[CCSM-Ocean] Paper in Biogeosciences

Barbara Ballard bballard at ucar.edu
Wed Apr 8 11:40:37 MDT 2009


The paper below may be of broad interest to folks in the CCSM 
Biogeochemistry,
ocean, and polar working groups.  Thanks. Scott Doney


Steinacher, M., F. Joos, T.L. Frölicher, G.-K. Plattner, and S.C. Doney, 
2009:
Imminent ocean acidification in the Arctic projected with the NCAR global
coupled carbon cycle-climate model, Biogeosciences, 6, 515-533.

The final revised paper in Biogeosciences is available at:
http://www.biogeosciences.net/6/515/2009/bg-6-515-2009.html

Abstract. Ocean acidification from the uptake of anthropogenic carbon is
simulated for the industrial period and IPCC SRES emission scenarios A2 
and B1
with a global coupled carbon cycle-climate model. Earlier studies identified
seawater saturation state with respect to aragonite, a mineral phase of 
calcium
carbonate, as a key variable governing impacts on corals and other 
shell-forming
organisms. Globally in the A2 scenario, water saturated by more than 300%,
considered suitable for coral growth, vanishes by 2070 AD (CO2≈630 
ppm),
and the ocean volume fraction occupied by saturated water decreases from 
42% to
25% over this century. The largest simulated pH changes worldwide occur in
Arctic surface waters, where hydrogen ion concentration increases by up 
to 185%
(ΔpH=−0.45). Projected climate change amplifies the decrease in
Arctic surface mean saturation and pH by more than 20%, mainly due to
freshening and increased carbon uptake in response to sea ice retreat. 
Modeled
saturation compares well with observation-based estimates along an Arctic
transect and simulated changes have been corrected for remaining model-data
differences in this region. Aragonite undersaturation in Arctic surface 
waters
is projected to occur locally within a decade and to become more 
widespread as
atmospheric CO2 continues to grow. The results imply that surface waters 
in the
Arctic Ocean will become corrosive to aragonite, with potentially large
implications for the marine ecosystem, if anthropogenic carbon emissions are
not reduced and atmospheric CO2 not kept below 450 ppm.

-- 
Barbara Ballard
Administrative Assistant III
CCSM Program Office
Oceanography Section
National Center for Atmospheric Research
P.O. Box 3000
Boulder, CO  80307-3000
Phone: (303) 497-1358
Fax:   (303) 497-1700




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