Collaborative Research: Gas Transfer through Polar Sea Ice (GAPS) - Mechanisms of Turbulence Production in the Seasonal Ice Zone and its Control of Mixed Layer Ventilation

高纬度海洋和海冰表面的热量，动量，淡水和辐射重要的气体，如二氧化碳的通量是至关重要的了解极地，从而全球气候过程。对这些通量的实地观察以及控制它们的物理学和生物地球化学交替地受到极地海洋典型的强风和海况以及活跃条件下水、冰和空气之间复杂的潜在非线性传输路径的阻碍。冻结和部分海冰覆盖。该项目将在一个独特的受控实验室设施中研究调节海冰气体交换的物理过程的相对贡献。在一个受控的实验室环境中，将模拟在浮冰中发现的不同海冰类型的季节性演变循环，即1）煎饼冰，2）完整的冰盖，但有引线（开口），3）融化的浮冰与淡水透镜。此外，将在CRREL海冰池设施（新罕布什尔州）研究不同冻结水平下风、波浪效应、对流和冰水流剪切的不同湍流状态。 这项研究的潜在变革性质在海冰等异质和多特征环境中的海气通量交换的物理学和地球化学对于任何现有的理论或计算方法都是极具挑战性的。研究人员正在使用的观测方法，即引入化学惰性气体作为有意的示踪剂，有能力解释通过海冰进行气体交换时遇到的几个不同的限制步骤。多示踪剂（例如SF6、He、Ar、CO2.）这些调查人员在以前的实地活动中，在挑战性较小和较传统的海气边界上使用并改进了质量平衡方法。用于研究冰池实验方法的初步结果表明，通过海冰进行的气体交换与开放水域的数量不成比例，否定了原本似乎是合理的近似值。由此产生的参数化将揭示这些研究可能会建议重定向到什么是真正的速度限制步骤的海冰通量转移。这些过程对于精确的气候变化耦合地球系统模型是重要的。

AbstractHigh latitude ocean and sea ice surface fluxes of heat, momentum, fresh water and radiatively important gases such as carbon dioxide are critical to understanding polar, and thus global, climate processes. Field observations of these fluxes, and the physics and biogeochemistry that control them is hampered alternately by both the high winds and sea states typical of polar seas, and the complex potentially non-linear transport pathways between water, ice and air during conditions of active freezing and partial sea-ice cover. This project will study, in a unique controlled laboratory facility, the relative contribution of the physical processes that regulate gas exchange through sea ice.A seasonal evolution cycle of different sea-ice types found in the ice pack, namely 1) pancake ice, 2) complete ice cover, but with leads (openings), and 3) melted ice floes with a freshwater lens, will be simulated in a well controlled laboratory setting. Additionally, different turbulence regimes of wind, wave effects, convection and ice-water current shear at various levels of freezing will be studied in the CRREL sea ice pond facility (New Hampshire). Potentially transformative nature of this research The physics, and biogeochemistry of air-sea flux exchanges in heterogeneous and multi featured environment such as sea-ice is extremely challenging for any existing theory or computational approach. The observational approach that the investigators are using, introduction of chemically inert gases as deliberate tracers, has the ability to account for several different limiting steps encountered in gas exchange through sea ice. A multi-tracer (e.g. SF6, He, Ar, CO2...) mass balance approach has been used and refined by these investigators over the course of prior field campaigns at less challenging and more conventional air-sea boundaries. Preliminary results used to investigate the ice pond experimental approach have indicated that gas exchange through sea-ice does not scale with the amount of open water, negating what otherwise appeared to be a reasonable approximation. The resulting parameterization to be revealed by such studies may suggest redirection as to what really are the rate limiting steps of sea-ice flux transfers. These processes are important for accurate coupled Earth System Models of climate change.