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

极地地区在应对气候变化方面最为敏感，并主持着推动这种变化的关键进程。然而，这些地区是人们所知最少的地区，部分原因是历史上观测的匮乏。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。建立海洋与冰冻圈相互作用的模型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与英国气象局IPCC级气候模型HadGEM的最新发展结合起来。它将讨论IPCC模型对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。相对温暖的海洋与浮冰架的相互作用可能会加速南极冰盖的融化，导致海平面上升。海冰融化和冰架融化都会导致大陆架的新生。随后的海冰形成导致盐度增加，从而增加密度。这些水团转化过程产生了密集的冷流出物，成为南极底层水。这些过程即使在涡旋分辨的海冰模型中也表现得很差;在气候模型中，这些过程是次网格尺度的，必须参数化。该项目有两个方面。首先，学生将研究南大洋和南极大陆架的IPCC气候模型的模拟，这是一个验证不足的地区。学生将量化水团特性的表现，并评估模型和观测场中密集水的形成位置和方式。观测数据将包括南半球水文剖面图和南半球海洋观测系统的全年系泊，南半球海洋观测系统是一个国际极地年项目，在南极大陆架和陆坡上有一个密集的实地阶段（2008-2010年）。这将有助于评估环极和季节性水团特征。再往北，我们将利用Argo浮标对南大洋上2000米的覆盖范围。第二个方面将涉及学生在HadGEM的新发展的评价。一个冰架模型正在被纳入HadGEM，作为更广泛的模型开发的一部分，以将相互作用的冰盖与海洋和大气耦合起来。这取决于经过充分验证的参数化，以将温暖的中层沃茨水输送到冰架底部，因此模型水团的验证将直接影响到这方面。学生将评估海洋与冰架相互作用的过程，包括温暖的中层沃茨涌上大陆架和冰架融水对海洋的影响。对于学生来说，这是一个难得的机会，可以参与评估主要气候模型之一的实质性升级，以及随之而来的海洋和大气成分是否得到“改善”。学生将接受处理大型数据集的培训;计算机编程;数值建模和海洋/气候动力学。他们将参加南大洋研究巡航，学习海洋学观测技术和数据质量控制。他们将受益于参与国际小岛屿发展中国家战略项目的综合阶段，包括参加讲习班和会议。所有UEA博士生参加可转移技能培训。该项目通过用新的观测结果验证气候模型的发展而使气象局受益。学生通过与那些正在开发和运行下一代IPCC气候模型的人密切合作而获益。

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.