What ends an Interglacial? Feedbacks between tropical rainfall, Atlantic climate and ice sheets during the Last Interglacial (EndLIG)

目前的间冰期将在何时以及如何结束仍然是一个悬而未决的问题。由于气候相对广为人知，最后一次间冰期(LIG)及其之后的冰川开始可以揭示导致新冰期建立的气候机制。已知的终止LIG的一系列气候事件引发了两个关键问题：(1)由于活跃的温盐环流(THC)而延长的间冰期北大西洋温暖是有利于还是推迟了北部冰盖的增长？(2)南美洲湿度的重组是否有助于延长北大西洋的温暖，因为在LIG结束时保持了盐度较高的北大西洋和活跃的THC，正如在冰川时期观察到的热带湿度反馈所表明的那样？为了解决这些问题，我们建议将新的古气候重建与气候模型实验相结合。首先，我们将通过在海洋沉积物岩心的横断面上应用互补的代理来重建南美雨带在最后一次冰川开始期间的详细演化。其次，我们将通过比较热带大西洋表层盐度和深水特性与模式敏感性试验来评估热带水文变化对热带大西洋海面盐度(SSS)和大西洋THC的影响。最后，我们将为最后一次冰川开始运行一个瞬变气候/冰盖模式，并进行一项敏感性研究，在该模式中，将施加不同的海洋热通量，以调查北大西洋持续变暖对冰盖生长的影响。

When and how the present interglacial will end remains an open question. With a relatively wellknown climate, the Last Interglacial (LIG) and following glacial inception can shed some light on the climate mechanisms leading to the establishment of a new ice age. Two key questions arise from the chain of climate events known to end the LIG: (1) Did the interglacial North Atlantic warmth, prolonged by an active thermohaline circulation (THC), favor or delay the growth of northern ice sheets? (2) Did reorganizations in South American moisture contribute to prolong the North Atlantic warmth by maintaining a salty North Atlantic and active THC at the end of the LIG, as suggested by tropical moisture feedbacks observed during glacial times? To address these questions, we propose here to combine new paleoclimate reconstructions with climate model experiments. First, we will reconstruct the detailed evolution of the South American rainbelt during the last glacial inception, by applying complementary proxies on a transect of marine sediment cores. Second, we will assess the impact of tropical hydrologic changes on tropical Atlantic sea surface salinities (SSS) and the Atlantic THC, by comparing tropical Atlantic SSS and deep-water properties with model sensitivity experiments where we will vary the tropical freshwater forcing. Finally, we will perform a transient climate/ice-sheet model run for the last glacial inception, and a sensitivity study, in which different ocean heat fluxes will be imposed to investigate the effect of prolonged North Atlantic warmth on ice sheet growth.