The Carbon Cycle within the Oceans

Allyn Clarke

With much help from

Ken Denman, Glen Harrison and others

Global Carbon Reservoirs and Fluxes

(Sarmiento and Gruber, 2006, Sabine et al, 2004)

Pre-Industrial

Global Carbon Reservoirs and Fluxes

(Sarmiento and Gruber, 2006, Sabine et al, 2004)

Is the ocean uptake changing?

• Improved estimates of ocean uptake of CO2 suggest little change in the ocean carbon sink of 2.2 ± 0.5 GtC yr–1 between the 1990s and the first five years of the 21st century.

• Models indicate that the fraction of fossil fuel and cement emissions of CO2 taken up by the ocean will decline if atmospheric CO2 continues to increase.

Solubility Pump

Annual Total Air-Sea CO2 Flux, 1995- 4° x 5° estimates of monthly sea to air CO- 4° x 5° estimates of monthly sea to air CO22 flux flux- 940,000 - 940,000 pCOpCO22 observations, after Takahashi et al., observations, after Takahashi et al., 20022002- 41 years of NCEP/NCAR monthly average winds- 41 years of NCEP/NCAR monthly average winds

plotted by Jim Christian, CCCMA/IOSplotted by Jim Christian, CCCMA/IOS

Anthropogenic CO2 in the Ocean

TotalTotal118 118 19 PgC 19 PgC

Sabine et al. (2004) Science 305: 367-371.Sabine et al. (2004) Science 305: 367-371.

~48% of all fossil fuel emissions have ended up in the ocean, ~ 1/3 of its potential storage

Biogeochemical studies in the Labrador Sea - observations and modellingBiogeochemical studies in the Labrador Sea - observations and modelling

AR7W potential temperature (0–50 m) and SST

AR7W total inorganic carbonCentral Labrador Sea (100–500 m)

OSD/BIO

Pic

op

hyt

op

lan

kto

n (

log

cel

ls m

-2)

8

9

10

11

12

13

Sm

all n

ano

ph

yto

pla

nkt

on

(lo

g c

ells

m-2

)

8

9

10

11

12

13

Year

94 95 96 97 98 99 00 01 02 03 04 05 06

Lar

ge

nan

op

hyt

op

lan

kto

n (

log

cel

ls m

-2)

8

9

10

11

12

13

Labrador Shelf and Slope PhytoplanktonLabrador Shelf and Slope Phytoplankton

Small cells are increasing

Medium cells are not changing

Large cells are decreasing

Coupled Climate-Carbon Cycle Models Sequester Less Carbon

Coupled - Uncoupled

--- 200 ppm ---

--- 1000ppm ---

1850

1850

2100

2100

--- 300ppm ---

CC44MIP Results:MIP Results:Friedlingstein et alFriedlingstein et al..

SRES: A2SRES: A2

A Positive A Positive Feedback to Feedback to Climate ChangeClimate Change

Simulated Land + Ocean CO2 Uptake (PgC/yr)

-6 0

1212

0

Land Ocean

1850 18502100 2100

Land Uptake is Highly UncertainLand Uptake is Highly Uncertain

fup

fnm

N

D

fdn

fzn

fzd2

Z

fzm

XP120

fnp

P

fpz

fzd1

fpd fpm

120 m

50 m XP50 fdm

Canadian Model of Ocean Carbon (CMOC-1)Includes: Ocean Biological Pump + Calcifiers + N2 fixers:

[Zahariev, Denman and Christian]

Developed Developed (i) in 1-D MLM:(i) in 1-D MLM: Denman and Peña, 1999, 2002

(ii) in regional 3-D OGCM:(ii) in regional 3-D OGCM: Haigh, Denman & Hsieh, 2001

Canadian Model of Ocean Carbon (CMOC-1)

Air-Sea COAir-Sea CO22 Fluxes (mols-C m Fluxes (mols-C m-2-2 yr yr-1-1))

Zahariev,Christian,Denman CCCma/IOS

Annual mean ΔpCO2 (referenced to 1995) [Takahashi et al, 2002]

(a) (b)

(d)(c)

20 µm

Four 'PFTs': Plankton Functional Types

The PARADIGM Group, Oceanography, March 2006The PARADIGM Group, Oceanography, March 2006

CO2 in the Ocean & the 'Biotic' Pumps

DIC = CO2 + HCO3

_ + CO3

=

>90%>90%

AtmosphereAtmosphere

Ca2+ + 2HCO3

_ CaCO3 + H2O + CO2

'POC' + 'DOC''POC' + 'DOC'

Photosynthesis: Photosynthesis:

'Organic Pump''Organic Pump'

nCO2 + 2nH2O nCH2O + nO2 + nH2O

'Carbonate Pump''Carbonate Pump'

Removes C and –ve charge

- so increases pCO2

'Calcite' 'Calcite'

Iron Fertilization Studies

•Joint Canada / Japan – University / Government experiment at OWS Papa – July 2002 under Canadian SOLAS program

•Major findings published in Deep-Sea Research, Part II, Volume 53, issues 20-22, 2006

•22 scientific papers

•Result was similar to that of the other iron fertilization experiments. See a response in the productivity but very little observable increase in carbon sequestration.

Carbonate (CaCO3) Pump - Coccolithophorid Emiliania huxleyi

Image courtesy of Southampton Image courtesy of Southampton Oceanography Centre, UKOceanography Centre, UK

SEM imageSEM image

SeaWiFS image SeaWiFS image 25 April 199825 April 1998

SeaWiFS image SeaWiFS image 16 July 200016 July 2000

Impact of CO2 uptake on the ocean

• Ocean CO2-uptake has lowered the average ocean pH (increased acidity) by approximately 0.1 since 1750.

• Consequences for marine ecosystems may include reduced calcification by shell-forming organisms, and in the longer-term, the dissolution of carbonate sediments.

Adding CO2 Increases Ocean Acidity

K1 K2CO2 + H2O HCO3

- + H+ CO32- + 2H+

This decrease in pHThis decrease in pH also increases surface also increases surface ocean pCOocean pCO22, which opposes invasion of , which opposes invasion of

atmospheric COatmospheric CO22 into the ocean: into the ocean:

a positive feedback

Surface pH is Decreasing

?

[prepared by Arne Körtzinger (IFM,Kiel) for the IMBER Science Plan on the basis of WOCE data: Schlitzer, 2000]

http://ioc.unesco.org/iocweb/co2panel/Publications.htm

Phytoplankton Grown Under Different CO2 Concentrations

~300 ppm~300 ppm

~780 –~780 –850 ppm850 ppm

Riebesell et al. 2000. Nature, 407, 364-367.Riebesell et al. 2000. Nature, 407, 364-367.

Summary

• The oceans are a significant sink for carbon• Canadian observations and ocean modellers

have contributed greatly to our ability to model the ocean carbon cycle.

• Models project a diminishing relative contribution of the ocean sink

• Iron fertilization is unlikely to be a useful mitigation technique

• Ocean acidification has potential for serious impacts on marine ecosystems

Thank You

Oceanic Acidity is Not Uniform: Saturation Depth Patterns

Feely et al. 2004. Science, 305: 362-366.

CoralsCorals

CoccolithophorCoccolithophoridsids

Weight % of CaCO3 in Sediments

From: Archer, D.E., 1996. Global Biogeochemical Cycles, 10(1), 159-174.

Saturation Layer in N. Pacific is shrinking

Feely et al. 2004. Science, 305: 362-366.

S N

Present

Pre-industrial

Impacts from wetlands and hydro reservoirs

• Observed increases in atmospheric methane concentration, compared with preindustrial estimates, are directly linked to human activity, including agriculture, energy production, waste management, and biomass burning.

• Constraints from methylchloroform observations show that there have been no significant trends in OH radical concentrations, and hence in methane removal rates, over the past few decades (see Chapter 2).

• The recent slow down in the growth rate of atmospheric methane since about 1993 is thus likely attributed to the atmosphere approaching an equilibrium during a period of near constant total emissions.

• However, future methane emissions from wetlands are likely to increase in a warmer and wetter climate, and to decrease in a warmer and drier climate.

AR7W silicate and nitrate(60–200 m)

ERD/BIO

AR7W chlorophyll and bacteria (0–100 m) & total organic carbon (water column)

ERD/BIO

AR7W zooplankton

biomass(0–100 m)

ERD/BIO