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| Titel |
Acidification of the Mediterranean Sea during the 21st century |
| VerfasserIn |
Briac Le Vu, Julien Palmiéri, James C. Orr, Jean-Claude Dutay, Florence Sevault |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250092216
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| Publikation (Nr.) |
 EGU/EGU2014-6545.pdf |
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| Zusammenfassung |
| We modeled the carbon cycle in the Mediterranean Sea to study how its changes due to
climate change and rising levels of atmospheric CO2 may differ from those typical of the
global ocean. More specifically, we coupled offline an ocean biogeochemical model
(PISCES) to a regional eddy-permitting model of the Mediterranean Sea (NEMO-MED8,
1/8° nominal horizonal resolution) using forcing from coupled regional climate model
simulations of which the ocean circulation component was identical. Here we describe the
simulated changes in pH and the associated carbonate system during the 21st century.
Separate simulations were made with climate forcing for a hindcast (1965-2008) and for the
future (2000-2100). For the former, climate and CO2 forcings were based on observations;
for the latter, both climate and CO2 were driven by the IPCC SRES-A2 scenario. Our
hindcast simulation over the period 1965-2008 allowed us to evaluate the model
and assess recent variability of the carbonate system. In our future simulation, we
used separate tracers to distinguish (1) the change due to climate change and the
increase in atmospheric CO2 (from 370 to 800 ppm) and (2) the change due only to
climate change (holding atmospheric CO2 to the year-2000 level of 370 ppm). By
difference, we isolated the geochemical effect (anthropogenic CO2 perturbation). The
hindcast simulation demonstrates that the model captures the amplitude and phase of
the annual cycle of temperature, pCO2 and pH, in agreement with data from the
DYFAMED station. That seasonal variability of surface pCO2 is everywhere driven
by variations in temperature. These results lends support that the model is able to
quantify the acidification of the Mediterranean Sea during the industrial period and
for the future. However, they do not constrain the model’s simulated effects of
future climate change on ocean circulation and ocean biology, both of which in turn
influence the carbon cycle. Similar to estimates for the global ocean, the future
simulation predicts a reduction in surface pH (acidification) of the Mediterranean Sea
between 2000 and 2050 of 0.1 units (total scale); however, that change is not identical
everywhere. It is 0.02 units less where there is strong mixing with deep waters
(Gulf of Lyon, Rhodes Gyre and south Adriatic Sea), which are impoverished in
anthropogenic CO2. It is also less, but only by 0.005 units, in regions most affected by
incoming water from the Atlantic Ocean (near the Strait of Gibralter). Conversely,
acidification is more intense (the magnitude of the pH change is larger) by 0.03 units
in coastal areas such as the Dardanelles Strait, and near outflow from the Rhone
and Po rivers, whose waters are more acidic and less able to buffer the increase in
CO2. The simulated changes in surface pH in the Mediterranean Sea are almost
entirely driven only by the direct geochemical effect from rising atmospheric CO2. |
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