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| Titel |
Dissolution of Antarctic shelf carbonates: an insignificant feedback to acidification |
| VerfasserIn |
J. Hauck, K. R. Arrigo, M. Hoppema, G. L. van Dijken, C. Völker, D. A. Wolf-Gladrow |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250059190
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| Zusammenfassung |
| Dissolution of calcium carbonate neutralizes anthropogenic CO2. An upward shift of the
calcite and aragonite saturation horizons exposes carbonate deposits to dissolution which is
an important carbon sink reaction on a time scale of several thousand years for the world
oceans.
In the Southern Ocean, the surface calcite and aragonite saturation states are naturally low
due to cold temperatures. They are further reduced by the uptake of anthropogenic carbon
which is strongest in the top 1000 m. Undersaturation at the surface might occur even before
the underlying water column is completely undersaturated. Therefore, carbonate sediments
on Antarctic shelves are likely to be be among the first to dissolve due to man-made
acidification.
Obviously, we need to know the inventory of CaCO3 in the bioturbated layer of the
Antarctic shelf sediments to quantify the capacity of this negative feedback mechanism. Here,
we present a technique that allows us to spatially interpolate CaCO3 data on the Antarctic
shelves. We derive quantitative relationships between nearly 400 measurements of CaCO3 on
the Antarctic shelves, water depth and satellite-derived primary production in the overlying
water column. This confirms that primary production mainly determines the CaCO3
distribution on the Antarctic shelves: On the one hand, there is hardly any CaCO3 production
when primary production is low. On the other hand, dissolution due to CO2 produced by
remineralization of organic matter dominates in high primary production regions; this
constrains CaCO3 accumulation and preservation to regions with an optimum primary
production level.
These relationships between sedimentary CaCO3, primary production, and water depth
are then applied to produce a map of CaCO3 on all Antarctic shelves. The inventory,
calculated from this interpolated map of CaCO3, amounts to 4 Pg CaCO3, capable to
neutralize about 0.5 Pg C. This, however, is in the same range as estimates of the annual
anthropogenic CO2 uptake in the Southern Ocean. The dissolution of CaCO3 is limited by
slow reaction kinetics, otherwise CaCO3 could disappear from the Antarctic shelves in only
one to a few years. Our analysis suggests that deposits of CaCO3 will dissolve
without releasing a significant buffering signal and that Antarctic acidification will
proceed without being slowed down by dissolution of carbonates from Antarctic
shelves. |
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