Abstract
AbstractMuch uncertainty exists about the state of the oceanic and atmospheric circulation in the tropical Pacific over the last glacial cycle. Studies have been hampered by the fact that sediment cores suitable for study were concentrated in the western and eastern parts of the tropical Pacific, with little information from the central tropical Pacific. Here we present information from a suite of sediment cores collected from the Line Islands Ridge in the central tropical Pacific, which show sedimentation rates and stratigraphies suitable for paleoceanographic investigations. Based on the radiocarbon and oxygen isotope measurements on the planktonic foraminifera Globigerinoides ruber, we construct preliminary age models for selected cores and show that the gradient in the oxygen isotope ratio of G. ruber between the equator and 8°N is enhanced during glacial stages relative to interglacial stages. This stronger gradient could reflect enhanced equatorial cooling (perhaps reflecting a stronger Walker circulation) or an enhanced salinity gradient (perhaps reflecting increased rainfall in the central tropical Pacific).
Highlights
It has been demonstrated that the tropical Pacific ocean-atmosphere system exerts a critical control on global climate on timescales from interannual (El Niño–Southern Oscillation) to decadal and longer
The multisensor track (MST) density data and down-core G. ruber δ18O for all sediment cores are shown in Figure S1 in the supporting information and archived at the World Data Center for Paleoclimatology at the National Climate Data Center
Marine Isotope Stage (MIS) boundaries are assigned based on correlation of the oxygen isotope data to the global benthic stack of Lisiecki and Raymo [2005], or in the absence of oxygen isotope data, by correlating the MST density data to cores with oxygen isotope data
Summary
It has been demonstrated that the tropical Pacific ocean-atmosphere system exerts a critical control on global climate on timescales from interannual (El Niño–Southern Oscillation) to decadal and longer. DiNezio et al [2011] analyze the Paleoclimate Model Intercomparison Project’s Last Glacial Maximum (LGM) simulations and assess the degree to which they follow these expectations. While they find an overall increase in the strength of the atmospheric circulation in the tropics for all models, the LGM tropical Pacific atmospheric circulation in each model is different and reflects a complex interplay between various factors. These factors include the tendency of decreased water vapor in the cooler atmosphere to increase circulation and the tendency of the Northern Hemisphere ice sheets to shift atmospheric circulation patterns to the south, as well as the emergence of an Indonesian Maritime Continent that shifts convection to the Indian Ocean
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