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 CO 2 Flux, ° x 5° estimates of monthly sea to air CO 2 flux - 940,000  pCO 2 observations, after Takahashi et al., years of NCEP/NCAR monthly average winds plotted by Jim Christian, CCCMA/IOS

Anthropogenic CO 2 in the Ocean Total 118  19 PgC Sabine et al. (2004) Science 305:  ~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 modelling

AR7W potential temperature (0–50 m) and SST

AR7W total inorganic carbon Central Labrador Sea (100–500 m) OSD/BIO

Labrador 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 ppm ppm ppm --- C 4 MIP Results: Friedlingstein et al. SRES: A2  A Positive Feedback to Climate Change

Simulated Land + Ocean CO 2 Uptake (PgC/yr) Land Ocean Land Uptake is Highly Uncertain

Canadian Model of Ocean Carbon (CMOC-1) Includes: Ocean Biological Pump + Calcifiers + N 2 fixers: [Zahariev, Denman and Christian]Developed (i) in 1-D MLM: (i) in 1-D MLM: Denman and Peña, 1999, 2002 (ii) in regional 3-D OGCM: Haigh, Denman & Hsieh, 2001

Canadian Model of Ocean Carbon (CMOC-1) Air-Sea CO 2 Fluxes (mols-C m -2 yr -1 ) Zahariev,Christian,Denman CCCma/IOS Annual mean ΔpCO 2 (referenced to 1995) [Takahashi et al, 2002]

(a)(b) (d) (c) 20 µm Four 'PFTs': Plankton Functional Types The PARADIGM Group, Oceanography, March 2006

CO 2 in the Ocean & the 'Biotic' Pumps DIC = CO 2 + HCO 3 _ + CO 3 = >90% Atmosphere Ca HCO 3 _  CaCO 3 + H 2 O + CO 2 'POC' + 'DOC' Photosynthesis: 'Organic Pump' nCO 2 + 2nH 2 O  nCH 2 O + nO 2 + nH 2 O 'Carbonate Pump' Removes C and –ve charge - so increases pCO 2 '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, 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 (CaCO 3 ) Pump - Coccolithophorid Emiliania huxleyi Image courtesy of Southampton Oceanography Centre, UK SEM image SeaWiFS image 25 April 1998 SeaWiFS image 16 July 2000

Impact of CO 2 uptake on the ocean Ocean CO2-uptake has lowered the average ocean pH (increased acidity) by approximately 0.1 since Consequences for marine ecosystems may include reduced calcification by shell- forming organisms, and in the longer-term, the dissolution of carbonate sediments.

Adding CO 2 Increases Ocean Acidity K 1 K 2 CO 2 + H 2 O  HCO H +  CO H + This decrease in pHalso increases surface ocean pCO 2, which opposes invasion of atmospheric CO 2 into the ocean: This decrease in pH also increases surface ocean pCO 2, which opposes invasion of atmospheric CO 2 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]

Phytoplankton Grown Under Different CO 2 Concentrations ~300 ppm ~780 – 850 ppm Riebesell et al Nature, 407,

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 Science, 305: Corals Coccolithophorids

Weight % of CaCO 3 in Sediments From: Archer, D.E., Global Biogeochemical Cycles, 10(1),

Saturation Layer in N. Pacific is shrinking Feely et al Science, 305: 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