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