The ice age, oceans and climate: triggers of iceberg calving and rapid temperature change

这个博士项目将使用数值模拟来建立发生在最后一次冰川消融早期的复杂事件链，将灾难性的冰盖崩塌、冰山舰队、快速冷却、突然变暖和大规模大西洋环流的完全重组联系起来。该候选人将探索连接地球系统这些不同部分的可能机制，进行高调的研究，检验现有的假设，并创造新的假设，以了解高纬度地区快速气候变化的原因和后果。背景：在末次盛冰期（21000年前），巨大的冰盖覆盖了北半球的大部分地区，覆盖了北美洲、格陵兰岛和欧亚大陆的大片地区。随着气候变暖，冰盖开始消退，北大西洋引发了一系列有趣的事件。大规模海洋环流减缓，气候变冷，冰山群被释放，海洋环流迅速加强，气温突然上升。尽管有详细的文献记载（海因里希第一次事件、海因里希第一次事件、博林变暖），但这些事件究竟是如何联系的，甚至是否联系在一起，仍不得而知。最近的两项研究提出了一个尝试性假设，即欧亚冰盖的融化导致海洋环流减缓，北大西洋地区降温，并引发欧亚冰盖上的冰山崩解加剧。这放大了最初的变化，增加了来自北美的冰山产量，并维持了冷却。但是，这一系列事件从未被验证过。此外，目前尚不清楚是什么导致了最后这些事件；突然的博林变暖是流入海洋的融水数量迅速减少吗？大气中二氧化碳含量是否越过了临界阈值？或者这仅仅是一个固有的不稳定的气候制度的结果？最后一次消冰期是有记录的气候突变的最好时期，然而我们不明白记录的事件是如何以及为什么发生的。这个令人兴奋的项目解决了这一挑战，测试了冰-海洋-大气的相互作用，从而产生了有关气候的开创性新知识。申请前请联系主管（r.ivanovic@leeds.ac.uk）获取更多信息。项目目标：该候选人将运行复杂的数值气候和冰盖模型，以研究末次冰期早期（21- 145000年前）气候、冰山和海洋环流之间的相互作用。总体目标是建立围绕海因里希事件1的事件链，包括冰盖融化、大规模大西洋环流（大西洋经向翻转环流，AMOC）的快速放缓、北大西洋变冷、欧亚和北美冰盖冰山排放增强（海因里希事件1）、AMOC的恢复和突然变暖（博林变暖）。

This PhD project will use numerical modelling in order to establish the complex chain of events that took place early in the last deglaciation, linking catastrophic ice sheet collapse, iceberg armadas, rapid cooling, abrupt warming and the complete reorganisation of largescale Atlantic Ocean circulation. The candidate will explore possible mechanisms that link these different parts of the earth system, undertaking high profile research to examine existing hypotheses and create news ones to understand the cause and consequences of rapid climate change in the high latitudes.BACKGROUNDAt the Last Glacial Maximum (21,000 years ago), vast ice sheets stretched across much of the Northern Hemisphere, covering large expanses of North America, Greenland and Eurasia. As climate warmed, and the ice sheets began retreating, an intriguing chain of events was triggered in the North Atlantic. Largescale ocean circulation slowed, climate cooled, armadas of icebergs were released, ocean circulation rapidly strengthened and temperatures abruptly rose. Although well documented individually (Heinrich Stadial 1, Heinrich Event 1, the Bolling Warming), it remains unknown precisely how and even if these events were linked. Two recent studies put forward the tentative hypothesis that melting of the Eurasian ice sheet caused ocean circulation to slow-down, cooling the North Atlantic region and triggering enhanced iceberg calving from the Eurasian ice sheet. This amplified the initial change, increasing iceberg production from North America and sustaining the cooling. But, this chain of events has never been tested. Furthermore, it remains unclear what caused the last of these events; the abrupt Bolling Warming. Was it a rapid reduction in the amount of meltwater reaching the ocean? Was a critical threshold in atmospheric CO2 crossed? Or was it simply the result of an inherently unstable climate regime? The last deglaciation is the best documented period of abrupt climate change, yet we do not understand how and why the recorded events took place. This exciting project tackles this challenge, testing ice-ocean-atmosphere interactions to produce seminal new knowledge of our climate.Please contact the lead supervisor (r.ivanovic@leeds.ac.uk) for more information and before applying.PROJECT AIMThe candidate will run complex numerical climate and ice sheet models to examine the interplay between climate, icebergs and ocean circulation in the early period of the last deglaciation (21-14.5 thousand years ago). The overall aim is to establish the chain of events surrounding Heinrich Stadial 1, involving ice sheet melting, a rapid slowdown of the largescale Atlantic Ocean circulation (Atlantic Meridional Overturning Circulation, AMOC), North Atlantic cooling, enhanced iceberg discharge from the Eurasian and North American ice sheets (Heinrich Event 1), a resumption of the AMOC and abrupt warming (Bolling Warming).