RUI: Using opal and organic carbon as proxies for wind-driven upwelling during the onset and termination of the African Humid Period in a transect of African margin cores

来自北非的海洋和陆地记录极大地增强了我们对过去地质时期气候变化的原因和影响的理解。具体地说，古生产力变化的代用记录提供了有关上升流强度的信息，从而提供了北非边缘的风力强度。反过来，风力强度的变化已被证明与萨赫勒地区相对干旱的变化有关：过去降水增加的时期是信风减弱和上升流减少的时期，反之亦然。今天，萨赫勒地区的人口极易受到有效降水变化的影响，因此，了解干旱、风力和气候变化之间的联系以及变化的突然程度变得更加重要。这项工作由明尼苏达州麦卡莱斯特学院的一名早期职业教员领导，重点关注与非洲湿润期（AHP，距今11000年至5000年）相关的环境变化，当时北非的环境比现在湿润得多。具体地说，这项工作将评估与AHP的开始和结束相关的上升流变化的时间和突发性，这些变化贯穿非洲西北部边缘20度的纬度跨度。首席研究员将利用沉积物岩心中保存的蛋白石和有机碳的百分比来确定上涌强度的变化，并将这些数据与来自一个单独资助项目的230数据相结合，以计算每种成分的通量。这些努力将提供一个非常丰富和详细的代用数据集，这些代用数据集与整个冰川消融和全新世期间萨赫勒地区的风力、上升流和干旱有关。就更广泛的影响而言，该项目将为中西部一所小型文理学院的一些本科生提供从事海洋科学研究的机会。资金还支持两位早期职业科学家之间的合作。

Marine and terrestrial records from northern Africa have greatly enhanced our understanding of both the causes and effects of climate change in the geologic past. Specifically, proxy records of changes in paleoproductivity yield information about upwelling strength, and therefore wind strength along the North African margin. Changes in wind strength, in turn, have been shown to correlate with changes in the relative aridity of the Sahel: periods of increased precipitation in the past were periods of weaker trade winds and decreased upwelling, and vice verse. Today the population of the Sahel region is highly vulnerable to changes in effective precipitation, making it all the more important to understand the connections between aridity, wind-strength, and climate change, and how abruptly changes can occur.This work, led by an early career faculty member at Macalester College in Minnesota, focuses on the environmental changes associated with the African Humid Period (AHP, 11,000 to 5,000 years before present), a time when northern Africa was characterized by a much wetter environment than it is today. Specifically, the work will assess the timing and abruptness of changes in upwelling associated with the onset and termination of the AHP across a 20-degree span of latitudes along the northwest African margin. The lead researcher will determine changes in upwelling intensity using the percentages of opal and organic carbon preserved in sediment cores, and combine these data with 230Th data from a separately funded project to calculate fluxes of each constituent. These efforts will provide an extraordinarily rich and detailed dataset of proxies related to wind strength, upwelling, and aridity in the Sahel region throughout the deglaciation and the Holocene. In terms of broader impact, this project will offer the opportunity for a number of undergraduates at a small mid-western liberal arts college to engage in ocean sciences research. Funding also supports collaboration between two early career scientists.