Seawater strontium and Sr/Ca variability in the Atlantic and Pacific oceans

摘要

Seawater Sr and Sr/Ca exhibit spatial gradients of 2-3% globally, with the deep ocean more enriched relative to the surface. In latitudinal transects, the highest surface values are found at high latitudes and associated with areas of upwelling. A pronounced upper ocean vertical Sr gradient is attributable to the production of celestite skeletons by surface-dwelling acantharia, coupled to a shallow dissolution cycle. The upper ocean residence time of Sr with respect to celestite cycling is much shorter than its global oceanic residence time. Although the magnitude of seawater Sr/Ca variability is relatively small, it is significant with respect to high-precision paleoceanographic applications. Sr/Ca gradients in the contemporary ocean also complicates evaluating Quaternary changes in seawater Sr/Ca that may have resulted from other processes, such as aragonite recrystallization during sea-level low stands.