Collaborative Research: Seasonality of circumpolar tundra - ocean and atmosphere controls and effects on energy and carbon budgets

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。过去几十年来北极夏季植被生产的规模和季节性变化已被记录在案。这些变化可能会加速，并对整个北极陆地系统产生影响，特别是能源和元素的收支，并将反馈到海洋和大气系统。该项目将描述陆地表面绿度与一系列陆地、大气和海洋特征之间的季节性联系，重点是白令海/博福特海，在过去25年中，那里的归一化植被指数有很强的正增长，以及欧亚大陆北极中西部地区，那里的归一化植被指数趋势略有下降。将讨论以下问题：（1）北极系统各组成部分（海冰密集度和厚度、海洋和陆地表面温度、海洋热通量、积雪和归一化差异植被指数规定的植被）的季节性在空间和时间上有哪些变化？具体地说，这些在环极北极的纬向和纬向变化是如何发生的？(2)大气和海洋环流模式在控制陆地温度和植被生长的季节性方面起什么作用？(3)这些北极系统组成部分的季节性变化如何影响植被生长和碳固存？ 该项目将利用卫星和现场数据集，记录整个北极区域尺度上冻原和海洋气候系统的季节性（每日至每月的时间尺度）。再分析数据集将被用来描述当地的环流特征。将使用一个泛北极冰-海洋模式来描述与冻原植被有关的海洋环流模式，并应用统计分析来调查海洋-大气-陆地关系的机制。植被变化模型（ArcVeg）将分析土地温度变化对碳生产的影响，沿着气候，扰动和土壤梯度。该模型将在季节性研究中得到增强，包括过渡到每日时间步长，并将允许检查季节性变化对不同功能植物类型和不同植物组织类型积累的碳的影响。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Changes in the magnitude and seasonality of Arctic summer vegetation production over the past several decades have been documented. These changes will likely accelerate and have consequences for the entire Arctic terrestrial system, in particular energy and element budgets, and will also feed back to marine and atmospheric systems. This project will characterize the seasonal linkages between the land surface greenness and a suite of land, atmosphere, and ocean characteristics, focusing on the Beringia/Beaufort Sea, where there have been strong positive increases in the Normalized Difference Vegetation Index (NDVI) over the past 25 years, and the west-central Arctic Eurasia region , where the NDVI trends have been slightly negative. The following questions will be addressed: (1) What are the spatial and temporal variabilities in the seasonality of various arctic system components (sea-ice concentration and thickness, ocean and land surface temperatures, ocean heat fluxes, snow cover, and vegetation as specified by the NDVI? Specifically, how do these vary zonally and meridionally in the circumpolar Arctic? (2) What role do the atmosphere and ocean circulation patterns play in controlling the seasonality of land temperatures and vegetation production? (3) How do changes in the seasonality of these arctic system components affect vegetation growth and carbon sequestration? Using both satellite and in situ data sets, this project will document the seasonal (daily to monthly timescales) of the tundra and marine climate systems at a regional scale throughout the Arctic. Reanalysis data sets will be employed to describe local circulation characteristics. A pan-arctic ice-ocean model will be used to describe ocean circulation patterns relevant for tundra vegetation, with the application of statistical analyses to investigate mechanisms of ocean-atmosphere-land relationships. A vegetation change model (ArcVeg) will analyze the consequences of land temperature changes for carbon production along climate, disturbance, and soil gradients. This model will be enhanced for seasonality studies, including transition to a daily time step, and will allow the examination of effects of seasonality changes on the carbon accumulated by different functional plant types and into different plant tissue types.