Oceans & Anthropogenic CO 2 V.Y. Chow EPS 131

 CO 2 exchange across sea surfaces in the oceans  Measurement methods of anthropogenic CO 2  Distributions & inventories  Transport & dominant water masses  Impacts Topics

Dramatic increase of atmospheric [CO 2 ] Keeling Plot (Mauna Loa) Seasonality Pre-1974 Scripps data

 Main sources: fossil fuel burning & land use change  50% stays in atmosphere, rest in 2 primary sinks: 20% terrestrial biosphere, 30% ocean Atmospheric CO 2 partitioning (mean annual data from 1980s) Anthropogenic fluxes Natural fluxes

Mean annual sea surface CO 2 exchange  North Atlantic: Gulf Stream & NA Drift transport warm H 2 O north, cools & releases heat. Cool water = CO 2 sink  Equatorial Pacific (0.8-1 Pg): divergent surfaces, cold upwelling = outgassing uptakeemission

 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: aCO 2 = Anthropogenic CO 2 for this presentation Measuring Anthropogenic CO 2

Distributions & inventories of aCO 2 period from ~  North Atlantic (15% global oceans) stores 23% global aCO 2  Southern hemisphere oceans stores 60%  40% aCO 2 stored between 50ºS and 14ºS Vertically integrated [aCO 2 ]

 aCO 2 ocean invasion via air-sea exchange  highest [aCO 2 ] 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 Ocean floor depth [aCO 2 ] in the oceans

 aCO 2 transport  (ventilation, Revelle factor, H 2 O masses) Revelle factor: relates ΔpCO 2 w/ ΔDIC Ocean aCO 2 capacity 1/  Revelle factor  formation of mode, intermediate, & deep waters = primary mech. aCO 2 transport to ocean interior aCO 2 transport & dominant H 2 O masses

[aCO 2 ] in Atlantic Ocean  high wind speed (  gas transfer) & low [aCO 2 ] initial = AAIW & SAMW large uptake  transported equatorward & downward  transport + water masses’ large volumetric contribution to S. Hemisphere thermocline = high aCO 2 (>20Pg C) AAIW

[aCO 2 ] in Pacific Ocean  NPIW 3.2Pg C  Atlantic: AAIW = aCO 2 penetration limit  Pacific: large amount aCO 2 deeper than NPIW  many IW’s in N. Pacific, cannot attribute signal to single IW. AAIW

 total uptake (1800 – 1994) = 118  19 Pg C  w/o ocean uptake atmospheric CO 2 +55ppm  future estimate atmospheric CO 2 levels > 800ppm  CO 2 acid gas  surface ocean pH  = ocean acidification   continue trend = biggest pH drop in 5million years Major impacts of anthropogenic CO 2 uptake

Marine Organisms Phytoplankton Coral planktonic mollusk (pteropods) argonite shell  CaCO 3 dissolves in the upper ocean  calcification rates  25-45% if 800ppm  alter marine food webs + Δ(T,S,nutrients)

 Freely, R.A. et al. Impact of Anthropogenic CO 2 on the CaCO 3 System in the Oceans. Science. Vol. 305:  Sabine, C.L. et al. The Oceanic Sink for Anthropogenic CO2. Science. Vol. 305:  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.   bin/php/sciencehistory.show.php?section_id=11&article_id=143    References

Questions?

Distribution of anthropogenic CO2 on the (A) 26.0 and (B) 27.3 potential density surfaces. Potential Density

Table of aCO 2