Biogeosciences
www.biogeosciences.net
1726-4170
1726-4189
6
11
2009
10.5194/bg-6-2661-2009
http://www.biogeosciences.net/6/2661/2009/
http://www.biogeosciences.net/6/2661/2009/bg-6-2661-2009.html
http://www.biogeosciences.net/6/2661/2009/bg-6-2661-2009.pdf
2661
2668
2009-11-25
Rate of Iceland Sea acidification from time series measurements
J. Olafsson
S. R. Olafsdottir
A. Benoit-Cattin
M. Danielsen
T. S. Arnarson
T. Takahashi
Marine Research Institute, Skulagata 4, IS 121 Reykjavik, Iceland
Institute of Earth Sciences, University of Iceland, Sturlugata 7, IS 101 Reykjavik, Iceland
National Energy Authority of Iceland, Grensasvegur 9, 108 Reykjavík, Iceland
Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA
The Iceland Sea is one part of the Nordic Seas. Cold Arctic Water prevails
there and the deep-water is an important source of North Atlantic Deep
Water. We have evaluated time series observations of measured <i>p</i>CO<sub>2</sub> and
total CO<sub>2</sub> concentration from discrete seawater samples during 1985–2008
for the surface and 1994–2008 for deep-water, and following changes in
response to increasing atmospheric carbon dioxide. The surface pH in winter
decreases at a rate of 0.0024 yr<sup>−1</sup>, which is 50% faster than average
yearly rates at two subtropical time series stations, BATS and ESTOC. In the
deep-water regime (>1500 m), the rate of pH decline is a quarter of that
observed in surface waters. The surface seawater carbonate saturation states
(Ω) are about 1.5 for aragonite and 2.5 for calcite, about half of
levels found in subtropical surface waters. During 1985–2008, the degree of
saturation (Ω) decreased at an average rate of 0.0072 yr<sup>−1</sup> for
aragonite and 0.012 yr<sup>−1</sup> for calcite. The aragonite saturation horizon
is currently at 1710 m and shoaling at 4 m yr<sup>−1</sup>. Based on this rate of
shoaling and on the local hypsography, each year another 800 km<sup>2</sup> of
seafloor becomes exposed to waters that have become undersaturated with
respect to aragonite.
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