Atmospheric CO2 exchanges over the European Continental shelf

(1)

Atmospheric CO

₂

exchanges over the

European Continental Shelf

Alberto Borges & Michel Frankignoulle

University of Liège

Chemical Oceanography Unit

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

(2)

(3)

pCO

₂

in the Scheldt estuary

Biogest cruises

0 5 10 15 20 25 30 0 2000 4000 6000 8000 Winter (december 96) Spring (may 98) Summer (july 96) Fall (october 98) salinity µ a tm

(4)

O

₂

saturation level

in the Scheldt estuary

Biogest cruises

0 5 10 15 20 25 30 0 20 40 60 80 100 Winter (december 96) Spring (may 98) Summer (july 96) Fall (october 98) salinity %

(5)

Total organic carbon

in the Scheldt estuary

Biogest cruises

0 5 10 15 20 25 30 0 5000 10000 15000 Winter (december 96) Spring (may 98) Summer (july 96) Fall (october 98) salinity µ m o l k g -1

(6)

CO

₂

atmospheric fluxes

in the Scheldt estuary

Biogest cruises

0 5 10 15 20 25 30 0 500 1000 1500 2000 Winter (december 96) Spring (mai 98) Summer (july 96) Fall (october 98) salinity m m o l m -2 d a y -1

(7)

470 tons of C per day

net emission of CO

₂

from the Scheldt estuary

historical data-set

0 1 2 3 4 5 6 7 8 9 10 11 12 0 200 400 600 800

months of the year

to n s o f C d a y -1

(8)

CO

₂

emission by the Biogest estuaries

tons of C per day

(9)

(10)

Surface area in Europe of salinity < 34

111 200 km²

(11)

emission of CO

₂

by

European estuaries

0

20

40

60

80

0

25

50

75 % surface of internal estuaries

m

il

li

o

n

t

o

n

s

C

y

e

a

r

-1

(12)

emission of CO

₂

by

European estuaries

0

20

40

60

80

0

25

50

75

0

3

6

9

12 % surface of internal estuaries

m

il

li

o

n

t

o

n

s

C

y

e

a

r

-1

_%

a

n

tr

o

p

o

g

e

n

ic

e

m

is

s

io

n

(13)

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 51.1 51.2 51.3 51.4 51.5 51.6 51.7 51.8 la ti tu d e ( °N )

Zeebrugge

(14)

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

(15)

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 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

(16)

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

(17)

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

20-28 August 97

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

(18)

pCO

₂

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

(19)

(20)

Annually integrated flux:

+ 4.5 mmol m

-2

_day

-1

_{(exchange coeff. Wanninkhof 1992)}

Surface of the Scheldt plume:

2100 km

2

(21)

Annually integrated flux:

+ 4.5 mmol m

-2

_day

-1

_{(exchange coeff. Wanninkhof 1992)}

Surface of the Scheldt plume:

2100 km

2

Annual emission of CO

₂

:

112 tC day

-1

₌

_26%

Of the inner Scheldt estuary characterised by:

Flux

=

+ 173 mmol m

-2

_day

-1

₌

_{456 tC day}

-1

(22)

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)}

(23)

(24)

pCO

₂

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

O

₂

saturation

-6 -4 -2 0 2 85 95 105 115 125

longitude (°E)

%

(25)

pCO

₂

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

O

₂

saturation

0 1 2 3 4 5 6 7 8 9 10 11 12 90 95 100 105 110

month of the year

(26)

(27)

Annually integrated 



pCO

_{air-sea flux ≈}

_≈

_{≈ 0}

Why?

New primary production = 1.0 mmolC m

-2

_day

-1

(30)

Annually integrated 



pCO

2

≈

≈ 0

Annually integrated CO

₂

_{air-sea flux ≈}

_≈

_{≈ 0}

Why?

New primary production = 1.0 mmolC m

_{Southern Bight of the North Sea}

(31)

Annually integrated 



pCO

2

≈

≈ 0

Annually integrated CO

₂

_{air-sea flux ≈}

_≈

_{≈ 0}

Why?

New primary production = 1.0 mmolC m

_day

-1

(32)

Annually integrated 



pCO

2

≈

≈ 0

Annually integrated CO

₂

_{air-sea flux ≈}

_≈

_{≈ 0}

Why?

New primary production = 1.0 mmolC m

_day

-1

(Migné et al. 1998)

Release of CO

₂

= +13 mmolC m

-2

_day

-1

(33)

Annually integrated 



pCO

2

≈

≈ 0

Annually integrated CO

₂

_{air-sea flux ≈}

_≈

_{≈ 0}

Why?

New primary production = 1.0 mmolC m

_day

-1

(Migné et al. 1998)

Release of CO

₂

= +13 mmolC m

-2

_day

-1

Area 5400 km

2

Whole of Channel

(34)

(35)

pCO

₂

Gulf of Biscay

0 1 2 3 4 5 6 7 8 9 10 11 12 300 320 340 360 380 400 420 440 observed

theoretical as a function of temperature evolution

months of the year

µ

a

tm

Chlorophyll a

0 1 2 3 4 5 6 7 8 9 10 11 12 0.0 0.5 1.0 1.5 2.0

months of the year

µ

g

l

(36)

Air-sea exchange of CO

₂

integrated annually in the Gulf of Biscay:

(37)

Air-sea exchange of CO

₂

integrated annually in the Gulf of Biscay:

Wanninkhof (1992)

- 7.9 mmol m

-2

_day

-1

₌

_{0.17 GtC year}

-1

(38)

Air-sea exchange of CO

₂

integrated annually in the Gulf of Biscay:

Wanninkhof (1992)

- 7.9 mmol m

-2

_day

-1

₌

_{0.17 GtC year}

-1

Extrapolation to the overall European continental shelf (5 million km²)

North Atlantic Ocean (42° to 78°N):

(39)

Air-sea exchange of CO

₂

integrated annually in the Gulf of Biscay:

Wanninkhof (1992)

- 7.9 mmol m

-2

_day

-1

₌

_{0.17 GtC year}

-1

Extrapolation to the overall European continental shelf (5 million km²)

North Atlantic Ocean (42° to 78°N):

Wanninkhof (1992)

=

0.34 GtC year

-1

_{(Sarmiento et al. 1995)}

(40)

Air-sea exchange of CO

₂

integrated annually in the Gulf of Biscay:

Wanninkhof (1992)

- 7.9 mmol m

-2

-2

_day

-1

Tans et al. (1990)

- 7.7 mmol m

-2

_day

-1

Confirms the « continental shelf pump hypothesis » of Tsunogai et al. (1999):

(41)

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

(42)

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

)

(43)

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 )