Present day CO2 cycle in the coastal ocean and possible evolution under global change

(1)

Present day CO

₂

cycle in the coastal ocean

and

possible evolution under global change

Alberto V. Borges

Chemical Oceanography Unit

Université de Liège

Belgium

www.co2.ulg.ac.be

Shanghai, 18 September 2007 http://www.co2.ulg.ac.be/

(2)

Present day CO

₂

cycle in the coastal ocean

(3)

Shanghai, 18 September 2007

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

Issue

(4)

Marginal seas (Fluxes in mol C m

-2

_yr

-1

₎

High latitude:

Barents Sea

Bristol Bay

Pryzd Bay

Ross Sea

-3.6

-0.2

-2.2

-1.8

Temperate latitudes:

Baltic Sea

North Sea

English Channel

Gulf of Biscay

US Middle Atlantic Bight

East China Sea

-0.8

-1.4

0.0 -2.9

-1.2

-2.1

Sub-tropical & tropical latitudes:

US South Atlantic Bight

South China Sea

Southwest Brazilian coast

+2.5

+1.8

+1.3

mangrove marsh estuary coral reef marginal sea upwelling

Borges (2005) Estuaries 28(1), 3-27

(5)

Marginal seas

Borges (2005) Estuaries 28(1), 3-27

Latitudinal variability in surface area also counts !

Continental shelf surface area

0° - 30°

30° - 60°

60° - 90°

0

25

50

75 Northern Hemisphere

Southern Hemisphere

14 %

50 %

8 %

13 %

1 %

Latitude

(6)

Estuaries

Estuarine Plume (Outer estuary)

Limit of salt intrusion

Geographic limit of the coast

(estuarine mouth)

Tidal Marsh

Limit of tidal influence

river

Inner estuary

tidal river

Salinity Gradient

Saltmarsh

Tidal Flats

Abril & Borges (2004)

Where does the coastal ocean start ?

Arthur Chen

Alberto Borges

C,N & P inputs

by Kempe,

Meybeck,

(7)

CO

₂

emission from 16

inner estuaries

<5

5 to 30 30 to 60 60 to 80

0

1

2

3

4

5

6

7 mol C m

-2

yr

-1

num

be

r of

ob

s

e

rv

a

ti

o

n

s

Estuaries

(Fluxes in mol C m

-2

_yr

-1

₎

Temperate estuaries (12)

46 mol C m

-2

_yr

-1

Tropical estuaries (4)

19 mol C m

-2

_yr

-1

High latitude estuaries ?

(8)

Estuaries

Borges et al. (2006) ECSS 70(3), 375-387

0

100

200

300

400

0

100

200

300

400 Gazeau et al. (2004)

Gazeau et al. (2004)

Gattuso et al. (1998)

Caffrey (2004)

Heterotrophic

Autotrophic

GPP (mol C m

-2

y

-1

)

R (

m

o

l C m

-2

y

-1

)

Net Ecosystem Production NEP = GPP – R

<NEP> = - 32.4 molC m

-2

_yr

-1

_{(n=65) = strongly heterotrophic}

Riverine CO

₂

input = 10% of total CO

₂

emission

0 10 20 30 40 50 60 70 80

0

100

200

300

400 Rh

Ra

Lo

El

Sad

Em

YR

Th Gi Sat

Sch

El = Elbe

Em = Ems

Gi = Gironde

Lo = Loire

Ra = Randers

Rh = Rhine

Sad = Sado

Sat = Satilla

Sch = Scheldt

Th = Thames

YR =York River

freshwater residence time (d)

% C

O

2 em

issi

on due

to

ve

n

til

at

io

n

of

ri

ve

rine C

O

2

(9)

Coastal -0.05 Pg C y

-1

_{Open -1.57 Pg C y}

-1

_{Global -1.61 Pg C y}

-1

Coastal +0.18 Pg C y

-1

Open +0.71 Pg C y

-1

Global +0.90 Pg C y

-1

↑

27%

Coastal -0.13 Pg C y

-1

Open -2.06 Pg C y

-1

Global -2.19 Pg C y

-1

↑

6%

Coastal -0.10 Pg C y

-1

Open -0.22 Pg C y

-1

Global -0.33 Pg C y

-1

↑

50%

↑ 3%

Up-scaling

(10)

↑ 3%

Up-scaling : ecosystem diversity counts !

Overall coastal ocean small CO

₂

sink (

–0.05 PgC yr

-1

₎

Near-shore systems (estuaries, mangroves, marshes, coral reefs,

upwelling systems) strong sources (+0.40 PgC yr

-1

₎

Marginal seas strong sink (

–0.45 PgC yr

-1

₎

(11)

↑ 3%

PgC yr

-1

_{% total}

Estuaries

0.324

81.1 Marsh waters

0.036

9.0 Mangroves waters

0.033

8.2 Coral reefs

0.005

1.3 Upwelling

0.002

0.5 Nearshore systems

0.400

100 These are also the most vulnerable ecosystems to

human pressure !

Strong feedbacks on increasing atmospheric CO

₂

?

Up-scaling : ecosystem diversity counts !

(12)

Possible evolution under global change

(13)

Mixing,

stratification

Circulation

Light

Nutrients

Climate

Temperature

Nutrient utilization

efficiency

Atmospheric

deposition

Ocean biota

Atmospheric CO

₂

Carbon sinks & sources

Seawater

CO

₂

Carbonate

chemistry

Rain ratio

(CaCO

₃

/POC)

Stoichiometry

(Si/C/N/P/Fe)

Ocean biota

C-partitioning

(POC-DOC-TEP)

N, P, Si inputs

Eutrophication

Nutrient & C inputs regulation

Changes of hydrological cycle

C inputs

Modified from Riebesell (2007) SOVOC meeting

(14)

Mixing,

stratification

Circulation

Light

Nutrients

Climate

Temperature

Nutrient utilization

efficiency

Atmospheric

deposition

Ocean biota

Atmospheric CO

₂

Carbon sinks & sources

Seawater

CO

₂

Carbonate

chemistry

Rain ratio

(CaCO

₃

/POC)

Stoichiometry

(Si/C/N/P/Fe)

Ocean biota

C-partitioning

(POC-DOC-TEP)

N, P, Si inputs

Eutrophication

Nutrient & C inputs regulation

Changes of hydrological cycle

C inputs

(15)

Borges et al. (2007) in prep.

Changes in stratification : Tasman shelf

J

F M A M

J

A

S O

N D

8

10

12

14

16

18

20 SST

(

°C)

J

F M A M

J

A

S O

N D

250

300

350

400

450 SST anomaly < -0.5°C

SST anomaly > 0.5°C

-0.5°C < SST anomaly < 0.5°C

pC

O

2 @14°

C

(

µ

at

m

)

144.5 145.0 145.5 146.0 146.5 147.0 147.5 148.0 148.5 149.0 149.5 150.0 150.5 Longitude (°E) 46.5 46.0 45.5 45.0 44.5 44.0 43.5 43.0 42.5 42.0 41.5 41.0 40.5 La ti tu de ( °S) Hobart

Tasmania

40 transects obtained during

22 cruises from 1991 to 2003

(16)

-3

-2

-1

0

1

2

3 -60

-40

-20

0

20

40

60 r

2 = 0.61

r

2 = 0.77

( )

Spring-Summer

Fall-Winter

SST anomaly (°C)

pC

O

2 @

14°

C

a

nom

al

y

(µ

at

m

)

Monthly anomalies : X

’ = X

_obs

- <X>

_monthly

Borges et al. (2007) in prep.

(17)

-3

-2

-1

0

1

2

3 -60

-40

-20

0

20

40

60 Fall Winter

Spring Summer

enhanced DIC

input by

vertical mixing

enhanced

primary

production

lower DIC

input by

vertical mixing

lower

primary

production

SST anomaly (°C)

pC

O

2 @

14 °C

an

o

m

al

y (

µ

at

m

)

Increasing stratification

Increasing mixing

Borges et al. (2007) in prep.

(18)

1982-2005 mean of daily u

₁₀

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5 -2.0

-1.0

0.0

1.0

2.0 SST anomaly (°C)

F

anom

al

y (

m

o

l m

-2

d

-1

)

↑ of 2°C in SST for 2100 at these latitudes from Hirst (1999) using IPCC

“business-as-usual” IS92a radiative forcing scenario

⇒

CO

₂

sink -6.4 → -8.7 mmolC m

-2

_d

-1

_{(~36% increase in CO}

2 sink, strong

negative feedback)

Changes in stratification : Tasman shelf

increase of SST

(19)

Mixing,

stratification

Circulation

Light

Nutrients

Climate

Temperature

Nutrient utilization

efficiency

Atmospheric

deposition

Ocean biota

Atmospheric CO

₂

Carbon sinks & sources

Seawater

CO

₂

Carbonate

chemistry

Rain ratio

(CaCO

₃

/POC)

Stoichiometry

(Si/C/N/P/Fe)

Ocean biota

C-partitioning

(POC-DOC-TEP)

N, P, Si inputs

Eutrophication

Nutrient & C inputs regulation

Changes of hydrological cycle

C inputs

(20)

Plattner et al. (2005) SCOR conference "The ocean in a high CO

₂

world"

50% reduction of wind stress

⇒

↓ 50% in NPP

⇒

↓ 75% in grazing

⇒

↓ 50% in export pdt

⇒

↓ 50% in CO

₂

source

Mainly related to the ↓ vertical

input of DIC and ↓ of k

California upwelling system

(21)

But climate change → increase in coastal upwelling

→ increase in CO

₂

emission (?)

→ positive feedback on increasing atmospheric CO

₂

(?)

(22)

Mixing,

stratification

Circulation

Light

Nutrients

Climate

Temperature

Nutrient utilization

efficiency

Atmospheric

deposition

Ocean biota

Atmospheric CO

₂

Carbon sinks & sources

Seawater

CO

₂

Carbonate

chemistry

Rain ratio

(CaCO

₃

/POC)

Stoichiometry

(Si/C/N/P/Fe)

Ocean biota

C-partitioning

(POC-DOC-TEP)

N, P, Si inputs

Eutrophication

Nutrient & C inputs regulation

Changes of hydrological cycle

C inputs

(23)

Observed & Expected (IPCC 4)

changes in sea ice

Difference (%) from 1979-1990

mean

Satellite observations (1979-2005)

Mean change for all IPCC models

Change in Bergen Climate Model

Spread of the most likely scenarios

Spread of all IPCC models

Olsen et al. (2007) SOVOC meeting

(24)

Bates et al. (2006) GRL 33, L23609, doi:10.1029/2006GL027028

Arctic Ocean sink for CO

₂

has tripled over the last 3

decades (24 Tg yr

-1

_{to 66}

Tg yr

-1

_{) due to sea-ice}

retreat

Future sea-ice melting

enhancing air-to-sea CO

₂

flux by 28% per decade

(25)

Temperature change → Ecological regime shifts in the Arctic ?

e.g. occurrence of coccolithophorid blooms in the Bering Sea

from 1997 onwards

Temperature change on the Arctic Ocean

Broerse et al. (2003) Cont. Shelf Res., 23:1579

–1596.

(26)

Temperature change on the Arctic Ocean

9400 PgC organic C buried in the 100 m of tundra and taiga

Permafrost thawing

Coastal Erosion

Increased precipitation

can mobilise organic carbon

increase CO

₂

source of near-shore zones

(27)

Mixing,

stratification

Circulation

Light

Nutrients

Climate

Temperature

Nutrient utilization

efficiency

Atmospheric

deposition

Ocean biota

Atmospheric CO

₂

Carbon sinks & sources

Seawater

CO

₂

Carbonate

chemistry

Rain ratio

(CaCO

₃

/POC)

Stoichiometry

(Si/C/N/P/Fe)

Ocean biota

C-partitioning

(POC-DOC-TEP)

N, P, Si inputs

Eutrophication

Nutrient & C inputs regulation

Changes of hydrological cycle

C inputs

(28)

Ocean acidification : buffer factor

Sarmiento et al. (1998) Nature 393:245-249

Penetration of CO

₂

into the oceans

⇒ decrease of the buffer capacity of seawater

⇒ reduces the uptake of anthropogenic CO

₂

(29)

Ocean acidification : buffer factor

Thomas et al. (2007) GBC, doi:10.1029/2006GB002825

(30)

Mixing,

stratification

Circulation

Light

Nutrients

Climate

Temperature

Nutrient utilization

efficiency

Atmospheric

deposition

Ocean biota

Atmospheric CO

₂

Carbon sinks & sources

Seawater

CO

₂

Carbonate

chemistry

Rain ratio

(CaCO

₃

/POC)

Stoichiometry

(Si/C/N/P/Fe)

Ocean biota

C-partitioning

(POC-DOC-TEP)

N, P, Si inputs

Eutrophication

Nutrient & C inputs regulation

Changes of hydrological cycle

C inputs

(31)

Ocean acidification : calcification

Calcification :

Ca

2+

_{+ 2HCO}

3 -

→ CaCO

3 + H

2 O +

CO

2 Ca

2+

_{+ CO}

3 2-

→ CaCO

3 Rost & Riebesell (2004) in Coccolithophores. From Molecular Processes to Global Impact

Increase in CO

₂

→ decrease of calcification

→ negative feedback

(32)

Based on Suzuki & Kawahata (2003) and Bates (2002)

pCO

₂

coral reef – pCO

₂

ocean (ppm)

Christmas Island

-80

Shiraho reef

7 Fanning atoll

30 Canton atoll

15 Palau reef

46 Majuro atoll

23 South Male atoll

6 Northern Great Barrier Reef

29 Southern Great Barrier Reef

12 Hog reef (1994)

26 Hog reef (1995)

16 Hog reef (1996)

16 Average

12

(33)

LEG 2

Coccolithophorid bloom in the Gulf of Biscay (June 2006)

LEG 1

Suykens & Borges (unpubl.) PEACE project

(34)

Coccolithophorid bloom in the Gulf of Biscay (June 2006)

35.40

35.50

35.60

35.70 2310

2320

2330

2340

2350

2360

salinity

T

A

(

µ

m

o

l k

g

-1

)

-30

-20

-10

0

240

260

280

300

320

340 r

2 =0.84

TA anomaly (µmol kg

-1

)

pC

O

2 @13°

C

(

p

m

)

conservative

mixing

calcification

( )

Ocean acidification : calcification

(35)

(IS92c)

(IS92a)

(IS92e)

Ocean acidification : calcification

↓ 22 % of coral reef calcification for 2100 (“business-as-usual” IS92a IPCC)

(Gattuso et al. 1999)

Present day coral reef calcification 0.072 PgC yr

-1

_{(Gattuso et al. 1998)}

⇒ feedback of 0.009 PgC yr

-1

_{(with Ψ = 0.6 from Frankignoulle et al. 1994)}

Small compared to the overall sink of -0.45 PgC yr

-1

_{of marginal seas}

(36)

Ocean acidification : calcification

Global pelagic calcification 0.6 – 1.6 PgC yr

-1

_{(Balch et al. 2007)}

Coastal pelagic calcification 0.1

– 0.3 PgC yr

-1

_{(based on Balch et al. 2005)}

Doubling of atmospheric CO

₂

for 2100 (“business-as-usual” IS92a IPCC scenario)

⇒ decrease of coastal pelagic calcification of 0.006

– 0.016 PgC yr

-1

_{(based on}

Gehlen et al. 2007)

⇒ feedback of 0.004

– 0.010 PgC yr

-1

_{(with Ψ = 0.6 from Frankignoulle et al. 1994)}

Small compared to the overall sink of -0.45 PgC yr

-1

_{of marginal seas}

(37)

Ocean acidification : effects on biota

(38)

Mixing,

stratification

Circulation

Light

Nutrients

Climate

Temperature

Nutrient utilization

efficiency

Atmospheric

deposition

Ocean biota

Atmospheric CO

₂

Carbon sinks & sources

Seawater

CO

₂

Carbonate

chemistry

Rain ratio

(CaCO

₃

/POC)

Stoichiometry

(Si/C/N/P/Fe)

Ocean biota

C-partitioning

(POC-DOC-TEP)

N, P, Si inputs

Eutrophication

Nutrient & C inputs regulation

Changes of hydrological cycle

C inputs

(39)

Nutrient and C inputs

(40)

Nutrient and C inputs

Gregg et al. (2005) GRL, 32, L03606,

doi:10.1029/2004GL021808

Behrenfeld et al. (2006) Nature

doi:10.1038/nature05317

(41)

Nutrient and C inputs

Belgian coastal zone (North Sea)

0

500 1000

1500

2000

19

30

19

35

19

40

19

45

19

50

19

55

19

60

19

65

19

70

19

75

19

80

19

85

19

90

19

95

20

00

20

05 Phaeocystis

Summer

diatom

Spring

diatom

mgC m

-3

Maximum phytoplankton biomass

1950

1960

1970

1980

1990

2000

Pristine

Lancelot et al. (2007) JMS 64:216-228

(42)

Nutrient and C inputs

Nutrient inputs (kT yr

-1

)

1950

0 1960

1970

1980

1990

2000

10

20

30

40 DIN

DIP

0

2

4

6 DI

N

DI

_P

Air-sea CO

₂

flux (mmol C m

-2

yr

-1

)

1950

1960

1970

1980

1990

2000

-0.8

-0.4

0.0

0.4

0.8 source of CO

₂

sink of CO

₂

Organic carbon inputs (T yr

-1

)

1950

0 1960

1970

1980

1990

2000

5

10

15

20 NEP (mmol C m

-2

yr

-1

)

1950

1960

1970

1980

1990

2000

-1.6

-0.8

0.0

0.8

1.6 heterotrophic

autotrophic

Gypens & Lancelot (in prep.)

(43)

Mixing,

stratification

Circulation

Light

Nutrients

Climate

Temperature

Nutrient utilization

efficiency

Atmospheric

deposition

Ocean biota

Atmospheric CO

₂

Carbon sinks & sources

Seawater

CO

₂

Carbonate

chemistry

Rain ratio

(CaCO

₃

/POC)

Stoichiometry

(Si/C/N/P/Fe)

Ocean biota

C-partitioning

(POC-DOC-TEP)

N, P, Si inputs

Eutrophication

Nutrient & C inputs regulation

Changes of hydrological cycle

C inputs

(44)

Summary ?

1 box model :

- Increase of CO

₂

sink in the

coastal ocean mainly due to net

ecosystem metabolism (NEM) due

to increase of nutrient delivery.

- Decrease of calcification and

increase of diagenetic CaCO

₃

dissolution have a minor role.

Andersson & Mackenzie (2004) Front Ecol Environ 2: 348

–353

Mackenzie et al. (2004) Biogeosciences 1:11

–32

(45)

1. More CO

₂

observatories (moorings, repeat tracks, repeat stations,

…)

2. Adapted typologies for scaling CO

₂

fluxes.

3. Several on-going 3D models (California current, North Sea, EU scale, North

America scale

…), but can we go global ?

(i.e. enough knowledge ? computing power ?)

Ways forward ?

(46)

For organizing this event :

Nancy Rabalais, Jack Middelburg & Sylvie Roy

For slides and/or ideas :

Nathalie C. Gypens & Christiane Lancelot

Kasper Plattner & Niki Gruber

Are Olsen

Ulf Riebesell