Developing a High-Resolution Sea-Level Record to Measure the Magnitude and Timing of the Catastrophic 8.2 ka Freshwater Release - Implications for North Atlantic Climate Dynamics

开发高分辨率海平面记录来测量8.2 ka灾难性淡水释放的规模和时间——对北大西洋气候动力学的影响约8200年前发生的一次百年尺度的突然降温，被称为“8.2 ka事件”，据信是由一个巨大的冰坝湖（阿加西湖）的淡水灾难性地释放到北大西洋造成的。然而，对这一显著气候变化的全面理解受到了关于融水脉冲的幅度、性质和时间的不确定性的阻碍。目前对与8.2 ka事件相关的淡水容量的估计相当于海平面上升了~0.3至~1.4米。在密西西比三角洲地区，基底泥炭（源自半咸水）侵蚀了更新世固结基底，墨西哥湾的微潮状态使海平面变化的重建具有极高的分辨率。在这个项目中，PI将使用14C测定基底泥炭样品的年代，以跟踪这一关键时间间隔内的海平面变化。采样分辨率约为10厘米。稳定的碳同位素数据将提供数据来估计泥炭形成生态系统的盐度，从而建立与海平面的关系。这些综合数据将用于估计海平面上升的总量以及确定这一事件的时间。这些数据还将允许PI提供由劳伦泰德冰盖直接输送的淡水量的估计，并提供输入数据，以探索淡水释放的不同机制和地点的气候影响，使用耦合的海洋-大气模型。这些结果将为海洋环流对各种淡水强迫情景的敏感性提供新的见解，这将有助于更好地理解北大西洋在温室世界中持续变新鲜的后果。该项目将为一名博士生和四名本科生实地助理提供培训。

Developing a High-Resolution Sea-Level Record to Measure the Magnitude and Timing of the Catastrophic 8.2 ka Freshwater Release - Implications for North Atlantic Climate DynamicsAn abrupt, century-scale cooling ~8200 years ago, known as the "8.2 ka event," is believed to have been caused by the catastrophic release of freshwater from a giant ice-dammed lake (Lake Agassiz) into the North Atlantic Ocean. However, a comprehensive understanding of this prominent climate change is hampered by uncertainty about the magnitude, nature, and timing of this meltwater pulse. Current estimates of the freshwater volume associated with the 8.2 ka event correspond to an equivalent sea-level rise of ~0.3 to ~1.4 m. In the Mississippi Delta region, basal peat (brackish water derived) encroaches on a consolidated Pleistocene basement and the microtidal regime in the Gulf of Mexico enables the reconstruction of sea-level change with exceptionally high resolution. In this project, the PI's will 14C date basal-peat samples that track sea-level change during this critical time interval. Sampling resolution will be on the order of 10 cm. Stable carbon isotope data will provide data to estimate the salinity of the peat-forming ecosystem so as to establish the relationship with sea level. The combined data will be used to estimate the total amount of sea-level rise as well as determining the timing of this event. These data will also permit the PI's to provide an estimate of the amount of freshwater delivered directly by the Laurentide Ice Sheet, as well as providing input data to explore the climatic effects of different mechanisms and locations of freshwater release using a coupled ocean-atmosphere model. These results will provide new insights about the sensitivity of ocean circulation to various scenarios of freshwater forcing, which could help to better understand the consequences of continued freshening of the North Atlantic Ocean in the greenhouse world. The project will provide training for one PhD student, as well as four undergraduate field assistants.