Biogeochemical Proxies in Scleractinian Corals used to Reconstruct Ocean Circulation.

摘要

We utilize monthly 14C data derived from coral archives in conjunction with ocean circulation models to address two questions: 1) how does the shallow circulation of the tropical Pacific vary on seasonal to decadal time scales and 2) which dynamic processes determine the mean vertical structure of the equatorial Pacific thermocline. Our results directly impact the understanding of global climate events such as the El Nino-Southern Oscillation (ENSO). To study changes in ocean circulation and water mass distribution involved in the genesis and evolution of ENSO and decadal climate variability, it is necessary to have records of climate variables several decades in length. Continuous instrumental records are limited because technology for continuous monitoring of ocean currents has only recently been available, and ships of opportunity archives such as C O S contain large spatial and temporal biases. In addition, temperature and salinity in surface waters are not conservative and thus can not be independently relied upon to trace water masses, reducing the utility of historical observations. Radiocarbon (I4C) in sea water is a quasi-conservative water mass tracer and is incorporated into coral skeletal material, thus coral 14C records can be used to reconstruct changes in shallow circulation that would be difficult to characterize using instrumental data. High resolution A14C timeseries such as these, provide a powerful constraint on the rate of surface ocean mixing and hold great promise to augment onetime surveys such as GEOSECS and WOCE. These data not only provide fundamental information about the shallow circulation of the Pacific, but can be used as a benchmark for the next generation of high resolution ocean models used in prognosticating climate change.