Geoscience Reference
In-Depth Information
5
Arctic Ocean
NE. Pacific
3
4
2
3
W. Eq. Pacific
1
7
2
1900
2000
2100
6
NE. Atlantic
(380-980 m)
1
3
5
2100
1900
2000
5
2
4
E. Eq. Pacific
1
3
4
1900
2000
2100
2
3
1
2
Southern Ocean
3
1900
2000
2100
1
2
1900
2000
2100
1
1900
2000
2100
atmospheric
p
CO
2
(matm)
surface-ocean pH
(SWS)
surface saturation
1000
8.2
7
6
5
4
3
2
1
0
calcite
800
600
400
200
0
1900
8.1
8.0
7.9
7.8
7.7
aragonite
under-saturation
1950
2000
Year
2050
2100
1900
1950
2000
Year
2050
2100
1900
1950
2000
Year
2050
2100
Figure 15.1
Projected regional changes in ocean chemistry likely to be experienced by particularly vulnerable ecosystems and compared with global-scale
surface-ocean changes (Turley et al. 2010). The transient simulation of climate and carbonate chemistry was performed with the UVic Earth System Climate
Model using observed historical boundary conditions to 2006 and the SRES A2 scenario to 2100 (Eby et al. 2009). For each of the six illustrative high-risk
marine ecosystems [Arctic Ocean, Southern Ocean, north-east Pacii c margin, intermediate-depth north-east Atlantic (500-1500 m), western equatorial Pacii c,
eastern equatorial Pacii c] we have identii ed in this paper, the blue-shaded band indicates the annual range in ocean saturation state with respect to aragonite,
while the green shaded band indicates the range for calcite saturation. Area-average surface-ocean conditions are calculated for all regions with the exception
of the north-east Atlantic where area-average benthic conditions between 380 and 980 m have been used. The thickness of the line indicates the seasonal
range, with the threshold of undersaturated environmental conditions marked as a horizontal dashed line. The varying evolution in the magnitude of the
seasonal range between different regions is due to the complex interplay between changes in stratii cation, ocean circulation, and sea-ice extent, and distorted
due to the non-linear nature of the saturation scale. The corresponding regions from which the annual ranges are calculated are shown shaded. Global ocean
surface averages (bottom) are shown, from left to right: CO
2
partial pressure (p CO
2
), pH
SWS
, and calcite and aragonite saturation. Figure reproduced from Turley
et al . ( 2010 ) with permission from Elsevier.
Although it is critical to provide one or a few
acidity level(s) that should not be exceeded, it is a
very challenging task which requires a large body
of scientii c evidence, including at the ecosystem
level and on food webs, and the knowledge of the
level of risk that society is prepared to accept.
15.3
Ecosystems at risk
Three areas of the global ocean are more suscepti-
ble to ocean acidii cation than others, either
because ocean acidii cation will be more severe
(polar regions and the deep sea) or because it acts
