Regional inputs to the Massachusetts Institute of Technology global circulation model: Chukchi Sea, Arctic Ocean, 1990-1992

The observed ongoing decline of summer sea ice coverage in the Arctic Ocean results, in part, from heat carried by ocean waters. This heat enters the Arctic Ocean by direct solar heating and by the transport of heat with flows from the Atlantic Ocean and Bering Sea. The warm waters from the Atlantic Ocean are isolated from direct contact with the sea ice by subsurface colder waters. This project will develop a model that synthesizes our understanding of important physical processes in the Arctic Ocean, compare the model output to observations, use the model to increase understanding of the processes responsible for modulating heat flux to the sea ice, and understand the observed recent trends in those processes.
The principal investigator proposes to study processes that lead to water mass transformation within the Chukchi Sea, exchange across the shelfbreak to the basin interior, and the melting of ice using a very high resolution regional numerical model in conjunction with recent and historical observations. The model is a realistically configured coupled ocean/sea ice model forced by synoptic atmospheric fields and flow through Bering Strait. Physical processes responsible for exchange of mass, heat, freshwater, and tracers across the shelfbreak will be diagnosed. The circulation and fluxes in the model will be compared with in-situ mooring and hydrographic data. The objectives of the proposed study are to better understand the processes responsible for cross shelf exchange in the Pacific sector of the Arctic Ocean, their relation to ice melt in the interior, and how they might change in a changing Arctic climate. The focus of the regional model is to diagnose the mechanisms responsible for shelf-basin exchange and relate them to the basic forcing mechanisms in this region (flow through Bering Strait and the atmosphere). The efficiency of the regional model allows for large numbers of calculations to be carried out, and for hypotheses relating to exchange to be tested. Such a process-based approach allows for a general understanding of the controlling physics with broader implications for other regions and forcing scenarios.

北冰洋（Arctic Ocean）夏季海冰覆盖范围（summer sea ice coverage）持续衰减，部分诱因来自海水携带的热量。此类热量通过太阳辐射直接加热，以及大西洋（Atlantic Ocean）与白令海（Bering Sea）的洋流热输运两种途径进入北冰洋。大西洋的暖水被次表层冷水与海冰阻隔，无法与海冰直接接触。本项目将构建一套综合集成北冰洋关键物理过程（physical processes）认知的数值模式，将模式输出与观测数据（observations）进行比对，利用该模式深化对调控海冰热通量（heat flux）的物理过程的理解，并解析观测到的上述过程近期变化趋势。
本项目首席研究员拟依托超高分辨率区域数值模式（very high resolution regional numerical model），结合最新及历史观测数据，研究楚科奇海（Chukchi Sea）水团变性、陆架坡折向海盆内部的物质交换，以及海冰消融相关过程。该模式为真实配置的耦合海洋-海冰模式（coupled ocean/sea ice model），其强迫场取自天气尺度大气场（synoptic atmospheric fields）与白令海峡（Bering Strait）的洋流通量。研究将诊断跨陆架坡折的质量、热量、淡水及示踪物交换的物理机制，并将模式模拟的环流与通量与原位锚系观测（in-situ mooring）及水文数据（hydrographic data）进行比对。本研究的目标在于：深化对北冰洋太平洋扇区跨陆架交换过程的认知，阐明其与内部海冰消融的关联，以及在北极气候变化背景下的演变趋势。区域模式的核心目的是诊断陆架-海盆交换的驱动机制，并将其与本区域的基本强迫因子（白令海峡洋流与大气强迫）相联系。该区域模式的计算效率支持开展大量数值实验，以检验与物质交换相关的各类假说（hypotheses）。这种基于过程的研究方法（process-based approach）可实现对核心控制物理机制的普适性认知，对其他区域及强迫情景亦具有广泛借鉴意义。