The seminal proposition by Arrhenius (1952) that colder periods favor higher productivity oceans than warmer ones, together with the relatively recent hypothesis linking the surface ocean export productivity levels and atmospheric pCO2 have motivated a renewed interest in the reconstruction of the ocean’s paleoproductivity from deep-sea sediments. In this paper we present a record of the relative magnitude and timing of the paleoexport of organic matter to the sea-floor for the last 250 Kyr for the western equatorial Pacific region. The benthic foraminifera preserved in deep-sea sediments are used to estimate the organic matter flux to the sea floor and indirectly they are also a measure of the organic carbon export of from the photic layer. This paleoexport record shows a remarkable coherence with the ice record, as indicated by the δ18O of benthic foraminifera. We further estimate the relative importance of changing nutrients and upper ocean mixing rates to explain the observed paleoproductivity fluctuations. The record of changes in nutrient concentrations is based on the interpretation of the Δδ18OPB between planktics and benthics as a paleonutrient tracer. To estimate the magnitude of the physical forcing, or the upper ocean mixing rates, we use a simple box model, together with a paleotemperature record based on the interpretation of the Δδ18OGsPo between two planktic foraminifera living at different depths within the mixed layer. Paleoexport, the nutrient content, and the ocean mixing rates records are compared to estimate the relative importance of each mechanism in explaining the observed fluctuations of the paleoexport record.
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- Nutrient, Mixing and Export Indices: A 250 Kyr Paleoproductivity Record from the Western Equatorial Pacific
J. C. Herguera
- Springer Berlin Heidelberg