Collaborative Research: Deglaciation Chronology of the Des Moines Lobe - implications for Ice Sheet Dynamics and Climate Change

在最后一次冰川消融期间，劳伦蒂德冰盖的得梅因冰盖占据了穿过中大陆的一个主要地形凹陷，并排干了冰盖的核心。需要研究的问题是，得梅因肝叶的衰退与一系列不受时间限制的再推进有关。在一次经济衰退期间，大石头冰川形成了，随后形成了冰川湖阿加西的南缘。通过对冰雹凹陷中的湖泊进行取芯，可以使用放射性碳测年来确定冰雹的年龄，以提供对冰川消退率的估计，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头冰川的年龄。阿加西斯湖是覆盖北美的最大的前冰川湖泊，在上一次冰川末期的历史上，它与各种突然的气候变化有关，但该湖的开始年龄尚不清楚。这项合作提案以两种方式建立在过去和当前研究的基础上：第一，获得资金，研究加拿大境内横断面上比大石头冰川更年轻的地区的冰川消融模式。这一支持将建立劳伦蒂德冰盖主要部分的冰川消融年代学。其次，阿加西湖另外两个拟议的出口(安大略省的桑德湾和艾伯塔省的麦克默里堡)的研究接近完成。在每个地区，消冰期年表定义了这些潜在的溢洪道可能在什么时候活跃。这项提议将确定剩余排水口何时开始排水，并允许整个系统的时间整合。这项工作的更广泛影响是对理解冰盖动力学和气候变化历史的影响，这是地球系统的一个主要地貌要素。

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.