Advaenced state estimats of the ocean and cryosphere: innovative new tools to better understand, predict, and prepare for sea level changes

海平面上升是当今人类面临的最严重的适应挑战之一。SLR增加了风暴潮、沿海洪水和侵蚀的频率和严重程度，从而破坏了关键基础设施，阻碍了经济活动，并可能使全球居住在沿海社区的1亿多人流离失所。在“一切照旧”的情况下，到2100年，在海平面上升86厘米的情况下，全球洪灾成本可能会增加到每年超过10万亿GB。尽管单反很重要，但对本世纪单反的预测非常不确定。SLR预测中最大的不确定性来源来自西南极冰盖(WAIS)，如果它完全融化，最终有可能使海平面上升3米以上。从南极海岸线伸出的巨大浮动冰架像大坝一样，阻止了WAIS流入海洋和提高海平面。这些关键的冰架正在日益迅速地融化；近几十年来，所有南极冰架的冰层融化速度增加了12倍以上。冰架是非常动态的系统，可以对海洋循环的变化做出快速反应，例如，冰架下面的温水入侵增加会使冰架从下面融化。海平面在中短期内迅速上升的威胁突出表明，需要更好地了解洋流如何将热量输送到脆弱的南极冰架底部。到目前为止，这一领域的进展一直受到与提取详细的热量预算、冰架融化速度和从有限的一组观测中提取敏感性相关的挑战的阻碍。在本次研究金中，我将使用敏感性分析技术(即伴随模型)来建立下一代海洋和冰架模型框架，这将使我们做出可靠和有用的单反预测的能力发生一步变化。我将第一次在一个分级的海冰状态估计框架中结合观测和现实的物理模型，这将使我能够：(1)获得海冰界面融化速率和其他难以观测的参数的空间变化的、观测受限的估计；(2)量化海冰界面的热含量和融化速率对本地和远程气-海相互作用和海洋环流的敏感性；(3)创建空间和时间上的详细的热量预算，以跟踪热量如何从开阔的海洋输送到冰架；以及(4)通过智能地瞄准关键位置进行新的测量，优化未来的观测活动。这一海冰状态估计框架将适用于地球上的任何海冰系统，为我们提供了改变我们理解这些关键海平面调节器当前和未来行为的能力的潜力。因此，全球社会将获得更好的信息，从而能够更好地应对海平面上升，从而降低低洼基础设施、社区和企业面临的风险。

Sea level rise (SLR) is one of the most serious adaptation challenges facing humanity today. SLR increases the frequency and severity of storm surges, coastal flooding, and erosion, thereby damaging critical infrastructure, hampering economic activity, and potentially displacing more than 100 million people globally who live in coastal communities. Under "business as usual" conditions, global flood costs could increase to over £10tn per year by 2100, under 86 cm of sea level rise. Despite its importance, projections of SLR over this century are very uncertain. The greatest single source of uncertainty in SLR projections comes from the West Antarctic Ice Sheet (WAIS), which has the potential to eventually raise sea levels by over three metres if it melts entirely. The WAIS is held back from flowing into the ocean and raising sea levels by large floating ice shelves that protrude from the Antarctic coastline, acting like dams. These crucial ice shelves are melting increasingly rapidly; in recent decades, the rate of ice loss from all Antarctic ice shelves has increased by more than a factor of twelve. The ice shelves are very dynamic systems that can respond quickly to changes in ocean circulation, e.g. increased intrusion of warm water under the ice shelves can melt them from underneath. The threat of rapidly rising seas in the near-to-medium term future highlights the need for improved understanding of how ocean currents deliver heat to the vulnerable undersides of Antarctic ice shelves. Thus far, progress in this area has been hampered by the challenges associated with extracting detailed heat budgets, ice shelf melt rates, and sensitivities from a limited set of observations. In this Fellowship, I will use sensitivity analysis techniques (i.e. adjoint modelling) to establish a next-generation framework for ocean and ice shelf modelling that will make a step change in our ability to make robust and useful SLR projections. I will, for the first time, combine observations and realistic physical models in a hierarchical ocean-ice state estimation framework that will allow me to: (1) obtain spatially-varying, observationally-constrained estimates of melt rates and other hard-to-observe parameters at the ocean-ice interface; (2) quantify the sensitivities of heat content and melt rates at the ocean-ice interface to local and remote air-sea interactions and ocean circulation; (3) create spatially and temporally detailed heat budgets to track how heat is delivered from the open ocean to the ice shelves; and (4) optimise future observing campaigns by intelligently targeting key locations for new measurements. This ocean-ice state estimation framework will be applicable to any ocean-ice system on Earth, offering the potential to transform our ability to understand the present and future behavior of these key sea level regulators. As a result, global societies will be better informed and hence better able to respond to sea level rise, reducing risks to low-lying infrastructure, communities, and businesses.