NSFGEO-NERC Paleoclimate signatures of the climate response to West Antarctic ice sheet collapse

在古气候和冰川学研究中，一个主要的悬而未决的问题是，西南极冰盖（WAIS）是否在末次间冰期（海洋同位素阶段（MIS）5e）约130 ~116 ka之间崩塌。有确凿的证据表明WAIS在过去70万年内的某个时刻崩溃（谢勒等人，1998年），但在特定时间WAIS崩溃的证据要么是间接的（和模棱两可的）或不足以限制时间和规模（Joughin和Alley，2011年）。缺乏知识的时间和速度WAIS崩溃在过去阻碍了我们的能力，以验证模型的潜在WAIS崩溃的未来。美国国家科学院最近的一份报告确定了这个问题-以前WAIS崩溃的速度和时间，特别是MIS 5e期间是否发生崩溃-作为极地研究战略投资的首要任务（Polar Research Board，（2015年）通过气候系统对这种崩溃的反应的证据，有可能限制过去WAIS崩溃的速度和时间。崩溃这一想法与寻找前冰构造的冰川地质证据（例如，Naish等人，2009年），或从海平面记录推断冰盖大小。相反，这里的想法是，冰盖大小的显著变化将导致大气和海洋环流的变化，这些变化记录在古气候档案中，如冰芯，洞穴沉积物或海洋和湖泊沉积物。最近的模拟工作表明，对WAIS崩溃的气候响应可能包括以下内容（Justino等人，2015; Steig等人，2015; Singh等人，出版中;霍洛威等人，审查中）：- AMOC的变化（大西洋纬向翻转环流）-ITCZ向北移动（热带辐合带）-南极洲，包括南极洲以外地区降水中温度和18 O比值的变化这些气候响应不是融水强迫的结果。（尽管这也很重要），而是由于南极冰盖形态的重大变化导致大气环流的变化。冰盖形态影响大气环流并不是一个新概念;已经有许多研究证明了Laurentide和Fennoscandian冰盖的这一点（例如，Kutzbach和Guetter，1986年; Roe和Lindzen，2001年）。但是，认为南极冰盖在以前的间冰期可能发生的相对较小的变化（以及未来可能发生的人为气候强迫）的想法是新颖的，值得进一步探索。这是这里提出的工作的基础。

A major unanswered question in paleoclimate and glaciological research is whether the West Antarctic ice sheet (WAIS) collapsed during the last interglacial period, Marine Isotope Stage (MIS) 5e, between ~130 and ~116 ka. There is solid evidence for WAIS collapse at some point within the last 700,000 years (Scherer et al., 1998), but the evidence for WAIS collapses at specific times is either indirect (and equivocal) or is insufficient to constrain the timing and magnitude (Joughin and Alley, 2011). Lack of knowledge of both the timing and rate of WAIS collapse in the past hampers our ability to validate models of potential WAIS collapse in the future. A recent report of the U.S. National Academy of Sciences identified this question - the rate and timing of previous WAIS collapses, and particularly whether collapse occurred during MIS 5e - as a top priority for strategic investments in polar research (Polar Research Board, 2015).It may be possible to constrain both the rate and timing of WAIS collapse in the past through evidence of the response of the climate system to that collapse. This idea is distinct from that of looking for glacial-geological evidence of former ice configurations (e.g., Naish et al., 2009), or inferring ice sheet size from sea level records. Instead, the idea here is that significant changes in ice sheet size will cause changes in atmospheric and ocean circulation that are recorded in paleoclimate archives such as ice cores, speleothems, or marine and lake sediments. Recent modeling work shows that the climate responses to WAIS collapse likely include the following (Justino et al., 2015; Steig et al., 2015; Singh et al., in press; Holloway et al., in review): - changes in AMOC (Atlantic meridional overturning circulation) - a northward shift in the ITCZ (intertropical convergence zone) - changes in temperature and 18O ratios in precipitation over Antarctica, including areas outside the region of collapseThese climate responses are not the consequences of meltwater forcing (though this may also be important), but instead are owing to changes in atmospheric circulation resulting from the significant changes in the morphology of the Antarctic ice sheet. That ice sheet morphology affects atmospheric circulation is not a new concept; there have been many studies demonstrating this for the Laurentide and Fennoscandian ice sheets (e.g., Kutzbach and Guetter, 1986; Roe and Lindzen, 2001). But the idea that the comparatively small changes in the Antarctic ice sheet that may have occurred during previous interglacial periods (and that may occur in the future in response to anthropogenic climate forcing) is novel, and deserves further exploration. This is the basis of the work proposed here.