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Oceans & Anthropogenic CO 2. V.Y. Chow EPS 131. Topics. CO 2 exchange across sea surfaces in the oceans Measurement methods of anthropogenic CO 2 Distributions & inventories Transport & dominant water masses Impacts.
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Oceans & Anthropogenic CO2 V.Y. ChowEPS 131
Topics • CO2 exchangeacross sea surfaces in the oceans • Measurement methods of anthropogenic CO2 • Distributions & inventories • Transport & dominant water masses • Impacts
Dramatic increase of atmospheric [CO2] Keeling Plot (Mauna Loa) Seasonality Pre-1974 Scripps data
AtmosphericCO2 partitioning (mean annual data from 1980s) Natural fluxes Anthropogenic fluxes • Main sources: fossil fuel burning & land use change • 50% stays in atmosphere, rest in 2 primary sinks: 20% terrestrial biosphere, 30% ocean
Mean annual sea surface CO2 exchange uptake emission • North Atlantic: Gulf Stream & NA Drift transport warm H2O north, cools & releases heat. Cool water = CO2 sink • Equatorial Pacific (0.8-1 Pg): divergent surfaces, cold upwelling = outgassing
Measuring Anthropogenic CO2 • ΔC* : estimation of pre-industrial preformed DIC levels for recently ventilated water masses (using transient tracer data) • MIX approach: analyze the hydrographic and inorganic carbon data using a multi-parameter mixing analysis. Note: aCO2 = Anthropogenic CO2 for this presentation
Distributions & inventories of aCO2period from ~1800-1994 Vertically integrated [aCO2] • North Atlantic (15% global oceans) stores 23% global aCO2 • Southern hemisphere oceans stores 60% • 40% aCO2 stored between 50ºS and 14ºS
[aCO2] in the oceans Ocean floor depth • aCO2 ocean invasion via air-sea exchange highest [aCO2] in near-surface waters • majority confined to thermocline. • depth determined by transport speed of near-surface accumulation into ocean interior. • isopycnal surfaces = main transport surfaces
aCO2 transport & dominant H2O masses • aCO2 transport (ventilation, Revelle factor, H2O masses) • Revelle factor: relates ΔpCO2 w/ ΔDIC OceanaCO2 capacity 1/ Revelle factor • formation of mode, intermediate, & deep waters = primary mech. aCO2 transport to ocean interior
[aCO2] in Atlantic Ocean AAIW • high wind speed (gas transfer) & low [aCO2]initial = AAIW & SAMW large uptake • transported equatorward & downward • transport + water masses’ large volumetric contribution to S. Hemisphere thermocline = high aCO2 (>20Pg C)
[aCO2] in Pacific Ocean AAIW • NPIW 3.2Pg C • Atlantic: AAIW = aCO2 penetration limit • Pacific: large amount aCO2 deeper than NPIW • many IW’s in N. Pacific, cannot attribute signal to single IW.
Major impacts of anthropogenic CO2 uptake • total uptake (1800 – 1994) = 118 19 Pg C • w/o ocean uptake atmospheric CO2 +55ppm • future estimate atmospheric CO2 levels > 800ppm • CO2 acid gas surface ocean pH = ocean acidification • continue trend = biggest pH drop in 5million years
Marine Organisms • CaCO3 dissolves in the upper ocean • calcification rates 25-45% if 800ppm • alter marine food webs + Δ(T,S,nutrients) planktonic mollusk (pteropods) argonite shell Phytoplankton Coral
References • Freely, R.A. et al. Impact of Anthropogenic CO2 on the CaCO3 System in the Oceans. Science. Vol. 305:362-366. • Sabine, C.L. et al. The Oceanic Sink for Anthropogenic CO2. Science. Vol. 305:367-371. • Wallace, D.W.R. Introduction to special section: Ocean measurements and models of carbon sources and sinks. Global Biogeochemical Cycles. Vol. 15:1, pp3-10. • http://www.aip.org/pt/vol-55/iss-8/p30.html#ref • http://www.igbp.kva.se/cgi- bin/php/sciencehistory.show.php?section_id=11&article_id=143 • http://www.peopleandplanet.net/doc.php?id=2373 • http://www.spacedaily.com/news/climate-04zz.html • http://www.bbsr.edu/pubs/cdi04/cdi04acid/cdi04acid.html
Potential Density Distribution of anthropogenic CO2 on the (A) 26.0 and (B) 27.3 potential density surfaces.
