快速变化期北极中层水的通风过程及其主要影响研究

The Arctic Ocean is one of the sensitive regions in global climate system. The changes in the Arctic Ocean play important role in global and China's climate. The rapid sea ice decline in the Arctic Ocean has occurred since 1990s. Warming of the Arctic Intermediate Water (AIW) was one of the factors for sea ice decline. However, the mechanism and impacts of AIW on sea ice is still unknown. In the project, we propose the study on processes of ventilation of AIW, and evaluate its impacts on sea ice in the Arctic Ocean. The ventilation of AIW will be recovered from historical observation data and diagnosed with the one-dimension (1-D) and two-dimension (2-D) ice-ocean coupled model. Different parameterization schemes of vertical mixing for ventilation of AIW will be tested and verified with observation data in 1-D and 2-D model experiments. The ventilation processes of AIW and impacts on sea ice will be simulated and evaluated with the three-dimension（3-D）Arctic ice-ocean coupled model with the specified vertical mixing schemes tested in 1-D and 2-D experiments driven by realistic forcing. The study will provide the scientific evidences for making improved predictions of future Arctic Ocean.

北冰洋是全球气候变化最敏感的区域之一，它的变化对于全球和我国气候有非常深远的影响。自上世纪90年代以来，北冰洋已经进入一个以海冰快速减少为特征的快速变化期，海冰减少与北极中层水变暖密切相关。但是，北极中层水如何影响海冰减少的机制尚不清楚。本项目将针对这一问题开展研究，通过收集国内外北冰洋现场观测资料，分析北极中层水的通风、垂向混合与热量传输的基本特征；利用海洋－海冰的耦合模型，通过一维、二维模型试验，和北冰洋真实强迫条件的三维数值模拟计算，诊断并找出北极中层水发生通风的条件和影响因素；探讨中层水通风发生的物理机制；评估中层水通风对北冰洋水体结构和海冰的影响，为北冰洋未来变化的预测提供科学依据。

北极中层水是北极热含量最大的水体，热量的释放对北极的海洋上层结构和海冰有重要影响。通过对加拿大海盆的2003-2013年间长期锚系系统观测和大面观测温盐剖面资料的分析，对应的北极历史海冰最小年份的2007年, 北极中层水这前后的变化最为显著，表现为核心温度显著降低，深度范围变浅，中层水热量大量释放为特征。建立北极高分率海洋-海冰模型，对比验证了不同分辨率对于北极环流、北极陆架陆坡动力学及通过关键海峡通道与外界交换的影响，提出了模拟包括北极中层水等北极变化的分辨率要求。基于该模型系统成功反演了过去三十多年的高分辨率的北极海洋-海冰后报场，通过与多源现场观测海冰密集度和厚度数据的对比，模型结果不仅很好地刻画了海冰的变化趋势，而且海冰厚度的模拟结果也表现出非常好的可比性，这是其他海洋模型仍然存在的一个困难，该模型系统的结果体现出了北极中层水的演变，包括通风过程，北极海冰变化对海洋的影响。