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Ice albedo feedback on sea ice/ocean coupled system

海冰/海洋耦合系统的冰反照率反馈

基本信息

批准号：
12640414
负责人：
OHSHIMA Kay I.
金额：
$ 2.24万
依托单位：
HOKKAIDO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12640414/
关键词：
shortwave radiation seasonal ice zone sea ice melting heat budget Antarctic Ocean ice-ocean coupled system ocean mixed layer microwave radiometer 結氷

项目摘要

First we analyze upper-ocean/sea-ice dataset collected by several icebreakers over the whole Antarctic Ocean, along with the satellite microwave radiometer data. These analyses suggest that sea ice melts mostly on the bottom and lateral faces by the heat input (mainly solar radiation) through the open water area. Further, it is found that the negative (positive) anomalies in ice concentration in the retreat season lead to the negative (positive) anomalies in the next advance season with strong correlation, which can be regarded as ice-albedo feedback in a coupled ice-ocean system.We propose a simple ice-upper ocean coupled model in which sea ice melts only by the ocean beet supplied from the air. The model well explains the relation between ice concentration and upper-ocean in the Antarctic summer. By fitting of the model result and observation, the beat transfer coefficient between upper-ocean and sea ice can be determined. With use of this coefficient value, the model can roughly reproduce meridional retreat of sea ice.When the model is extended to two-dimensional in the meridional direction with the inclusion of the wind-drift effects, reproduction of the sea ice retreat has further progressed. This two-dimensional model can describe the following ice albedo feedback effect ; once the ice concentration is decreased by the divergent wind field, the heat input to the upper ocean is enhanced, leading to further decrease of ice concentration. This mechanism can partly explain the year-to-year variation of the sea ice retreat in the Antarctic Ocean. However, some observed results cannot be explained only by the ice-ocean coupled system, which requires the understanding of the feedback system including the atmosphere.

首先，我们分析了上层海洋/海冰数据集收集的几个破冰船在整个南极海洋，沿着卫星微波辐射计数据。这些分析表明，海冰融化主要是在底部和侧面的热量输入（主要是太阳辐射）通过开放水域。此外，还发现冰浓度在退季的负（正）距平导致下一个进季的负（正）距平，并具有很强的相关性，这在冰-海耦合系统中可以看作是冰-海耦合反馈。该模式较好地解释了南极夏季海冰密集度与上层海洋的关系。将模式结果与实测资料进行拟合，可以确定上层海洋与海冰之间的拍频传递系数。利用该系数值，模式可以大致再现海冰的纬向退缩，当模式在纬向扩展到二维并考虑风的漂移效应时，海冰退缩的再现得到了进一步的进展。该二维模式可以描述以下冰浓度的反馈效应：一旦冰浓度被辐散风场降低，向上层海洋的热量输入增加，导致冰浓度进一步降低。这一机制可以部分解释南极海冰退缩的年际变化。然而，一些观测结果不能仅用冰-海耦合系统来解释，这需要对包括大气在内的反馈系统的理解。