Understanding the role of Antarctic sea ice in dense water formation and heat and carbon sequestration: from satellite altimetry to 'big data' analysi

海洋是地球系统中最大的碳库，它储存了人类活动产生的90%以上的多余热量。海洋吸收热量和碳的速度在空间和时间上都有很大差异，南大洋是吸收这两种物质的关键区域。然而，我们在预测未来这种情况将如何变化方面的技能有限。冰-海洋-大气的相互作用是决定海洋吸收碳和热的速率的关键。南极海冰的形成/输出和绕极西风是南大洋的主要表面强迫，推动了充满海洋内部大部分的稠密沃茨的上升流和通风，并形成了南极底层水，这是全球深海环流的一个关键组成部分。海冰上的季节性开口--Polynyas --是在南极边缘形成深而密集的陆架沃茨的另一个主要因素。然而，耦合气候模式对南大洋动力学和环流的模拟很差。即使是国家的最先进的模拟未能充分代表冰-海洋-大气的相互作用和地球化学过程，在这些地区的观测是稀缺的和不完整的。MethodsSatellite along-track altimetry data in Antarctic sea ice leads will be used to analyze the ocean's sea level inside polynyas，to identify the fingerprints of dense water formation and circulation.为此，将处理和分析CryoSat-2（欧洲空间局）和ICESat-2（美国航天局）极地卫星飞行任务的海面高度和海面高度异常产品，将在第六次耦合模式相互比较项目（CMIP 6）的最先进模拟中评估南大洋深水形成和环流驱动过程（如风和海冰动力学）的代表性。这将通过建立先进的基于云的计算能力来实现（例如Pangeo），并使用统计工具和机器学习技术来识别和探索冰-海洋-大气过程和相互作用之间的关键关系。这些综合结果将用于确定南极海冰对海洋环流和热量/碳吸收的影响，提高我们对现在和过去趋势的理解，培训2020年，CryoSat-2和ICESat-2的轨道部分对齐，以提供卫星同步测量的独特数据集，并提高南极洲周围海冰测量的准确性。项目工作将包括在美国航天局进行一次国际访问，在那里正在开发ICESat-2海冰数据。此外，CMIP 6模拟档案最近已可供使用，并将为政府间气候变化专门委员会（气专委）第六次评估报告作出贡献，数值建模和卫星遥感方面的这些最新进展使这样一个项目特别及时，而处理和解释这类数据产品的能力是国际环境研究中最需要的技能之一。该博士学位将使学生能够在具有各种专业知识的国际团队的支持下熟练掌握这些技术，包括计算机编程和处理“大数据”档案。该学生将在南安普顿的国家海洋学中心工作，并与该学生注册的利兹大学的主管密切合作，南安普顿大学和英国南极调查局。将有机会参加南极考察巡航。

The ocean is the largest carbon reservoir in the Earth system and it stores over 90% of the excess heat produced by anthropogenic activities. The rate at which both heat and carbon are absorbed by the ocean varies strongly, both in space and time, and the Southern Ocean is a key region for the uptake of both. However, we have limited skills in predicting how this will change in the future. Ice-ocean-atmosphere interactions are key in determining the rates of carbon and heat uptake by the ocean. Antarctic sea ice formation/export and circumpolar westerly winds are the dominant surface forcings in the Southern Ocean, driving the upwelling and ventilation of the dense waters that fill most of the ocean's interior and the formation of Antarctic Bottom Water, a key component of the global abyssal circulation. Polynyas - seasonal openings in the sea ice - are the other main contributors to the formation of deep and dense shelf waters around the Antarctic margins. However, Southern Ocean dynamics and circulation are poorly simulated in coupled climate models. Even state-of-the-art simulations fail to represent both ice-ocean-atmosphere interactions and biogeochemical processes adequately, and observations in these regions are scarce and patchy.MethodsSatellite along-track altimetry data in Antarctic sea ice leads will be used to analyse the ocean's sea level inside polynyas, to identify the fingerprints of dense water formation and circulation. To this end, Sea Surface Height and Sea Height Anomaly products will be processed and analysed from both the CryoSat-2 (European Space Agency) and ICESat-2 (NASA) Polar satellite missions.The representation of processes driving deep water formation and circulation in the Southern Ocean (such as winds and sea ice dynamics) will be assessed in state-of-the-art simulations from the 6th Coupled Model Intercomparison Project (CMIP6). This will be achieved by setting up advanced cloud-based computing capabilities (e.g. Pangeo) and using statistical tools and machine learning techniques to identify and explore the key relationships between ice-ocean-atmosphere processes and interactions.These combined results will be used to determine the effect of Antarctic sea ice on ocean circulation and heat/carbon uptake, improve our understanding of present and past trends, and more skillfully predict how these may change in the future.TrainingThe orbits of CryoSat-2 and ICESat-2 were partially aligned in 2020, to provide a unique dataset of coincident measurements from the satellites and increase the accuracy of sea ice measurements around Antarctica. Project work will include a hosted international visit at NASA, where ICESat-2 sea ice data are being developed. In addition, the CMIP6 archive of simulations has recently become available and will contribute to the 6th assessment report of the Intergovernmental Panel for Climate Change (IPCC).These recent advances in both numerical modelling and satellite remote sensing make such a project especially timely, while the ability to process and interpret these types of data products is among the most in-demand skills in international environmental research. This PhD will enable the student to develop proficiency in these techniques, including computer programming and handling 'big data' archives, with the support of an international team with a diverse range of expertise.The student will be based at the National Oceanography Centre in Southampton and work closely with supervisors based at the University of Leeds, where the student will be registered, the University of Southampton and the British Antarctic Survey. There will be opportunities to participate in Antarctic research cruises.