南极普里兹湾海冰季节性变化的高分辨率数值模拟

Fine-scale simulation of the seasonal variations of sea ice cover in the Prydz bay,Antarctic

普里兹湾海冰以一年冰为主,海冰覆盖存在较大的季节性变化。海冰的分布及其季节性变化主要受当地大气环流及海流的影响。基于一个海洋-海冰耦和模式,模拟研究了该海区海冰的季节性变化特征。海洋模式基于MIT环流模式(MITgcm),海冰动力学模式参考Hibler类型的VP模型,热力学过程取自Winton三层模型。模式区域覆盖整个普里兹湾(75°～55°S,50°～100°E),水平分辨率为(1/6)°×(1/12)°,垂向为50层。大气强迫场选用每6 h一次的NCEP再分析资料。模拟的海冰范围季节性变化与遥感资料拟合较好。每年的3～8月份,普里兹湾海冰快速生长,9～10月份达到最大值,随后海冰开始融化,2月份达到最小值。从9月份开始,受大陆沿岸局地风场的影响,在模拟区域范围内,形成了3个典型的沿岸冰间湖。和观测资料对比,模式较好地捕捉到了3个典型冰间湖的时间及空间分布。沿岸地形及海流对海冰厚度的分布具有重要影响,在西向沿岸流及西冰架地形的影响,在地形的上游形成海冰堆积,厚度最大超过3 m。同时,在下游方向,沿66°S形成一个厚冰带。

Prydz Bay is almost partially covered by sea ice all year.The distribution of sea ice and its annual variation are controlled mainly by the meteorological conditions and ocean currents.To model the seasonal variation of sea ice,a coupled ice-ocean model has been developed.The ocean model based on the MITgcm,and the ice model is based on the viscous-plastic rheology of Hibler and Winton three-layer reformulated thermodynamics.The model domain encompasses Prydz Bay（75°～55°S,50°～100°E,） and with a grid resolution of（1/6）°×（1/12）° degree（latitude/longitude,average 6 km）.Forcing fields are computed from 6-hourly NCEP reanalysis.The main features of the model simulations include an increasing ice cover from March to August,an approximately constant ice cover from August to November and a decreasing ice cover from November to February.In mid-September,polynyas start to develop at three coastal regions,temporal and spatial characteristics of the three polynyas are well reproduced and compare with available satellite data.Thick ice up to 3 m is piled up at the east end of the West Ice Shelf due to westward alongcoast current.