Collaborative Research: Changing Holocene environments of the Eastern Tropical Atlantic (CHEETA)

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Under this award the PIs will core deep sea sediments that will develop new Holocene records of variations in NW African climate and vegetation and tropical Atlantic SSTs and SST gradients. The PIs will go on a 28-day coring cruise to recover a series of multicore/gravity core pairs from high accumulation rate sites forming a zonal transect along the NW African margin (35oN-10oS). Four of the most promising cores will be used to develop detailed (~40 year resolution) multiproxy records of Holocene variations in African climate and vegetation, and subtropical and tropical Atlantic upwelling and SSTs. Detailed records of Holocene climate variability from the tropics are rare and this proposal aims to fill this observational gap. Tropical Atlantic SSTs and NW African climate are dynamically linked to variations in North Atlantic SSTs at interannual-multidecadal (and millennial) timescales. Recognizing these linkages between high- and low-latitude Atlantic climate, the PIs propose to explore signatures of tropical ocean and African climate variability associated with high-latitude cooling events during the Holocene.The PIs propose to develop molecular biomarker records of vegetation change (plant waxes and lignin-derived phenols) by applying a new design of gas chromatograph-mass spectrometer (GC/TOF-MS) to monitor African vegetation shifts during the Holocene. Changes in African climate will be reconstructed also using terrigenous (eolian) dust fluxes and grain size, and XRF elemental core scanning. Holocene variations in tropical Atlantic SSTs will be reconstructed for this same transect of cores using alkenones, and foraminiferal Mg/Ca and stable isotopes, and foram census count measurements. Subtropical to tropical tropical SST changes along the transect will be particularly diagnostic for tracing the centuryscale high-latitude cooling events into the tropics.Results from this project will ultimately be used to define the amplitude and phasing relations of these tropical climate, vegetation, and SST signals relative to each other, and relative to known changes in North Atlantic climate. A key scientific dividend of this research will be to define the amplitudes of tropical Atlantic climate variability over centennial-millennial timescales, and to understand their role in these abrupt societally-relevant climate shifts.