北极海冰面积快速减退条件下冰间湖的变化及其响应研究

Arctic polynyas are significant areas for ocean-atmosphere heat exchange, high winter sea ice production with resulting brine rejection, and play a critical role in local and regional climate variability. Presently, since the retrieve of polynyas from sea ice concentration needs manual intervention and the resolution of polynyas model is very high, the study on the interannual variability and simulation of Arctic polynyas are very limited. This study will put forward a new method to automatically retrieve the variation of polynyas based on the image-processing technology. The new method overcomes the shortcoming of manual intervention in the present method. Based on the long term information of Arctic polynyas obtained through the new method, we will study the seasonal and interannual variabilities of the area of Arctic polynyas，the ocean-air heat flux and the sea ice production in the surface of Arctic polynyas. The correlation between the variations of these three variables and the significant reduction of the area of Arctic sea ice will be analyzed. The impact of the variation of polynyas on the heat budget of the atmosphere and the sea ice production in Arctic for the different time and space will be explored. At the same time, we will develop a high resolution ice-ocean coupled model to simulate the variation of polynyas in Arctic. Through the sensitivity study, we will investigate the response of the variation of polynyas to the reduction of the area of sea ice in Arctic. This study will enhance the understand to the variability of Arctic polynyas and their role in the climate variability, and have a valuable scientific meaning.

冰间湖内存在强烈的海-气相互作用和结冰析盐过程，在极区以及全球气候系统中起着重要作用。目前受无法自动提取冰间湖变化信息以及冰间湖数值模式分辨率要求高的影响，基于数据分析和数值模拟相结合的途径，研究北极冰间湖年际变化及其对海冰面积快速减少响应的研究很少。本研究拟基于数字图像处理技术，提出一种自动提取冰间湖变化信息的新方法，克服原来方法中需要人工干预的弊端。基于该方法提取北极冰间湖变化信息，研究北极冰间湖的面积、表面海-气热通量和产冰量的季节和年际变化及空间差异性，分析它们的变化同海冰面积快速减少的相关性，探讨冰间湖变化在不同时期不同区域对大气热量收支和北极海冰产量的影响。同时，构建高分辨冰-海耦合模式，实现北极冰间湖变化的数值模拟；基于该模式，通过敏感性实验，研究北极冰间湖变化对海冰面积快速减少的响应。本研究在理解冰间湖变化及其在气候变暖中的作用具有重要的科学意义。

本基金项目三年来基本完成了项目计划书的全部内容，首先，基于数值图像学中的腐蚀法和连通域方法，研究了一种自动提取高分辨率海冰密集度数据中冰间湖净水面积的算法。然后，利用该算法分析了北极冰间湖净水面积、表面净热通量、表面产冰量与产盐量的季节变化规律及其空间差异性，结果表明：北极冰间湖总净水面积在结冰初期有个极大值，随后稍微降低并维持稳定，而到了结冰末期急剧增加；总产冰量主要受净热通量影响在1月份存在极大值，总产盐量的季节变化同总产冰量的季节变化基本一致；对于不同区域，冰间湖净水面积季节变化与总净水面积基本一致；在结冰初期不同冰间湖内的产冰量和产盐量主要受净水面积的影响，增加到一定程度基本保持不变，而在结冰后期受净热通量的影响急剧减小。进一步，分析了它们的年际变化规律及其空间差异性，总体上来说冰间湖净水面积和产冰量增加，表面净热通量减小，其中靠近太平洋和大西洋入流口的冰间湖净热通量减小的速率要比其他区域快，靠近亚欧大陆的冰间湖净水面积年际增长的速率要比其他区域大。最后，基于MITgcm海洋环流模式和CICE海冰模式建立了全球高分辨率冰-海耦合数值模式，实现了对北极冰间湖的数值模拟。通过本项目的完成对北极海冰面积快速减退条件下冰间湖的变化规律及相应的物理过程有了详细深入的理解，为进一步研究北极海冰变化及其在气候变暖中的作用奠定了研究基础。