Contributions to Science, 3-3 : Paleoclimatology research in Catalonia : special issue / A. Rosell-Melé, guest editor

Reconstructing past seawater pH from boron isotopes in carbonates

Carles Pelejero, Eva Calvo Costa


Since the Industrial Revolution, the CO2 concentration in the atmosphere
has increased substantially, enhancing the greenhouse
effect, which is very much related to current global
warming. Fortunately, the Earth has a series of reservoirs, especially
its oceans, which trap a significant amount of the excess
CO2. This marine absorption of CO2, however, results in
progressive acidification of the oceans, which has detrimental
and possibly devastating effects for marine organisms, particularly
those that construct a skeleton of calcium carbonate
(corals, mussels, clams, etc.). To understand the magnitude of
this problem, it is crucial to know how seawater pH has oscillated
in the past, particularly during those periods of time that
are not covered by instrumental measurements, which are restricted
to the last decade. For this purpose, the isotopic composition
of boron in fossil biogenic carbonates provides a geochemical
indicator, or proxy, which allows reconstruction of the
past variations in seawater pH. In this review, we explain the
theoretical grounds of this proxy, show the empirical calibrations
carried out so far, briefly comment on some aspects of
boron-isotope analysis, and list the results of paleo-pH reconstructions
published so far.

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ISSN: 2013-410X (electronic edition); 1575-6343 (print edition)