Relationship between glacial CO (sub 2) drawdown and mercury cycling in the western South Atlantic; an isotopic insight

Pronounced changes in the deep Atlantic circulation occurred during glacial stages, which affected the global carbon distribution and the biogeochemical cycles of other elements. Previous studies demonstrated that oceanic mercury is sensitive to the same kind of processes that affect the carbon cycle in glacial-interglacial time scales. We used Hg isotopes to elucidate Hg cycling during the last two glacial-interglacial transitions in the subtropical western South Atlantic. Mass-dependent fractionation (MDF, delta (super 202) Hg) and mass-independent fractionation (MIF, Delta (super 199) Hg) show significant variations and shift toward higher and lower values during the penultimate and Last Glacial Maximum periods, respectively. delta (super 202) Hg variability is in-phase with periods of lower atmospheric CO (super 2) and benthic delta (super 13) C, suggesting that MDF is affected by the same mechanisms that led to atmospheric CO (sub 2) drawdown during glacial stages. In contrast, terrestrial Hg input to our site, boosted by lower sea level and exposure of the continental shelf, dominates the Delta (super 199) Hg variability.