Fragmentation and melting of the seasonal sea ice cover

近年来，北极海冰的夏季面积迅速减少。这些变化改变了当地气候，影响了航行、石油勘探、野生动物和当地社区，气候模型预测，这些变化将对包括欧洲西北部在内的低纬度地区的天气和气候产生重大影响。在冬季，北冰洋的海冰覆盖是由连锁的漂浮海冰组成的马赛克，大部分是冻结在一起的，典型的宽度为10-2000m，厚度为0.1-5m。在夏天，浮冰会融化。在气候模型中，海冰的表示将所有浮冰都视为相同大小，大约300米。这种简化特别有可能影响冰覆盖边缘区域（称为边缘冰带）和冰群最大部分的模式模拟：季节性冰带，即每年夏天融化的区域。这是因为这些地区受海浪的影响更大，海浪可以打破冰层，形成更小的浮冰。浮冰体积的减小影响了冰盖对入射海浪的响应，并促进了侧向融化。当海洋变暖时，较小的浮冰会加速横向融化，加速夏季海冰的退缩。目前气候模型中缺少浮冰破碎过程，本项目将评估其对冰-气候反馈的贡献，相对于表面融化。博士研究生将(i)研究控制季节性和边缘冰区浮冰大小分布的因素；（ii）在气候海冰模式中检验侧向融化；（三）在一个耦合气候模式下检验侧向融化的影响。这个项目汇集了雷丁大学气象系极地观测和建模中心的海冰物理和建模专家，以及气象局哈德利中心的气候模型专家。学生将与两个小组密切合作。

Recent years have seen a rapid reduction in the summer extent of Arctic sea ice. These changes have altered the local climate, affected navigation, oil exploration, wildlife and local communities, and are predicted by climate models to have significant implications for the weather and climate at lower latitudes, including NW Europe. In winter, the sea ice cover of the Arctic Ocean comprises a mosaic of interlocking floating sea ice floes, mostly frozen together, with typical widths of 10-2000m, and thicknesses of 0.1-5m. In summer, the floes can melt apart. The representation of sea ice in climate models treats the floes as all being of the same size, around 300m. This simplification is particularly likely to affect model simulations in the edge region of the ice cover (known as the marginal ice zone) and in the largest part of the ice pack: the seasonal ice zone, which is the region that melts away every summer. This is because these regions are more strongly affected by ocean waves, which can break up the ice cover to create smaller floes. The reduction in floe size affects the response of the ice cover to incoming ocean waves and promotes lateral melting. Smaller floes have an enhanced lateral melt when ocean the ocean is warm, accelerating summer sea ice retreat. The process of floe breakup is currently absent from climate models, and its contribution to ice-climate feedbacks, relative to surface melt, will be evaluated in this project. The PhD student will (i) examine the factors controlling the floe size distribution in the seasonal and marginal ice zone; (ii) examine lateral melt in a climate sea ice model; and (iii) examine the impact of lateral melting a coupled climate model.This project brings together experts in sea ice physics and modelling at the Centre for Polar Observation and Modelling in the department of Meteorology at the University of Reading with experts in climate models at the Met Office Hadley Centre. The student will work closely with both groups.