Collaborative Research: Understanding the role of Arctic cyclones - A system approach

北极气旋是海冰变形和海洋混合的重要贡献者。风暴活动的变化以及相关的大气反馈与过去十年中高北地区季节性的加剧以及夏季海冰的消耗有关。气旋也可能对北极冰盖和海洋状态的变化做出反应，这表明大气-海洋-冰系统通过与气旋相关的过程紧密耦合。以前的北极建模研究通常使用区域模型模拟，没有大气-海洋-冰系统的完全耦合，或者完全耦合的全球气候模型不允许与观测记录进行逐年比较。这项研究将通过使用区域北极系统模型（RASM）来避免此类限制，该模型的输出直接与逐月观测记录相对应。这将允许在多个时间和空间尺度上评估冰-海洋-大气耦合过程，并将其与有限的北冰洋测量结果联系起来，以便更全面地了解气旋活动的增加如何有助于将北极表面气候转变为季节性海冰覆盖的新的、更温暖的状态，以及气旋将如何应对这种新的北冰洋状态。气旋对阿拉斯加北部和西部北极利益相关部门（包括沿海社区和海洋运输）的影响将通过与阿拉斯加气候评估和政策中心的合作进行评估，该项目的北极气旋及相关海洋和海冰状况清单将在国家冰雪数据中心存档。年度和季节性北极气旋活动的历史时间序列、北极气旋的轨迹和强度地图以及强烈或有影响力的气旋的案例研究将在项目网页上提供。该项目将聘请研究生和一名博士后，研究成果将用于项目机构的大气和海洋科学本科和研究生课程。这项工作的成果将解决美国北极地区国家战略的优先事项，并将解决理解极端事件及其在北极气候系统中的作用方面的关键不确定性。最近北极海冰的消失增加了北极海洋与大气耦合的可能性，特别是在冰浓度低或冰缘已经消退的地区。北极海洋与大气耦合增加的一个重要方面是“北极”。海洋对风暴反应的潜在增强。曾经被厚冰所缓解的地方，随着冰层变薄，风引起的冰变形和海洋混合正在增加。北冰洋冰盖的减少和相关的北冰洋变暖也可能影响气旋的强度和频率。这笔赠款将支持对北极气旋存在时大气-冰-海洋耦合变化的调查。它将增进我们对大气-海洋-冰耦合过程的理解，重点关注气旋在改变北极系统状态中的作用和响应。气旋跟踪方案将应用于重新分析，产生北极气旋位置、路径和强度的清单，这将为分析冰和上层海洋对风暴的反应提供一个框架。将记录各种强度的气旋之前、期间和之后冰浓度、海洋温度和盐度的响应以及相关的冰质量平衡。同样的分析将应用于高分辨率区域北极系统模型（RASM）的输出和一套全球气候模型（GCM）的输出。使用根据RASM的输出计算出的一组新颖的指标，将确定海洋混合的峰值时间和空间尺度、海冰变形以及与北极风暴通过相关的湍流通量，以评估气旋-海洋-海冰的耦合过程。成对的耦合 RASM 模拟之间的气旋气候学变化（仅在海冰和海洋状态方面有所不同）以及当前和 21 世纪末的 CMIP5 模拟将允许评估气旋对不断变化的海洋和冰状态的响应。该奖项由 NSF 极地计划北极部分颁发，并由 NSF GEO 项目 PREEVENTS 共同资助。

Arctic cyclones are an important contributor to sea ice deformation and oceanic mixing. Changes
in storm activity, and associated atmospheric feedbacks, have been linked to increased seasonality of the high north in the last decade, and with sea ice depletion during summer months. Cyclones are also likely to respond to changes in Arctic ice cover and ocean state indicating that
the atmosphere-ocean-ice system is tightly coupled through processes related to cyclones. Previous Arctic modeling studies typically used regional model simulations without full coupling
of the atmosphere-ocean-ice system, or fully coupled global climate models that do not permit year-on-year comparison with the observational record. This study will avoid such limitations by using
the Regional Arctic System Model (RASM), for which output corresponds directly with month-on-month observational records. This
will allow assessment of the ice-ocean-atmosphere coupling processes on multiple temporal
and spatial scales, and to relate them to limited Arctic Ocean measurements to build a more complete understanding of how increased cyclone activity may be helping to shift the surface climate of the Arctic to a new, warmer state with seasonal sea ice cover, and of how cyclones
will respond to this new Arctic Ocean state. The impact of cyclones on Arctic stakeholder sectors in northern and western Alaska, including coastal communities and marine transport, will be assessed through a partnership with the Alaska Center for Climate Assessment and Policy and the project's inventory of Arctic cyclones and associated ocean and sea ice conditions will be archived at the National Snow and Ice Data Center. Historical time series of annual and seasonal Arctic cyclone activity, maps of tracks and intensities of Arctic cyclones, and case studies of intense or impactful cyclones will be made available on a project web page. The project will engage graduate students and a post-doctoral fellow,
and results will be used in atmospheric and oceanic science undergraduate and graduate level courses at the project institutions. Outcomes from this work will be address priorities in the US National Strategy for the Arctic Region and will address key uncertainties in understanding extreme events and their role in the Arctic climate system. The recent loss of Arctic sea ice has increased the potential for ocean-atmosphere coupling
in the Arctic, especially in areas of low ice concentration or where the ice edge has receded. An important aspect of increased ocean-atmosphere Arctic coupling is the
 potential increase
of the ocean's response to storms. Where once mitigated by thick ice, wind-induced ice deformation and oceanic mixing are increasing as the ice pack thins. The decreasing Arctic ice cover and associated warming of the Arctic Ocean may also impact cyclone intensity and frequency. This grant will support investigation of changes in atmosphere-ice-ocean coupling in the presence of cyclones in the Arctic. It will advance our understanding of coupled atmosphere-ocean-ice processes with a focus on the role and response of cyclones in altering the state of the Arctic system. A cyclone tracking scheme will be applied to reanalyses, yielding an inventory of Arctic cyclone locations, tracks, and intensities that will provide a framework for analysis of ice and upper-ocean responses to storms. The responses of ice concentration, ocean temperature and salinity, and associated ice mass balance before, during, and after cyclones at a variety of intensities will be documented. The same analysis will be applied
to output from the high-resolution Regional Arctic System Model (RASM) and to output from
a suite of global climate models (GCMs). Using a novel set of metrics computed from the output of RASM, peak temporal and spatial scales of oceanic mixing, sea ice deformation, and turbulent fluxes associated with the passage of storms in the Arctic will be determined, in order to assess coupled cyclone-ocean-sea ice processes. Changes in the cyclone climatology between pairs of coupled RASM simulations, that differ only in sea ice and ocean state, and in current and end of the 21st century CMIP5 simulations will allow for assessment of cyclone response to changing ocean and ice state. This award is made by the Arctic Section of NSF Polar Programs and co-funded by the NSF GEO effort PREEVENTS.