux variationin a salin ity gradient
NORTHWEST ATLANTIC NORTHEAST ATLANTIC
Fylla Bank (A) - Grand Bank (B) Faroe-Shetland (C) - Kola Section (D)
Salinity Propagation Salinity Propagation NAO Index
PERIOD Anomaly Speed (cm/s) PERIOD Anomaly Speed (cm/s) 3-years mean
47 - 50 High 2,3 No clear signal -0,200
No clear signal 53 - 55,8 High 2,52 0,207
No clear signal 55 -59,2 Low 1,68 -0,496
57,5 - 60 Low 2,82 59 - 61,2 High 3,2 -0,020
61 - 65 High 1,76 63 - 66,4 Low 2,07 -1,607
69 - 71 Low 3,52 68 - 70,3 High 3,06 -0,845
77 - 80,5 High 2,01 76 - 79,8 Low 1,85 -0,767
82 - 84 Low 3,52 82 - 83,8 High 3,91 1,140
87 - 89 High 3,52 87 - 89,4 Low 2,94 -0,160
89,5 - 92,5 Low 2,35 90-93,1 High 2,27 1,831
No clear signal 93-98 Low 1,76 -0,004
No clear signal 98 - 00,0 High 3,52 0,949
Mean Speed/Mean NAO index 2,40 2,06 -0,539
Mean Speed/Mean NAO index 3,05 3,08 0,544
Sal ini ty fl ux events of the Subarctic Gyre 1947-1990
02
1
E vent No.
NE Atlantic
NW Atlantic
Low fl ux events of the Subarcti c Gyre 1947-1990
-4
6
1
E vent Number
High fl ux events of the Subarctic Gyre 1947-1990
02
1
E vent Number
P r opagat ion speeds of high an d low S alin it y A n omalies of t he S ubpolar Gyr e
1
2
1 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8 1,9 2
P ro p a g a tio n sp e e d fro m R e g io n C to R e g io n D (c m/s)
P r opagati on s peeds of hi gh and l ow s al i ni ty anomal i es
012345
0 0, 1 0, 2 0, 3 0, 4 0, 5 0, 6 0, 7 0, 8 0, 9 1
P r opagat ion s speeds in Nor t heast A t lan t ic ( cm/ s)
High and Low Salinity Anomalies of the Subarctic Gyre
0
1
2
3
4
5
0 1 2 3 4 5
Propagation speed from region C to region D (cm/s)
Pro
pa
ga
tio
n s
pe
ed
fro
m r
eg
ion
A t
o r
eg
ion
B
(cm
/s)
1960/70s GSA in the Northwest Atlantic
Mid 70s GSA in the
Northeast Atlantic
A high salinity anomaly of the
Northeast Atlantic
A high salinity anomaly in the
Northwest Atlantic
NAO Winter Index
-20
-10
0
10
20
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
SL
P A
no
mal
y
Temperature Kola Section
2
3
4
5
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
Year
Tem
per
atu
re
NAO and the Atlantic water temperature in the Barents Sea
NORTHWEST ATLANTIC NORTHEAST ATLANTIC
Fylla Bank (A) - Grand Bank (B) Faroe-Shetland (C) - Kola Section (D)
Climate Propagation Climate Propagation NAO Index
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
Climate Anomalies during the beginning of the 20th century
Propagation speed of salinity anomalies in the NE and NW Atlantic versus NAO Index
0
0,5
1
1,5
2
2,5
3
3,5
4
4,5
-2 -1 0 1 2 3
NAO Index 3-yrs mean
Pro
pag
atio
n s
pee
d (
cm/s
)
R2 = 0,13
• 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.
Sundby (2000)
Calanus finmarchicus in relation to the circulation of the Subartic Gyre
1973-99
Atlantic inflow
Norwegian Sea intermediate water
Norwegian Coastal Current
34.9 34.95 35 35.05 35.1 35.15 35.2 35.25 35.3 35.35 35.44
5
6
7
8
9
10
Salinity (PSU)
Tem
pera
ture
(IT
S-9
0)27
27.3
27.5 27.7
Feie - Shetland, 1970 -99, March and AprilBlue: st.9-12, 100-200m. Red: st.4-8, 300m-bottom.
NSIW
AF
Norwegian Sea Intermediate Water
Atlantic Water
6,20
6,40
6,60
6,80
7,00
7,20
7,40
7,60
7,80
8,00
0 10 20 30 40 50
C. finmarchicus abundance
Te
mp
era
ture
R2 = 0,27
Mean abundance of C. finmarchicus at B1 vs the deep water temperature in the Norwegian Trench