Spatio-temporal variability and air-sea exchanges of carbon dioxide in three European ecosystems

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Spatio-temporal variability and air-sea

exchanges of carbon dioxide in three European

coastal environments

Alberto Borges & Michel Frankignoulle

University of Liège

Chemical Oceanography Unit

http://ulg.ac.be/oceanbio/co2

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2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 longitude (°E) 51.1 51.2 51.3 51.4 51.5 51.6 51.7 51.8 la ti tu d e ( °N ) Zeebrugge

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2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 longitude (°E) 51.1 51.2 51.3 51.4 51.5 51.6 51.7 51.8 la ti tu d e ( °N ) Zeebrugge

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2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 longitude (°E) 51.1 51.2 51.3 51.4 51.5 51.6 51.7 51.8 la ti tu d e ( °N ) 29.5 30.0 30.5 31.0 31.5 32.0 32.5 33.0 33.5 34.0 34.5 35.0 35.5

Salinity 10-21 march 97

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Partial pressure of CO

₂

(pCO

₂

)

10-21 march 97

2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 Longitude (°E) 51.1 51.2 51.3 51.4 51.5 51.6 51.7 51.8 la ti tu d e ( °N ) 180 220 260 300 340 380 420 460 500 540 580

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2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 longitude (°E) 15-26 February 99 51.1 51.2 51.3 51.4 51.5 51.6 51.7 51.8 la ti tu d e ( °N ) 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 longitude (°E) 03-12 May 99 51.1 51.2 51.3 51.4 51.5 51.6 51.7 51.8 la ti tu d e ( °N ) 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 longitude (°E) 20-28 August 97 51.1 51.2 51.3 51.4 51.5 51.6 51.7 51.8 la ti tu d e ( °N ) 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 longitude (°E) 20-30 October 97 51.1 51.2 51.3 51.4 51.5 51.6 51.7 51.8 la ti tu d e ( °N ) 60 110 160 210 260 310 360 410 460 510 560 610 660

Winter

Summer

Spring

Fall

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pCO₂ Zeebrugge Station 0 1 2 3 4 5 6 7 8 9 10 11 12 50 150 250 350 450 550 650 750

months of the year

µ a tm chlorophyll a 0 1 2 3 4 5 6 7 8 9 10 11 12 0 5 10 15 20 25

months of the year

µ

g

l

-1

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Annually integrated flux: + 4.5 mmol m-2 _day-1 _{(exchange coeff. Wanninkhof 1992)}

Surface of the Scheldt plume: 2100 km2

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Annually integrated flux: + 4.5 mmol m-2 _day-1 _{(exchange coeff. Wanninkhof 1992)}

Surface of the Scheldt plume: 2100 km2

Annual emission of CO₂: 112 tC day-1 ₌ _26%

Of the inner Scheldt estuary characterised by:

Flux = + 173 mmol m-2 _day-1 ₌ _{456 tC day}-1

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Provisional C budget for the Scheldt plume

(tC day

-1

₎

Inputs

CO

₂

from the Scheldt

34

a

Organic C from the Scheldt

16

b

_{- 52}

c

Organic C from the coast

47

c

Outputs

Organic carbon preservation in sediments

62

c

CO

₂

emission

112

a

Sum

97 - 133 175

a _{Borges & Frankignoulle (2002)} b _{Soetaert & Herman (1995)} c _{Wollast (1976; 1983)}

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pCO₂ English Channel -6 -4 -2 0 2 250 300 350 400 450 500 Fall (September 95) Summer (July 98) Spring (May 97) Winter (March 95) longitude (°E) µ a tm O₂ saturation -6 -4 -2 0 2 85 95 105 115 125 longitude (°E) %

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pCO₂ English Channel (1993-1999) 0 1 2 3 4 5 6 7 8 9 10 11 12 300 350 400 450

month of the year

µ a tm O₂ saturation 0 1 2 3 4 5 6 7 8 9 10 11 12 90 95 100 105 110

month of the year

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Annually integrated pCO2 ≈≈≈≈ 0

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Annually integrated CO₂ _{air-sea flux ≈}_≈_≈_{≈ 0} Why?

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New primary production = 1.0 mmolC m-2 _day-1 (15_{N incubations from L’Helguen et al. (1996))}

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9 mmolC m-2 _day-1 _{Continental shelf average}

5 mmolC m-2 _day-1 _{Southern Bight of the North Sea} 7 mmolC m-2 _day-1 _{Gulf of Biscay}

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Benthic calcification in Eastern Channel = 19 mmolCaCO₃ m-2 _day-1

Release of CO₂ = +13 mmolC m-2 _day-1

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Benthic calcification in Eastern Channel = 19 mmolCaCO₃ m-2 _day-1

Release of CO₂ = +13 mmolC m-2 _day-1

Area 5400 km2

Whole of Channel

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Galician coast

temperature (°C) 27 June - 7 July 98

-10.3 -10.1 -9.9 -9.7 -9.5 -9.3 -9.1 -8.9 -8.7 Longitude (°E) 42.1 42.2 42.3 42.4 42.5 42.6 42.7 42.8 42.9 43.0 43.1 43.2 L a ti tu d e ( °N ) 13.0 13.5 14.0 14.5 15.0 15.5 16.0 16.5 17.0 17.5 18.0 18.5 19.0 19.5 20.0 20.5 21.0 21.5

Cap Finisterre

Rias

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265 275 285 295 305 315 325 335 345 355 365 375 385 395 405 415 -10.3 -10.1 -9.9 -9.7 -9.5 -9.3 -9.1 -8.9 -8.7 Longitude (°E) 42.1 42.2 42.3 42.4 42.5 42.6 42.7 42.8 42.9 43.0 43.1 43.2 L a ti tu d e ( °N )

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temperature (°C) 6 - 16 January 98

-10.8-10.6-10.4-10.2-10.0 -9.8 -9.6 -9.4 -9.2 -9.0 -8.8 -8.6 Longitude (°E) 41.2 41.4 41.6 41.8 42.0 42.2 42.4 42.6 42.8 43.0 43.2 43.4 L a ti tu d e ( °N ) 13.7 13.8 13.9 14.0 14.1 14.2 14.3 14.4 14.5 14.6 14.7 14.8 14.9 15.0 15.1 15.2 15.3 15.4 15.5 15.6 15.7 15.8 15.9 16.0

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temperature (°C) 6 - 16 January 98

-10.8-10.6-10.4-10.2-10.0 -9.8 -9.6 -9.4 -9.2 -9.0 -8.8 -8.6 Longitude (°E) 41.2 41.4 41.6 41.8 42.0 42.2 42.4 42.6 42.8 43.0 43.2 43.4 L a ti tu d e ( °N ) 13.7 13.8 13.9 14.0 14.1 14.2 14.3 14.4 14.5 14.6 14.7 14.8 14.9 15.0 15.1 15.2 15.3 15.4 15.5 15.6 15.7 15.8 15.9 16.0

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pCO

₂

(µatm) 6 - 16 January 98

-10.8-10.6-10.4-10.2-10.0 -9.8 -9.6 -9.4 -9.2 -9.0 -8.8 -8.6 Longitude (°E) 41.2 41.4 41.6 41.8 42.0 42.2 42.4 42.6 42.8 43.0 43.2 43.4 L a ti tu d e ( °N ) 310 315 320 325 330 335 340 345 350

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Annual integration of the air-sea CO₂ fluxes: June/July 97

june/july 98 upwelling season

August 98 September 99

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January 98 downwelling season

Upwelling season = March to October = 6 months Continental shelf:

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January 98 downwelling season

Upwelling season = March to October = 6 months Continental shelf:

- 6.1 mmol m-2 _day-1 _{(exchange coeff. Wanninkhof 1992)}

Off-shore region: - 4.4 mmol m-2 _day-1

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Summary of CO

₂

atmospheric fluxes

mmolC m

-2

_day

-1 surface area of continental shelves (based on Walsh, 1988) 0° - 30° 30° - 60° 60°- 90° 0 25 50 75 100 28% 58% 14% Latitude % surface area of continental shelves (based on Walsh, 1988) 0° - 30° 30° - 60° 60° - 90° 0 25 50 75 100 Northern Hemisphere Southern Hemisphere 14 % 14 % 50 % 8 % 13 % 1 % Latitude %

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