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Earth and Space Sciences · 术语表

什么是 Mg/Ca ratio (proxy)？

Definition 24.6 University Earth and Space Sciences — Year 2 · 第 24 章 — Climate Archives and Proxies

The Mg/Ca ratio (proxy) is the ratio of magnesium to calcium in the calcite of foraminiferal shells, in $\mathrm{mmol}/\mathrm{mol}$ , used as a measure of the temperature of the water in which the shell grew through an exponential calibration

\text{Mg/Ca} = B\,\mathrm{e}^{A T},

with $A$ close to $0.09\,/{}^{\circ}\mathrm{C}$ for planktonic species and $B$ specific to the species.

Two calibrations. (a) The benthic calibration of : the calcite is heavier than the water (on their own scales) by 0.21 per mil more for each degree of cooling. (b) The Mg/Ca of a planktonic species, as predicted from temperature alone and as fitted to 235 shells. — Two calibrations. (a) The benthic calibration of Proposition 24.2: the calcite is heavier than the water (on their own scales) by $0.21$ per mil more for each degree of cooling. (b) The Mg/Ca of a planktonic species, as predicted from temperature alone and as fitted to 235 shells.

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