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

根据该合同，PIs将对深海沉积物进行取样，这将为西北非洲气候和植被以及热带大西洋海温和海温梯度的变化提供新的全新世记录。pi将进行为期28天的取心巡航，从沿西北非洲边缘（35oN-10oS）形成带状样带的高积累率地点恢复一系列多核/重力核对。其中四个最有希望的岩心将用于开发非洲气候和植被、亚热带和热带大西洋上升流和海温全新世变化的详细（~40年分辨率）多代理记录。来自热带地区的全新世气候变化的详细记录是罕见的，本提案旨在填补这一观测空白。热带大西洋海温和西北非洲气候与北大西洋海温在年际-多年代际（和千年）时间尺度上的变化具有动态联系。认识到大西洋高纬度和低纬度气候之间的这些联系，PIs建议探索与全新世高纬度冷却事件相关的热带海洋和非洲气候变率的特征。研究小组建议利用新型气相色谱-质谱联用仪（GC/TOF-MS）监测非洲全新世植被变化，建立植被变化的分子生物标志物记录（植物蜡和木质素衍生酚类物质）。非洲气候的变化也将利用陆源（风成）尘埃通量和颗粒大小，以及XRF元素核扫描来重建。本文将利用烯酮、有孔虫Mg/Ca和稳定同位素以及有孔虫普查计数测量，重建热带大西洋海温的全新世变化。沿样带的亚热带至热带热带海温变化对追踪高纬度地区进入热带的百年降温事件具有特别的诊断意义。该项目的结果最终将用于确定这些热带气候、植被和海温信号相互之间的振幅和相位关系，以及相对于北大西洋气候的已知变化。这项研究的一个关键科学成果将是确定百年至千年时间尺度上热带大西洋气候变率的幅度，并了解它们在这些与社会相关的突变气候变化中的作用。

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.