北冰洋太平洋扇区上层海洋热量再分配机制及其对海冰物质平衡过程的影响

The rapid decline in Arctic sea ice over the past few decades has prompted scientists to better understand the factors driving sea ice variability. Recent observation and numerical modeling revealed that, the increasing duration and area of open water during the melt season allows significant accumulation of solar energy in the upper ocean, extending below the shallow summer mixed layer. In addition, summer Pacific water provides another source of increasing warm water above the halocline entering the western Arctic from the Chukchi shelves. The excess oceanic heat that has accumulated during recent summers due to the increased solar insulation and oceanic heat convergence is a critical initial factor in preconditioning the sea ice cover before the melt season and reducing ice concentration and thickness in the western Arctic Ocean. . Analyses and syntheses of numerical model results and available observational data will be carried out in order to advance the understanding of critical processes and feedbacks affecting the oceanic forcing of sea ice in the western Arctic Ocean, where melt has been particularly pronounced. The main tasks include: Identify generation and evolution process of the near surface mesoscale eddies at the northern shelf/slope region of the Chukchi Sea and its impact on the cross-shelf transport and distribution of the warm water in the Canada Basin; Develop understanding of key physical process contributing to the significant vertical mixing of the upper ocean and the relative importance of upper ocean heat transport and air-sea heat fluxes in the sea ice variation.

北冰洋夏季融冰季节开阔水范围及持续时间的增加，显著的增强了上层海洋吸收储存太阳辐射热量的能力。此外，夏季太平洋入流水构成了混合层底部盐跃层之上暖水层的又一来源，且呈现增暖趋势。这使得太平洋扇区上层海洋热含量显著增加，进而减缓冬季海冰生长或强化夏季海冰的底部融化，尤其是在一些强物理过程，如近表层中尺度涡旋，大气气旋及上升流等所导致的垂向混合可使得这些储存在混合层底部的热量卷携至冰-海界面。. 结合观测数据及数值模拟结果，本项目将综合分析北冰洋太平洋扇区影响上层海洋热量分布及其在海冰快速变化中的关键物理过程及反馈机制。主要研究内容包括：确定楚科奇/波弗特陆坡区中尺度涡旋在上层海洋热量北向输送中的作用；量化分析太平洋扇区关键物理过程在上层海洋热量分布及海冰变化中的贡献；深入理解上层海洋热量再分配、海冰物质平衡过程及大气强迫之间的反馈机制。

全球气候变暖背景下，北冰洋上层海洋热量持续增加强化了海洋在海冰变化中的作用，但热量的分配机制与过程并不十分明确。本项目聚焦北冰洋太平洋扇区，围绕上层海洋关键过程在海洋热量再分配中的贡献这一主题，综合观测与数值模拟分析，探讨了上层海洋热量再分配机制与海冰物质平衡的关系。项目执行期间，项目组主要成员参加了中国第八次北极科学考察，开展了海冰物质平衡过程观测研究，并获取了有效数据，构建了海冰物质平衡数据集；以国际共享的冰基海洋剖面数据为主，结合已积累的历史数据系统刻画了北冰洋上层海洋混合属性的年际与季节性变化及其对上层海洋热通量分布的影响；在现有的北冰洋区域“涡分辨”耦合模式中引入潮流驱动及潮-致混合过程，探讨了潮汐与潮-致混合在北极海冰年际与季节性变化中的贡献；该技术方案已应用于全球大洋多个热点海区的区域潮汐+环流耦合系统，计划进一步实现在北极海冰业务化系统中的应用，以优化北极海冰数值预报；基于MITgcm的非静力模拟能力，探讨了二模态内孤立波在背景剪切流调制作用下的混合耗散过程，揭示了二模态内孤立波在背景剪切流作用下所具有的强耗散特征，并进一步开展了北冰洋关键地形周边潮-地相互作用的动力效应。