Variability of Climate and Carbon Sycling in the Tropical Pacific During Periods of Abrupt Thermocline Shift

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Abstract: Under this award the PI will try to understand changes in thermocline circulation and ultimately net CO2 fluxes in the tropical Pacific during the period AD 1800 to the present. High-precision radiocarbon (DELTA14C + - 2 per mil) measurements are proposed of annual and seasonal coral bands from Palmyra Atoll in the mid-tropical Pacific (6N, 162W) and Galapagos Islands in the eastern tropical Pacific (0, 91W) using AMS (accelerator mass spectrometry) techniques. This study will provide an historical record of ENSO and Pacific Decadal Oscillation. It will enable correlation with the new 14C record from Galapagos coral in the eastern tropical Pacific that reveals a prominent decrease of 14C during the early 1800s which indicates a rapid change in the source of waters upwelled in the eastern tropical Pacific. It is important to know whether the sudden shift in surface 14C values in the eastern ropical Pacific during the early 1800s was a local event or if it was wide-spread, i.e., extended into the mid-Pacific. Potential impact on the net annual flux of CO2 from this extensive supersaturated region of the surface ocean to the atmosphere will be determined by modeling of the carbon cycle in collaboration with other investigators. This study addresses fundamental gaps in our knowledge of past climate change and its influence on the cycling of CO2 between atmosphere and ocean. These results will aid in our understanding of how natural variability in climate can influence the ability of the ocean to absorb excess CO2 produced from fossil fuel and biomass burning. This grant supports a graduate student and an undergraduate student and provides hands-on experience that will prepare them for careers as scientists and educators. The PI is involved with developing outreach activities in conjunction with middle and high school youths.