The Ice-Covered Ocean: the Final Challenge for Climate Models?

冰雪覆盖的海洋：气候模型的最后挑战？

• 批准号: NE/I018239/1
• 负责人: Karen J. Heywood
• 金额: $ 9.48万
• 依托单位: University of East Anglia
• 依托单位国家: 英国
• 项目类别: Training Grant
• 财政年份: 2011
• 资助国家: 英国
• 起止时间: 2011 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FI018239%2F1
• 关键词: Ice; Covered; Ocean; Final; Challenge

The polar regions are most sensitive in responding to climate change, and host key processes driving that change. Yet they are the regions where least is known, in part because of the historical paucity of observations. Climate models also find the high latitudes particularly challenging, where length-scales of ocean processes are much smaller than at low latitudes. Modelling the interaction of ocean and cryosphere is an active area of research. This project brings together new observations in the Southern Ocean and around Antarctica with the latest developments in the UK Met Office's IPCC-class climate model HadGEM. It will address how well the IPCC models perform against ocean measurements, and assess the climate impacts of the new ice shelf model being implemented in HadGEM. Melting of the Antarctic ice sheet may be accelerated by interaction of the relatively warm ocean with floating ice shelves, contributing to sea level rise. Both sea ice melt and ice shelf melt cause a freshening on the continental shelf. Subsequent sea ice formation causes an increase in salinity and hence density. These water mass transformation processes create the dense, cold outflow that becomes Antarctic Bottom Water. These processes are poorly represented even in eddy-resolving ocean-ice models; in climate models these processes are sub-gridscale and must be parameterised. The project has two aspects. First, the student will study simulations from the available IPCC climate models of the Southern Ocean and Antarctic shelf, a poorly validated region. The student will quantify how well the water mass properties are represented, and assess where and how dense water forms in the models and observational fields. Observational data will include the meridional hydrographic sections and year-long moorings of SASSI, an International Polar Year project with an intensive field phase (2008-2010) on the Antarctic continental shelf and slope. This will enable assessing circumpolar and seasonal water mass characteristics. Further north, we will exploit the coverage of the upper 2000 m of the Southern Ocean from Argo floats. The second aspect will involve the student in appraisal of a new development of HadGEM. An ice shelf model is being included in HadGEM, as part of a broader model development to couple interactive ice sheets to the oceans and atmosphere. This depends on well validated parameterisations to transport warm mid-depth waters to the base of the ice shelves, so the validation of model water masses will feed directly into this aspect. The student will assess the processes of interaction of ocean with ice shelves, both the upwelling of warm mid-depth waters onto the continental shelf and impact of ice shelf melt water on the ocean. This is a rare opportunity for a student to be involved in assessing a substantial upgrade to one of the major climate models, and whether the consequent ocean and atmosphere components are 'improved'. The student will be trained in handling large datasets; computer programming; numerical modelling and ocean/climate dynamics. They will participate in a Southern Ocean research cruise to learn observational oceanographic techniques and data quality control. They will benefit from embedding in the synthesis phase of the international SASSI project, including attending workshops and conference sessions. All UEA PhD students attend transferable skills training. This project benefits the Met Office through the verification of climate model developments with new observations. The student gains by working closely with those who are developing and running the next generation of IPCC climate models.

极地地区是应对气候变化最敏感的地区，也是推动气候变化的关键过程的发源地。然而，这些地区是最不为人所知的地区，部分原因是历史上缺乏观测。气候模型还发现高纬度地区特别具有挑战性，那里的海洋过程的长度尺度比低纬度地区小得多。模拟海洋和冰冻圈的相互作用是一个活跃的研究领域。该项目将南大洋和南极洲周围的新观测结果与英国气象局IPCC级气候模型HadGEM的最新进展结合在一起。它将讨论IPCC模型相对于海洋测量的表现如何，并评估HadGEM正在实施的新冰架模型的气候影响。相对温暖的海洋与漂浮的冰架相互作用，可能会加速南极冰盖的融化，从而导致海平面上升。海冰融化和冰架融化都会导致大陆架的清新。随后的海冰形成导致盐度的增加，从而导致密度的增加。这些水团转化过程形成了密集、寒冷的外流，形成了南极底层水。即使在涡旋分辨的海冰模式中，这些过程也表现得很差；在气候模型中，这些过程是亚网格尺度的，必须进行参数化。该项目有两个方面。首先，这名学生将研究IPCC现有的南大洋和南极大陆架气候模型的模拟，这是一个验证效果不佳的地区。学生将量化如何很好地表示水团性质，并评估在模型和观测领域中哪里以及如何形成致密水。观测数据将包括SASSI的经向水文剖面和一年的系泊情况，这是一个国际极地年项目，在南极大陆架和斜坡上有密集的实地阶段(2008-2010年)。这将使评估绕极和季节性水团特征成为可能。再往北，我们将利用阿尔戈浮标对南大洋上层2000米的覆盖。第二个方面将让学生参与对HadGEM的新发展的评估。HadGEM正在包括一个冰架模型，作为将交互冰盖与海洋和大气耦合的更广泛模型开发的一部分。这依赖于经过充分验证的参数，以将温暖的中深水输送到冰架底部，因此对模型水团的验证将直接影响到这一方面。学生将评估海洋与冰架相互作用的过程，包括温暖的中深水上升到大陆架上，以及冰架融化水对海洋的影响。对于学生来说，这是一个难得的机会，可以参与评估一个主要气候模型的实质性升级，以及由此产生的海洋和大气成分是否得到了“改善”。学生将接受处理大型数据集、计算机编程、数值建模和海洋/气候动力学方面的培训。他们将参加南大洋研究游轮，学习观测海洋学技术和数据质量控制。他们将受益于融入国际SASSI项目的综合阶段，包括参加讲习班和会议。所有UEA博士生都参加了可转让技能培训。该项目通过用新的观测资料核实气候模型的发展，使气象局受益。学生通过与开发和运行下一代IPCC气候模型的人密切合作而受益。