Reconstructing the Glacial Thermocline at Little Bahama Bank

作为海洋环流的主要特征和全球碳循环的重要组成部分，如果我们要了解第四纪气候波动的过程，就必须考虑温跃层的变化。根据小巴哈马浅滩中下部温跃层中海底有孔虫018和13c的记录，初步结果表明，在约540米瓦特深度的冰川温跃层比今天低了约2oC，富含13c。该项目的目标是确定温跃层内营养物质和物理性质的水深剖面从上一次冰盛期到现在是如何演变的。目标是将北大西洋副热带环流的温跃层演变与物理强迫因素的冰期-间冰期变化、全球碳收支/大气二氧化碳和中间/深水环流联系起来。为了实现这一目标，将在400至1700米的深度范围内收集小巴哈马浅滩沉积良好的南侧的一套岩心。海洋环流的一个主要特征是温跃层的深度，在温跃层中，温暖、混合良好的表层水位于较冷的深水之上。必须知道冰川时期到这一基本界线的深度，才能重建最后一次冰川盛期期间的海洋历史。该项目将利用在小巴哈马浅滩两侧沉积岩芯中发现的底栖有孔虫中的氧和碳同位素来记录气候波动期间温跃层的波动。温跃层厚度、温度和营养物质供应的模式的演变将首次在没有当地海岸效应的开阔海洋环境中确定。

As a primary feature of ocean circulation and key component of the global carbon cycle, changes in the thermocline must be accounted for if we are to understand the processes involved in Quaternary climatic fluctuation. Preliminary results, based on the benthic foraminiferal 018 and 13c records in cores from the mid-and lower-thermocline at Little Bahama Bank, suggest the glacial thermocline at about 540 meters wataer depth was approximately 2oC cooler and more 13c enriched that it is today. The objective for this project is to determine how bathymetric profiles of nutrients and physical properties within the thermocline have evolved from the last glacial maximum to the present. The goal is to relate thermocline evolution in the North Atlantic subtropical gyre to glacial- interglacial changes of physical forcing factors, the global carbon budget/atmospheric pCO2 and intermediate/deep water circulation. In order to accomplish this goal, a suite of cores from the well-sedimented southern flank of Little Bahama Bank will be collected Over the depth range 400 to 1700 meters. %%% A primary feature of ocean circulation is the depth of the thermocline where warm, well-mixed surface water lies on top of colder deep water. the depth to this fundamental boundary must be known for glacial periods in order to reconstruct the history of oceans during the last glacial maximum. This project will use oxygen and carbon iosotopes in benthic foraminifera found in sedimentary cores from the flanks of Little Bahama Bank to document the fluctuations of the thermocline during fluctuations of the climate. The evolution of patterns in theromcline thickness, temperature, and nutrient supply will be determined for the first time in an open ocean environment where local coastal effects will be absent.