Boron Proxies in Paleoceanography and Paleoclimatology – eBook

(Analytical Methods in Earth and Environmental Science) Boron in Paleoceanography and Paleoclimatology (PDF) offers a resource to introduce geoscientists to the prospects and complications of boron proxies, including potential avenues to further refine them.

Anthropogenic carbon dioxide emissions do not only heat our planet but also acidify our oceans. It is presently unclear to which degree Earth’s climate and marine life will be affected by these changes but information from Earth history, especially the geochemical signals of past environmental changes stored in the fossil remains of marine organisms, can assist us to predict possible future changes. This ebook aims to be a primer for scientists who pursue to apply boron proxies in marine carbonates to estimate past seawater carbonate chemistry and atmospheric pCO₂.

Boron proxies (δ¹¹B and B/Ca) were introduced about three decades ago, with subsequent strides being made in understanding their mechanistic functioning. This textbook analyses current knowledge about the aqueous systematics, the inorganic and biological controls on boron isotope fractionation, and incorporation into marine carbonates, in addition to the analytical techniques for measurement of boron proxies. Laboratory and field calibrations of the boron proxies are shortened, and similarities between modern calibrations are explored to propose estimates for proxy sensitivities in marine calcifiers that are now extinct. Example applications show the potential for reconstructing paleo-atmospheric pCO₂ from boron isotopes. Also studied are the sensitivity of paleo-ocean acidity and pCO₂ reconstructions to boron isotope proxy systematics that is presently less well understood, including the seawater alkalinity,  elemental and boron isotopic composition of seawater through time, temperature, and salinity, and their collective impact on the insecurity of paleo-reconstructions.

The B/Ca proxy is based on the same mechanistic principles as the boron isotope proxy, but empirical calibrations suggest seawater pH is not the only controlling factor. B/Ca thus has the potential to provide a second carbonate parameter that could be coupled with δ¹¹B to fully constrain the ocean carbonate system, but the related uncertainties are large. This textbook analyses and examines what is currently known about the B/Ca proxy systematics

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