Collaborative Research: Under what Climate Conditions does the West Antarctic Ice Sheet Collapse?

南极西部冰盖（WAIS）的崩塌将使海平面上升约3米（10英尺）。因此，了解WAIS是否会在未来的气候变化下崩溃，以及如果会崩溃，速度有多快，至关重要。了解冰盖如何应对人为气候变化的一种方法是了解它如何应对过去的温暖期。例如，WAIS很可能是在最后一次间冰期（13万至11.6万年前）崩塌的。这种崩塌被认为可以用靠近冰原边缘的南大洋变暖来解释，但是最后一次间冰期的气候和可能导致WAIS崩塌的当地海洋条件之间的关系还没有得到很好的理解。此外，尚不清楚海洋必须变暖多少才能引发大面积的WAIS撤退。该项目将使用新的建模能力来了解WAIS崩塌所需的综合气候和冰盖条件。这些结果将有助于改进对未来几十年和未来几个世纪海平面大幅上升可能性的估计。这项工作旨在促进我们对末次间冰期（LIG）可能导致南极西部冰盖（WAIS）崩塌的气候和冰盖条件的理解，并确定崩塌的条件是否可能在未来几个世纪内满足。大多数南极冰盖的模拟都依赖于一组有限的规定的海洋热通量，并且几乎完全在有限或没有冰盖-气候耦合的情况下探索了LIG气候条件与WAIS行为之间的关系。该项目将通过群落地球系统模式（CESM2）与群落冰盖模式（CISM）耦合的新瞬态古气候模拟，以及过去和未来冰盖模拟实验的大集合，探索WAIS崩塌的不确定性。在CESM中，这些实验将首次包括与短暂气候共同演变的动态南极冰盖，以解释与流入海洋的融水通量、冰架下的海洋变暖以及冰盖地形对区域大气环流的影响有关的反馈。该小组还将进行大规模的cims综合实验，以探索导致WAIS解体的冰盖模型参数和气候边界条件的空间。通过这种方式，该项目将尽可能全面地评估导致WAIS崩塌的相互作用的气候和冰盖条件。这项工作在以前的工作基础上进行了改进，使用了(1)一个相对高分辨率的冰盖模型，可以更好地解析地线动力学；(2)更真实的冰盖-大气和冰盖-海洋耦合；(3)更广泛的可能的气候边界条件、亚冰架融化参数和冰盖物理。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The collapse of the West Antarctic Ice Sheet (WAIS) would raise sea level by about three meters (10 feet). It is therefore critical to understand whether the WAIS will collapse under future climate change, and, if so, how quickly. One way to learn about how the ice sheet will respond to anthropogenic climate change is to understand how it responded to past warm periods. It is very likely, for example, that the WAIS collapsed during the last interglacial period (130,000 to 116,000 years ago). This collapse is thought to be explained by warming of the Southern Ocean near the ice sheet edge, but the relationship between the climate of the last interglacial period and the local ocean conditions that may have led to WAIS collapse is not well understood. In addition, it is unknown how much warmer the ocean must be to trigger widespread WAIS retreat. This project will use new modeling capabilities to understand the combined climate and ice sheet conditions necessary for WAIS collapse. The results will lead to improved estimates of the likelihood of substantial sea-level rise in the next few decades and the coming centuries.This work aims to advance our understanding of the climate and ice sheet conditions that probably led to West Antarctic Ice Sheet (WAIS) collapse during the Last Interglacial (LIG), and to determine whether conditions for collapse are likely to be met in the coming centuries. Most simulations of the LIG Antarctic ice sheet have relied on a limited set of prescribed ocean heat fluxes, and the relationship between LIG climate conditions and the behavior of the WAIS has been explored almost exclusively with limited or no ice sheet-climate coupling. This project will probe WAIS collapse uncertainties through new transient paleoclimate simulations with the Community Earth System Model (CESM2) coupled to the Community Ice Sheet Model (CISM), along with large ensembles of past and future ice-sheet modeling experiments. The experiments will include, for the first time in CESM, a dynamic Antarctic ice sheet co-evolving with a transient climate, to account for feedbacks associated with meltwater fluxes to the ocean, ocean warming under ice shelves, and the influence of ice-sheet topography on the regional atmospheric circulation. The team will also run large ensembles of CISM-only experiments to explore the space of ice-sheet model parameters and climate boundary conditions that lead to WAIS disintegration. In this way, the project will evaluate as fully as possible the interacting climate and ice-sheet conditions that lead to WAIS collapse. This work improves on previous work by using (1) a relatively high-resolution ice-sheet model that better resolves grounding-line dynamics, (2) more realistic ice-sheet-atmosphere and ice-sheet-ocean coupling, and (3) a wider range of possible climate boundary conditions, sub-ice-shelf melting parameters, and ice-sheet physics.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.