Collaborative Research: Greening of the Arctic - Synthesis and Models to Examine the Effects of Climate, Sea-ice, and Terrain on Circumpolar Vegetation Change

摘要北极植被的变化与海冰覆盖、地表温度和一系列地形变量的变化密切相关。本研究的总体目标是：(1)通过综合一组最近可用的长期极地数据库来探索海冰/地形/植被之间的联系；(2)研究极地周围的北极植被如何响应全球气候变化；(3)将这些信息与模型相结合，帮助预测北极植被的未来响应。该项目将直接解决这样的问题：迄今为止，北极的陆地植被是如何对气候变化做出反应的，随着目前对海冰趋势的了解，北冰洋部分地区变得季节性无冰，它将如何应对未来的气候变化。根据归一化植被指数（NDVI）的测量，1981年至2001年，阿拉斯加北部的绿化面积平均增加了17%，与此同时，波弗特海的冰退缩强烈，陆地表面温度上升。NDVI的趋势与关于灌木覆盖的观测、模拟和将温度升高与生物量增加联系起来的实验证据一致。该小组将综合23年以上的地球轨道卫星数据，结合详细的极地气候、植被、地形和基底变量图，确定海洋和陆地在有记录的年份里是如何相互作用的，然后利用这些信息改进现有的北极植被变化模型。他们将主要使用NOAA卫星上的先进甚高分辨率辐射计（AVHRR）提供的地表温度、海冰和NDVI数据的时间序列。大量其他遥感数据将补充这些数据，以延长记录的长度，并观察更精细的尺度变化。研究的主要区域是由苔原植被和北极气候的存在所定义的环极地北极。北极分水岭划定的更大区域将不太详细地进行研究。他们将为这一地区建立一个环极综合地理信息系统。NDVI模式将在空间和时间上根据绘制的变量进行分析，这些变量包括陆地表面温度（LSTs）、海冰模式、地形年龄、基质、地形、海拔和区域植物群。他们将使用植被变化模型来确定迄今为止探测到的绿化是否可以用来预测北极未来的植被变化模式。利用全球植被变化模型BIOME4的空间分析将预测北极和北方植物群落格局的变化，而北极植被动态模型ArcVeg将把利用遥感探测到的变化与基于地面的植物物种组成和结构测量联系起来，以检查可以预期的变化速率。

AbstractChanges to the vegetation of the Arctic are intimately linked to changes to the sea-ice cover, land surface temperatures, and a host of terrain variables. The overarching goals of this research are to (1) explore the sea-ice/terrain/vegetation linkages by synthesizing a group of recently available long-term circumpolar databases, (2) examine how the vegetation of the circumpolar Arctic is responding to global climate change, and (3) use this information in combination with models to help predict future response of arctic vegetation. The project will address directly the question of how the terrestrial vegetation of the Arctic has responded to climate change to date and how it will respond in the future as portions of the Arctic Ocean become seasonally ice free as indicated by current understanding of trends in sea ice. An average 17% increase in greenness, as measured by the normalized difference vegetation index (NDVI), occurred in northern Alaska from 1981 to 2001, concomitant with strong ice retreat in the Beaufort Sea and rising land-surface temperatures. The trend in NDVI is consistent with observations regarding shrub cover, modeling, and experimental evidence linking temperature increases to biomass increases. The group will synthesize 23+ years of data from Earth orbiting satellites in combination with detailed circumpolar maps of climate, vegetation, terrain, and substrate variables to determine how the ocean and land have interacted during the years of record, and then use this information to improve existing models of Arctic vegetation change. They will use primarily a time series of surface temperature, sea-ice, and NDVI data from the Advanced Very High Resolution Radiometers (AVHRR) aboard the NOAA satellites. A host of other remote sensing data will complement these to extend the length of the record and to look at finer scale changes. The primary region of study is the circumpolar Arctic as defined by the presence of tundra vegetation and an Arctic climate. A larger area defined by the arctic watershed will be studied in less detail. They will create a circumpolar integrated geographic information system for this region. The NDVI patterns will be analyzed spatially and temporally with respect to mapped variables including land-surface temperatures (LSTs), sea-ice patterns, the age of the terrain, substrate, topography, elevation, and regional floras. They will use vegetation change models to determine if the greening detected thus far can be used to project future patterns of vegetation change in the Arctic. A spatial analysis using BIOME4, a global model of vegetation change, will predict changes in the patterns of arctic and boreal plant communities, and ArcVeg, a model of arctic vegetation dynamics, will link the changes detected using remote sensing to ground-based measurements of plant species composition and structure to examine the rates at which changes can be expected.