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以测量灾难性的8.2ka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冷却，被称为“8.2ka事件”，被认为是由一个巨大的冰堰湖(阿加西湖)向北大西洋灾难性的淡水释放造成的。然而，对这种显著的气候变化的全面理解受到了对这种融水脉冲的规模、性质和时间的不确定性的阻碍。目前对与8.2ka事件相关的淡水量的估计相当于海平面上升了约0.3至~1.4米。在密西西比三角洲地区，基底泥炭(来自微咸水)侵蚀了一个统一的更新世基底，而墨西哥湾的小潮制度使以极高的分辨率重建海平面变化成为可能。在这个项目中，PI将跟踪这一关键时间间隔内的海平面变化的基础泥炭样品的14C日期。采样分辨率将在10厘米量级。稳定的碳同位素数据将为估计泥炭形成生态系统的盐度提供数据，从而建立与海平面的关系。合并后的数据将被用来估计海平面上升的总量，以及确定这一事件的时间。这些数据还将使PI能够估计Laurentide冰盖直接输送的淡水量，并提供输入数据，以利用海洋-大气耦合模式探索不同淡水释放机制和地点的气候影响。这些结果将提供关于海洋环流对各种淡水强迫情景的敏感性的新见解，这可能有助于更好地理解北大西洋在温室世界中持续淡水的后果。该项目将为一名博士生和四名本科生现场助理提供培训。

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.