Collaborative Research: Deglaciation Chronology of the Des Moines Lobe - implications for ice sheet dynamics and climate change

在最后一次冰消期，劳伦泰德冰盖的得梅因叶占据了一个贯穿大陆中部的主要地形凹陷，并将冰盖的核心排干。要研究的问题是，得梅因叶的衰退与一系列不受时间限制的再进有关。在一次衰退中，巨石冰碛形成，随后形成了冰川湖阿加西斯的南部边缘。通过对冰碛上洼地中的湖泊取芯，可以使用放射性碳测年来确定冰碛的年龄，以估计冰川消退率，并提供阿加西湖开始的年龄。这项研究的直接目标是确定大石碛的年龄。阿加西湖是覆盖北美最大的前冰川湖，在末次冰期结束时，它与各种突然的气候变化有关，但该湖的开始年龄未知。这一合作建议建立在过去和目前的研究在两个方面：首先，资金是有保障的研究冰川消退模式的地区年轻比大石碛沿着断面进入加拿大。这一支持将建立Laurentide冰盖主要部分的冰川消退年表。第二，阿加西湖另外两个拟议出口的研究已接近完成（安大略的雷霆湾和阿尔伯塔的麦克默里堡）。在每个地区，冰消年代表定义了这些潜在的溢流道何时可能活跃。该方案将确定剩余排水口开始排水的时间，并允许整个系统的时间整合。这项工作的更广泛的影响是理解冰盖动力学和气候变化历史的地球系统的一个主要地貌元素的分支。

During the last deglaciation, the Des Moines lobe of the Laurentide Ice Sheet occupied a major topographic depression through the mid-continent and drained the core of the ice sheet. The problem to be studied is that recession of the Des Moines lobe has been implicated in a series of readvances not constrained in time. During one recession, the Big Stone Moraine formed and subsequently formed the southern edge of glacial Lake Agassiz. By coring lakes in depressions on the moraine, the age of the moraine can be determined using radiocarbon dating to provide estimates on deglaciation rates, as well as providing an age for the beginning of Lake Agassiz. The immediate goal of this research is to establish the age of the Big Stone Moraine. Lake Agassiz was the largest pro-glacial lake to cover North America, and it has been implicated in a variety of abrupt climate changes during its history at the end of the last glaciation, yet the beginning age of the lake is unknown. This collaborative proposal builds on past and current research in two ways: First, funding is secured to study deglaciation patterns in areas younger than the Big Stone Moraine along transects into Canada. This support will establish the deglaciation chronology of a major portion of the Laurentide Ice Sheet. Second, research at two other proposed outlets of Lake Agassiz is nearly complete (Thunder Bay, Ontario and Fort McMurray, Alberta). In each area the deglacial chronology defines when these potential spillways could have been active. This proposal will establish when drainage began in the remaining outlet, and allow temporal integration of the entire system. The broader impacts of this work are the ramifications for the understanding ice sheet dynamics and climate change history for a major geomorphic element of the earth system.