Modeling Glacial Lake Washburn - Insight into the LGM

非技术性项目描述南极麦克默多干旱河谷沿岸泰勒河谷古代湖面波动的地质现场证据与罗斯冰盖在最后一次冰川盛期(24,000至13,000年前)期间和之后进入河谷河口的进退(湖面较高)和(较低湖面)有关。古老的湖泊记录提供了一些最完整的陆地地质证据，表明南极冰盖在最近一次两极冰川的高度发生了变化。对地质沉积的不同解释导致了两种不同的假设，即罗斯冰盖在最后一次冰盛期向内陆推进了多远，从而产生了高湖面。一种假设认为，进入山谷的有限冰层与较大的湖泊有关，而另一种假说则表明，较大范围的冰川增加与较小的湖泊相关(五倍)。局部冰层推进的范围对罗斯冰盖的整体大小及其对海平面的影响有一定的影响。这个项目将通过模拟形成不同大小湖泊的环境条件来解决不同的解释，并假设更有可能出现其中一个湖泊大小。此外，该团队将发现在平均气温比今天低得多的情况下形成和维持大型湖泊的环境条件，这一观察结果得不到现代观测的支持。麦克默多干谷湖泊水位变化的地貌记录将用于推断末次冰川盛期(LGM)期间的环境条件，提供距今24,000年至约13,000年的11,000年期间的气候记录。在此期间值得注意的事件包括全球海平面末次盛期结束，随后海平面迅速上升，以及两次海平面突然上升，其中包括融水脉冲1A。具体地说，该项目将模拟泰勒山谷的冰川沃什伯恩湖的湖面变化，该湖是该地区有最好记录的古湖泊。它的水平在千禧年的时间尺度上发生了根本性的变化(100s M)，提供了一个强烈的环境变化信号。为泰勒山谷目前的气候和冰川环境开发的已建立的能量平衡模型将根据末次冰川条件进行调整，以使用估计的古环境条件来模拟古湖泊水平，其中包括已知的-4至-8摄氏度的大气凉爽。为了确定导致相同湖面的合理环境条件的范围(不确定性)，采用了蒙特卡罗方法。这一结果将为过去南极气候提供一个新的视角，并有助于关于南极海平面上升的来源的辩论。该项目将为一名博士生提供培训。

Non-technical Project DescriptionGeologic field evidence of ancient lake level fluctuations in coastal Taylor Valley in the McMurdo Dry Valleys of Antarctica has been related to advances (higher lake levels) and retreats (lower lake levels) of the Ross Ice Sheet into the valley mouth during and since the last Glacial Maximum (24,000 to 13,000 years ago). The ancient lake record provides some of the most complete terrestrial geologic evidence of inferred Antarctic ice-sheet changes at the height of the most recent bipolar glaciation. Different interpretations of geologic deposits have led to two alternate hypotheses about how far inland the Ross Ice Sheet advanced to produce high lake levels during the Last Glacial Maximum. One hypothesis suggests that limited ice advances into the valley were associated with larger lakes, whereas the alternative suggests that more extensive ice advances were associated with much smaller lakes (by five times). The local extent of ice advances has implications for the overall size of the Ross Ice Sheet and its impact on sea level. This project will resolve the different interpretations by modeling the environmental conditions under which different sized lakes would form, with the hypothesis that one of the lake sizes would be more likely to occur. In addition, the team will discover the environmental conditions that allow large lakes to form and be maintained when average air temperatures were much colder than today, an observation not supported by modern observations. Technical Project DescriptionA geomorphic record of lake level change in the McMurdo Dry Valleys will be used to infer environmental conditions during the Last Glacial Maximum (LGM) providing a climatic record over an 11,000-year period from 24,000 to about 13,000 years before present. Notable events during this period include the termination of the LGM global sea level low-stand, subsequent rapidly rising sea levels, and two episodes of abrupt sea level rise including meltwater pulse 1A. Specifically, the project will model lake level changes of Glacial Lake Washburn in Taylor Valley, the best documented paleo-lake in the region. Its level changed radically (100s m) over millennial time scales providing a strong signal of environmental change. Established energy balance models developed for the current climate and glaciological setting in Taylor Valley will be adapted to LGM conditions to model paleo-lake levels using estimated paleo-environmental conditions that include an atmosphere known to be cooler by -4 to -8 degrees Celsius. To define the range (uncertainty) of plausible environmental conditions that result in the same lake level a Monte Carlo-style approach is adopted. The results will provide a new perspective on past Antarctic climate and contribute to the debate on Antarctic sources to sea level rise. The project will provide training for a Ph.D. student.