Doctoral Dissertation Research: The Geographic Extent of Late Pleistocene Subsurface Ocean Warming in the Northern Atlantic Ocean Basin and the Origin of Heinrich Events

本博士论文研究项目将研究海因里希事件的触发机制，海因里希事件是全球气候突变的一种广泛认可的表达。海因里希事件被解释为从劳伦泰德冰盖崩解的冰山大量喷发，在上一个冰河时期，劳伦泰德冰盖覆盖了北美大陆的大部分地区。海因里希事件的气候背景是全球性的。因此，确定这些事件是千年尺度全球气候变化的一个组成部分。然而，引发这些事件的物理过程仍然知之甚少。该博士论文研究项目将利用海底生物的镁钙比，开发北大西洋地下水温的高分辨率记录，以覆盖已知的海因里希事件，以评估海洋环流变化引起的海因里希事件的外部触发机制。该方法将为海底生物的镁钙古测温提供一种新的分析方法。对从拉布拉多海外海盆升起的一个海洋沉积物岩心的分析表明，在该岩心位置的海因里希事件的地层特征出现之前，底部水温就已经变暖了。为了确定这种模式作为海因里希事件的强迫机制的作用，有必要复制和进一步评估这种模式的地理分布。来自雷克雅内斯海岭和拉布拉多海的勘探数据表明，该项目在感兴趣的深度和位置的海洋沉积物岩心包含海因里希事件特征和实现该项目研究目标所需的材料。冰盖突变不稳定和海洋变化的研究对未来气候具有重要意义。确认中深度海洋变暖在触发过去冰盖不稳定方面发挥了重要作用，将为类似配置的南极冰盖部门的潜在未来行为提供关键见解。该项目可以为目前正在开发的用于预测陆冰损失和随之而来的海平面上升的冰盖模型提供验证。该项目还将产生新的数据，以测试博士生开发的用于等离子体质谱仪的新配件的准确性，以便更有效地测量海洋沉积物中的Mg-Ca古温度值。该项目应增进对冰盖对海洋环流和温度当前和将来可能发生的变化的反应的了解，这些因素是海平面上升预估中引起关注和不确定的最大原因之一。作为博士论文研究进步奖，该项目将提供支持，使有前途的学生建立一个独立的研究生涯。

This doctoral dissertation research project will examine the triggering mechanisms of Heinrich events, which are a widely recognized expression of abrupt global climate change. Heinrich events are interpreted as massive discharges of icebergs calved from the Laurentide Ice Sheet, the ice mass that covered a large share of the North American continent during the last ice age. The climatic context of Heinrich events was global in scale. Identifying these events therefore is an integral part of millennial-scale global climate change. The physical processes that triggered these events remain poorly understood, however. This doctoral dissertation research project will develop high-resolution records of North Atlantic Ocean subsurface water temperature bracketing known Heinrich events using magnesium-to-calcium ratios in seafloor-dwelling organisms in order to evaluate an external triggering mechanism for Heinrich events attributed to changes in oceanic circulation. This approach will employ a new analytical method for Mg-Ca paleothermometry on seafloor-dwelling organisms. Analysis of one ocean sediment core raised from the outer Labrador Sea basin suggested that bottom-water temperatures warmed before stratigraphic signatures of Heinrich events at that core location. Replication and further assessment of the geographic distribution of this pattern is necessary in order to establish its role as a forcing mechanism of Heinrich events. Exploratory data from the Reykjanes Ridge and the Labrador Sea have shown that the ocean sediment cores targeted for this project at the depths and locations of interest contain Heinrich event signatures and material necessary in order to carry out this project's research goals.The study of abrupt ice sheet destabilization and oceanic change has significant implications for future climate. Confirmation that intermediate-depth ocean warming played a significant role in triggering past ice-sheet instabilities will provide critical insights into potential future behavior of similarly configured Antarctic ice-sheet sectors. The project could provide validation for ice-sheet models currently being developed for projections of land-ice loss and attendant sea level rise. The project also will yield new data to test the accuracy of a new accessory developed by the doctoral student for use with plasma mass spectrometers in order to more effectively measure Mg-Ca paleothermometry in marine sediments. The project should improve understanding of the response of ice sheets to current and possible future changes in ocean circulation and temperature, factors which are among the greatest causes for concern and uncertainty in projections of sea-level rise. As a Doctoral Dissertation Research Improvement award, this project will provide support to enable a promising student to establish an independent research career.