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

西南极冰盖(WAIS)的崩溃将使海平面上升约3米(10英尺)。因此，关键是要了解WAIS是否会在未来的气候变化下崩溃，如果是的话，会以多快的速度崩溃。要了解冰盖将如何应对人为气候变化，一种方法是了解它对过去暖期的反应。例如，WAIS很有可能在上一次间冰期(13万至11.6万年前)崩溃。这种崩塌被认为是由于靠近冰盖边缘的南大洋变暖造成的，但上一次间冰期的气候与可能导致WAIS崩塌的当地海洋条件之间的关系并未得到很好的理解。此外，海洋必须变暖多少才能引发WAIS的大范围撤退，这一点尚不清楚。该项目将使用新的建模功能来了解WAIS崩溃所需的组合气候和冰盖条件。这一结果将改善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气候和冰盖条件的理解，这些条件可能导致最后一次间冰期(LIG)期间西南极冰盖(WAIS)的崩溃，并确定未来几个世纪是否可能满足崩溃的条件。对LIG南极冰盖的大多数模拟都依赖于有限的一组规定的海洋热通量，并且LIG气候条件与WAIS行为之间的关系几乎完全是在有限或没有冰盖-气候耦合的情况下探索的。该项目将通过社区地球系统模式(CESM2)与社区冰盖模式(CISM)耦合的新的瞬变古气候模拟，以及过去和未来的大型冰盖模拟实验，来探索WAIS坍塌的不确定性。这些实验将首次在CESM中包括与瞬变气候共同演化的南极动态冰盖，以解释与向海洋融化的水通量、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。该团队还将进行大型的仅限CISM的实验，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，该项目将尽可能充分地评估导致WAIS崩溃的气候和冰盖相互作用的条件。这项工作通过使用(1)相对高分辨率的冰盖模型来更好地解决接地线动力学问题，(2)更真实的冰盖-大气和冰盖-海洋耦合，以及(3)更广泛的可能的气候边界条件、次冰架融化参数和冰盖物理来改进以前的工作。

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.