Seasons of Change in the Arctic Environment

该奖项是根据2009年美国复苏和再投资法案(公法111-5)资助的。北极系统的季节性是其强烈的定义。太阳辐射的极端年度循环，北极与低纬度之间的相互作用，北极内部陆地、海洋和大气之间的相互作用，以及冰冻和融化的能量，这些共同赋予了北极季节性的复杂性和丰富性，这是地球上其他地方看不到的。这种季节性正在发生变化。夏季海冰面积正在减少，伴随着北冰洋秋季气温的强劲上升。西伯利亚的活跃层冻结发生在冬季的晚些时候。这些和其他正在出现的变化在未来几十年将变得更加突出，其影响有望通过系统的物理、化学、生物和社会经济组成部分进行层叠。这项研究将确定推动北极系统季节性变化的主导气候强迫、反馈和组成部分联系，它们将塑造整个21世纪的系统演变。这将需要考虑全球辐射强迫的变化，从低纬度到北极的能量和质量传输，以及北极内部陆地、海洋和大气之间的传输，以及这些变化对北极的影响？S物理、化学和生物过程。被动控制与主动控制的框架将有助于组织调查。被动控制是通过背景变暖来控制。一个例子是北极变暖将如何导致季节性积雪持续时间缩短。主动控制是指从较低纬度或北极本身内部进入北极的能量或质量输送的变化导致的季节性变化。一个例子是秋季海冰面积的减少如何导致海洋变暖，然后通过区域大气输送，可能导致邻近陆地的变暖。季节性的变化很可能经常反映出被动和主动的控制。诸如季节性异常结构的诊断将被用来通过仪器记录评估不同系统要素中的季节性如何演变。这些观测分析将指导建模实验，以检查状态变量对主动和被动控制的敏感性，以及季节性的变化将如何塑造系统的未来。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The Arctic system is strongly defined by its seasonality. The extreme annual cycle of solar radiation, interactions between the Arctic and lower latitudes, within-Arctic interactions between the land, ocean, and atmosphere, and the energetics of freeze and thaw, combine to lend a complexity and richness to Arctic seasonality not seen elsewhere on the planet. This seasonality is changing. Summer sea ice extent is declining, attended by strong autumn rises in air temperature over the Arctic Ocean. Active layer freeze-up in Siberia is occurring later in the winter. These and other emerging changes will become more prominent in coming decades, with impacts promising to cascade through the physical, chemical, biological, and socio-economic components of the system.This research will identify the dominant climate forcings, feedbacks, and component linkages driving change in Arctic system seasonality, and they will shape the evolution of the system through the 21st century. This will require consideration of changes in global radiative forcing, energy and mass transports from lower latitudes into the Arctic, and between the land, ocean, and atmosphere within the Arctic, and how these influence the Arctic?s physical, chemical, and biological processes. A framework of passive versus active controls will help to organize the investigations. A passive control is the control by background warming. An example is how Arctic warming will lead to shorter seasonal duration of snow cover. An active control refers to altered seasonality driven by changes in energy or mass transports into the Arctic from lower latitudes or within the Arctic itself. An example is how reduced autumn sea-ice extent leads to warming over the ocean, which then, through regional atmospheric transport, may lead to warming over adjacent land. Changes in seasonality will likely often reflect both passive and active controls. Diagnostics such as seasonal anomaly structures, defined as the seasonal cycle of a state variable for a given year or years relative to the long-term climatology, will be used to evaluate how seasonality in different system elements has evolved through the instrumental record. These observational analyses will guide modeling experiments to examine the sensitivity of state variables to active and passive controls and how changing seasonality will shape the future of the system.