Oceans & Anthropogenic CO2

V.Y. ChowEPS 131

CO2 exchange across sea surfaces in the oceans

Measurement methods of anthropogenic CO2

Distributions & inventories Transport & dominant water masses Impacts

Topics

Dramatic increase of atmospheric [CO2] Keeling Plot (Mauna Loa)

SeasonalityPre-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 CO2 partitioning (mean annual data from 1980s)

Anthropogenic fluxes

Natural fluxes

Mean annual sea surface CO2 exchange

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

uptake emission

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

Measuring Anthropogenic CO2

Distributions & inventories of aCO2

period from ~1800-1994

North Atlantic (15% global oceans) stores 23% global aCO2

Southern hemisphere oceans stores 60%

40% aCO2 stored between 50ºS and 14ºS

Vertically integrated [aCO2]

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

Ocean floor depth

[aCO2] in the oceans

aCO2 transport (ventilation, Revelle factor, H2O masses)

Revelle factor: relates ΔpCO2 w/ ΔDICOceanaCO2 capacity 1/ Revelle factor

formation of mode, intermediate, & deep waters = primary mech. aCO2 transport to ocean interior

aCO2 transport & dominant H2O masses

[aCO2] in Atlantic Ocean

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)

AAIW

[aCO2] in Pacific Ocean

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.

AAIW

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

Major impacts of anthropogenic CO2 uptake

Marine Organisms

Phytoplankton Coralplanktonic mollusk (pteropods) argonite shell

CaCO3 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 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

References

Questions?

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

Potential Density

Table of aCO2