Indentification of Non-Steady State Changes in Surface OceanCirculation from Radiocarbon in Corals

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-Major objectives are to establish the relative amounts of fossil fuel CO2 in three regions of the surface Pacific, and to understand the nature of circulation changes that have occurred at these sites over the past two centuries. The three regions to be studied are the Norm Pacific (Hawaiian Islands, 20ÝN, 156ÝW), western equatorial Pacific (Nauru Island, 1ÝS, 167ÝE), and the eastern equatorial Pacific (Galapagos Islands, 1ÝS, 91ÝW). The methods used in this study are the measure of high grecision A'4C using AMS (accelerator mass spectrometry) techniques and stable isotopes (if O and sl3C) of annually banded coral skeletons. To link these results with circulation changes that may have taken place several thousands of years ago, another major objective is to compare interannual variability in surface mLxing and circulation in the North Atlantic during the past century (Druffel, 1997, in press) to that which existed earlier in the Holocene. High precision &'4C in ancient reef corals from South Florida will allow us to determine whether large pulses of ventilation took place at the end of the Hypsithermal (4200 yBP), during a very large shin in atmospheric &'4C (2700 yBP) and just before the Medieval Was Period (1300 yBP). These studies will add knowledge about the nature of variability in the ocean, surface or deep, on human time scales. 14C data provides critical tests for ocean circulation models and theories of the role of the ocean in past climate change. Modeling exercises will be performed by the PI to uncover non steady state changes in near surface circulation in the tropical and subtropical areas of the Pacific and Atlantic Oceans.