Dissolved inorganic carbon dynamics and CO2 atmospheric exchanges in the inner and outer Scheldt estuary

Dissolved inorganic carbon dynamics

and CO

atmospheric exchanges in the

inner and outer Scheldt estuary

Alberto Vieira Borges

&

Michel Frankignoulle

Université de Liège

Unité d’Océanographie Chimique

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

0 5 10 15 20 25 30 35 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 Mar 93 Jun 93 Mar 94 Nov 94 Jan 95 Aug 95 Nov 95 Jan 96 Mar 96 May 96 July 96 Dec 96 Oct 97 Nov 97 Dec 97 May 98 Oct 98 Feb 99 May 99 Jul 00 Nov 00 salinity p C O2 ( µ a tm )

data binned every 5 of salinity 0 5 10 15 20 25 30 35 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 salinity p C O2 ( µ a tm )

O₂ 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 %

March 1993 0 4 8 12 16 20 24 28 32 0 100 200 300 400 500 NH₄+ NO₃+NO₂ Salinity µ m o l k g -1 NH₄+ _{+ 2O} 2 +H2O  NO3- + 2H3O+

March 1993 0 4 8 12 16 20 24 28 32 0 100 200 300 400 500 NH₄+ NO₃+NO₂ Salinity µ m o l k g -1 NH₄+ _{+ 2O} 2 +H2O  NO3- + 2H3O+ TAlk = 2[CO₃2-_{] + [CO}

March 1993 0 4 8 12 16 20 24 28 32 0 100 200 300 400 500 NH₄+ NO₃+NO₂ Salinity µ m o l k g -1 NH₄+ _{+ 2O} 2 +H2O  NO3- + 2H3O+ TAlk = 2[CO₃2-_{] + [CO}

3-] + [minor] + [OH-] - [H3O+] pH = -log [H₃O+_]

March 1993 0 4 8 12 16 20 24 28 32 2 3 4 5 6 observed TAlk computed Salinity m m o l k g -1

0 5 10 15 20 25 30 35 2 3 4 5 6 Mar 93 Jun 93 Mar 94 Nov 94 Jan 95 Aug 95 Nov 95 Jan 96 Mar 96 May 96 July 96 Dec 96 Oct 97 Nov 97 Dec 97 May 98 Oct 98 Feb 99 May 99 Jul 00 Nov 00 salinity T A lk ( m m o l k g -1 )

data binned every 5 of salinity 0 5 10 15 20 25 30 35 2 3 4 5 6 salinity T A lk ( m m o l k g -1 )

0 5 10 350 450 550 minutes p C O2

CO

air-water fluxes

CO₂ 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

net emission of CO₂ 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 -1 470 tons of C per day

Back of the envelope CO₂ budget for the Scheldt (tC day-1₎

Inputs

CO₂ from the tributaries 50a

Respiration – primary production 270b,c

Acidification from nitrification 250c,d

Outputs

CO₂ emission to the atmosphere 470e

CO₂ transfert to North Sea 35f

Sum

570 505

a _{Abril et al. (2000)} d _{Regnier et al. (1997)}

b _{Soetaert & Herman (1995)} e _{Frankignoulle et al. (1998)}

Atmospheric CO₂ flux:

Atmospheric CO₂ flux:

F = a K dpCO₂

a = CO₂ solubility coefficient = f (S; T)

dpCO₂ = air-water gradient of pCO₂

Atmospheric CO₂ flux:

F = a K dpCO₂ measured

a = CO₂ solubility coefficient = f (S; T) measured

dpCO₂ = air-water gradient of pCO₂ measured

CO₂ exchange coefficient, K, function: Turbulence at air-water interface

Air bubbles Surface films

CO₂ exchange coefficient, K, function:

Turbulence at air-water interface (wind & currents) Air bubbles

CO₂ exchange coefficient, K, function:

Turbulence at air-water interface (wind & currents) Air bubbles

Surface films

K₆₀₀ data binned every 1 m s-1 0 2 4 6 8 10 12 0 10 20 30 40 50 60

Raymond & Cole (2001)

Marino & Howarth (1993) Carini et al. (1996) u₁₀ (m s-1) K6 0 0 ( c m h -1 )

0 2 4 6 8 10 12 14 0 10 20 30 40 50 60 Randers Fjord Scheldt u₁₀ (m s-1) K6 0 0 ( c m h -1 ) Tidal Currents ? Fetch ?

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

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

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

Partial pressure of CO₂ (pCO₂) 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

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

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

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

Surface of the Scheldt plume: 2100 km2

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

Provisional C budget for the Scheldt plume (tC day-1₎

Inputs

CO₂ from the Scheldt 34a

Organic C from the Scheldt 16b _{- 52}c

Organic C from the coast 47c

Outputs

Organic carbon preservation in sediments 62c

CO₂ emission 112a

Sum

97 - 133 175

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

Perspectives

Ste _{Anna Station}

(Antwerp) Belgica

Ste Anna Station (Antwerp)

23 24 25 26 27 28 29 30 3000 4000 5000 6000 7000 8000 0 2 4 6 September 2002 p C O2 ( p p m ) s a lin ity

Belgica (North Sea)

S O N D J F M A M J J A S O N D J F M A M J J near Zeebrugge (salinity 32) S O N D J F M A M J J A S O N D J F M A M J J 150 350 550 750 2000 2001 2002 p C O2 ( p p m )