Past changes in ocean carbonate chemistry - Ocean Acidification - page 37

10 7

B

10 6

10 5

0.2

0.0

-0.2

-0.4

10 4

E

-0.6

-0.8

10 3

-1.0

D

-1.2

A

10 2

C

10 1

100 200 500 1000 2000 5000 10000

Atmospheric CO 2 (ppmv)

Figure 2.6 Estimated maximum change in surface-ocean pH (labelled contour lines) as a function of i nal atmospheric CO 2 pressure, and the transition
time over which this CO 2 pressure is linearly approached from 280 ppmv (modii ed after Caldeira and Wickett 2003). A, Glacial-interglacial CO 2 changes; B,
slow changes over the past 300 Myr; C, historical changes in ocean surface waters; D, unabated fossil-fuel burning over the next few centuries. E, The range
of the timescale of carbon input and p CO 2 estimates during the Palaeocene-Eocene Thermal Maximum (PETM) (which was probably approached from a CO 2
level signii cantly higher than 280 ppmv). Note that surface-ocean pH changes were probably much smaller during the PETM than suggested in the i gure
because of lower sensitivity to carbon perturbations and substantially higher initial p CO 2 (e.g. Zeebe et al. 2009 ; Stuecker and Zeebe 2010 ).

2.7 Acknowledgements
We thank Jelle Bijma, Ken Caldeira, Jean-Pierre
Gattuso, Lina Hansson, and Andy Knoll for com-
ments on an earlier version of the manuscript. This
work was supported by NSF grants OCE09-02869
and OCE09-27089 to REZ. It is a contribution to the
'European Project on Ocean Acidii cation' (EPOCA)
which received funding from the European
Community's Seventh Framework Programme
(FP7/2007-2013) under grant agreement no. 211384.

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