Collaborative Research: Resolving Earth Structure Influence on Ice-Sheet Stability in the Wilkes Subglacial Basin (RESISSt)

第一部分：非技术性地球气候变暖有可能导致全球冰川和冰盖大范围崩塌，推动全球海平面上升。了解这种变化的速度和程度对于预测未来的海平面以及它将如何影响基础设施和财产至关重要。南极洲冰盖的崩塌有可能使全球海平面上升60米。然而，并不是南极洲的所有地区都同样有可能崩溃。南极洲东部的威尔克斯冰下盆地是一个有可能崩溃的地区，这个地区的面积是加利福尼亚州中央山谷的两倍。地质证据表明，由于过去的全球变暖事件，该地区的冰盖已经显著后退。虽然地质记录清楚地表明该地区的冰盖是脆弱的，但未来任何退缩的速度和规模都将受到该地区地质的重大影响。特别是，在气候变暖的过程中，位于温暖地球上方的冰盖将更快地崩塌。限制威尔克斯冰下盆地冰盖稳定性的地质控制仍然具有挑战性，因为冰盖隐藏了数公里厚的冰下的地质。作为了解威尔克斯冰下盆地未来冰消失可能性的一个步骤，该项目将对现有数据进行地球物理分析，以更好地约束该地区的地质情况。这些结果将限制旨在理解控制该地区冰盖行为的构造的新模型。这些新的模型将突出对威尔克斯冰下盆地冰盖的未来施加最重大控制的地质特性。这种洞察力对于指导未来旨在收集更充分地限制南极洲未来海平面潜力所需的现场观测的努力至关重要。第二部分：技术说明在极地环境中，向内倾斜的海洋盆地容易受到一种称为海洋冰盖不稳定性(MISI)的效应的影响：由温暖的海水从下方侵蚀冰架而造成的失控冰流排水。冰盖响应的大小和时间尺度很大程度上取决于冰床界面的物理条件，而冰床界面的物理条件在很大程度上受盆地构造演化的控制。地形、沉积学、地热通量和地幔粘度都对冰盖的稳定性起着关键作用。然而，在大多数情况下，这些易受MISI影响的地区的固体地球参数在很大程度上是未知的。东南极洲的威尔克斯冰下盆地是一个对MISI有潜在敏感性的地区。该项目将对威尔克斯冰下盆地进行综合调查，将地球物理分析与地幔流动和冰盖模型结合起来，以了解该地区冰盖的稳定性以及相关的潜在海平面上升。这项工作将集中于四个主要目标：(1)根据现有的地震观测以及现有的地球物理和地质数据，建立一个改进的区域构造模型；(2)使用新的构造模型和地震数据来估计上地幔的热、密度和粘性结构，并为WSB绘制热流图；(3)基于密度和粘性约束，模拟地幔流动和评估古地形；以及(4)通过模拟(A)过去的冰盖稳定性使用我们的古地形估计和(B)未来的冰盖稳定性使用我们的热流和地幔粘度估计来评估冰盖行为。最终，该项目将生成WSB下地球物理结构的改进图像，使我们能够评估该地区的地球动力学起源，并评估地质参数对过去、现在和未来冰盖行为的影响。这些努力将突出应该是未来地球物理部署重点的地区和地球物理特性。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Part I: NontechnicalEarths warming climate has the potential to drive widespread collapse of glaciers and ice sheets across the planet, driving global sea-level rise. Understanding both the rate and magnitude of such changes is essential for predicting future sea-level and how it will impact infrastructure and property. Collapse of the ice sheets of Antarctica has the potential to raise global sea-level by up to 60 meters. However, not all regions of Antarctica are equally suspectable to collapse. One area with potential for collapse is the Wilkes Subglacial Basin in East Antarctica, a region twice the size of California's Central Valley. Geologic evidence indicates that the ice-sheet in this region has retreated significantly in response to past global warming events. While the geologic record clearly indicates ice-sheets in this area are vulnerable, the rate and magnitude of any future retreat will be influenced significantly by geology of the region. In particular, ice-sheets sitting above warm Earth will collapse more quickly during warming climate. Constraining the geologic controls on the stability of the ice-sheets of the Wilkes Subglacial Basin remains challenging since the ice-sheet hides the geology beneath kilometers of ice. As a step in understanding the potential for future ice loss in the Wilkes Subglacial Basin this project will conduct geophysical analysis of existing data to better constrain the geology of the region. These results will constrain new models designed to understand the tectonics that control the behavior of the ice-sheets in the region. These new models will highlight the geological properties that exert the most significant control on the future of the ice-sheets of the Wilkes Subglacial Basin. Such insights are critical to guide future efforts aimed at collecting in-situ observations needed to more fully constrain Antarctica's potential for future sea-level. Part II: Technical DescriptionIn polar environments, inward-sloping marine basins are susceptible to an effect known as the marine ice-sheet instability (MISI): run-away ice stream drainage caused by warm ocean water eroding the ice shelf from below. The magnitude and time-scale of the ice-sheet response strongly depend on the physical conditions along the ice-bed interface, which are, to a first order, controlled by the tectonic evolution of the basin. Topography, sedimentology, geothermal heat flux, and mantle viscosity all play critical roles in ice-sheet stability. However, in most cases, these solid-Earth parameters for regions susceptible to the MISI are largely unknown. One region with potential susceptibility to MISI is the Wilkes Subglacial Basin of East Antarctica. The project will provide an integrated investigation of the Wilkes Subglacial Basin, combining geophysical analyses with both mantle flow and ice-sheet modeling to understand the stability of the ice sheet in this region, and the associated potential sea level rise. The work will be focused on four primary objectives: (1) to develop an improved tectonic model for the region based on existing seismic observations as well as existing geophysical and geological data; (2) to use the new tectonic model and seismic data to estimate the thermal, density, and viscosity structure of the upper mantle and to develop a heat flow map for the WSB; (3) to simulate mantle flow and to assess paleotopography based on our density and viscosity constraints; and (4) to assess ice-sheet behavior by modeling (a) past ice-sheet stability using our paleotopography estimates and (b) future ice-sheet stability using our heat flow and mantle viscosity estimates. Ultimately, the project will generate improved images of the geophysical structure beneath the WSB that will allow us to assess the geodynamic origin for this region and to assess the influence of geologic parameters on past, current, and future ice-sheet behavior. These efforts will then highlight areas and geophysical properties that should be the focus of future geophysical deployments.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.