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很强的特征。太阳辐射的极端年循环，北极和低纬度地区之间的相互作用，北极内部陆地、海洋和大气之间的相互作用，以及冻结和融化的能量，这些因素结合在一起，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所看不到的。这种季节性正在改变。夏季海冰面积正在减少，北冰洋上空的气温在秋季急剧上升。西伯利亚活跃的冰层冻结将在冬季晚些时候发生。这些和其他新出现的变化将在未来几十年变得更加突出，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产生连锁反应。这项研究将确定驱动北极系统季节性变化的主要气候强迫、反馈和成分联系，它们将影响整个21世纪北极系统的演变。这将需要考虑全球辐射强迫的变化，从低纬度进入北极的能量和质量输送，以及北极内陆地、海洋和大气之间的变化，以及这些变化如何影响北极？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。被动控制是由背景变暖控制。一个例子是北极变暖如何导致季节性积雪时间缩短。主动控制是指由低纬度地区或北极内部进入北极的能量或物质运输的变化所驱动的季节性变化。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，可能导致邻近陆地变暖。季节性的变化可能经常反映被动和主动控制。诊断方法，如季节性异常结构，被定义为相对于长期气候学在给定年份或年份的状态变量的季节周期，将用于评估不同系统要素的季节性如何通过仪器记录演变。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.