Arctic Biosphere-Atmosphere Coupling across multiple Scales (ABACUS).

气候变暖是全球碳循环被破坏的结果。北极已经在显著变暖，预计在下个世纪，高纬度地区变暖最快、最严重，达到4-7摄氏度。然而，气候、碳循环和全球能源平衡之间存在着复杂的联系，这意味着人们对这些全球变化的细节仍然知之甚少。北极还有可能加速或减缓气候变化：(I)北极土壤中大量碳储存因变暖而释放，可能会加速温室气体的积累；(Ii)树木覆盖率的增加可能会改变阳光对太空的反射，从而影响全球能源平衡；(Iii)流入北冰洋的河流流量的变化可能会影响海洋循环，从而影响西欧和北欧的气候。目前，有一些重大的未知数意味着对未来北极系统的预测仍然高度不确定。主要的不确定性涉及(I)土壤有机质(SOM)的动态，它是碳的大量储存，(Ii)北极景观的斑块，(Iii)碳在北极植被中的分配和周转，(Iv)地形、植被和土壤之间的相互作用，(V)植物生长与土壤条件之间的联系，以及(Vi)春季和秋季在控制植物和土壤活动方面的重要性。我们提出了一个主要的、相互关联的方案，包括植物和土壤研究、大气测量、飞机和卫星观测以及建模，以应对北极陆地生物圈对全球变化反应中的不确定性。总体问题是，是什么控制着北极生态系统和大气之间碳和能量交换的年际和空间变异性？我们的现场站点位于瑞典的阿比斯科(一个焦点区域在干燥冻土带，另一个在附近的树线下方)和芬兰的凯沃(一个焦点在潮湿冻土带，另一个在干燥冻土带)。在凯沃和阿比斯科，卫星图像和飞机飞行都将覆盖10公里×10公里的区域，包括这两个重点区域。该项目有八个工作包：关于植物分配和物候的WP1研究，以及主要群落类型的呼吸-生产比率(通过收获、根系测量和同位素示踪实验)。凋落物的WP2周转率、土壤有机质、土壤的景观分布(通过土壤调查、同位素标记的凋落物、确定土壤有机质年龄的炸弹C测年)。WP3小室测量土壤和植被在精细尺度上的二氧化碳和水分交换(分辨率约为1m)。WP4连续塔式测量土壤/植被和大气之间的二氧化碳和水分交换，尺度约为100米。WP5飞机在两个研究区域进行测量，记录二氧化碳和水分交换以及陆地表面的图像。这些测量范围将延伸到许多平方公里的区域。WP6通过卫星进行地球观测。我们将把来自几个卫星仪器的观测与相关实地活动中记录的植物覆盖率的测量联系起来。WP7我们使用模型来连接在不同时间和空间尺度上连接的信息。这些模型代表了我们对该系统的最好理解，我们对照来自舱、塔、飞机或卫星的独立观测来检查和改进我们的理解。我们测试我们是否能够理解来自卫星和飞机的数据，根据在舱和塔上记录的细节，以及WP1和WP2实验。我们将举办一个国际研讨会，与来自世界各地的同事分享我们的想法。我们将以野外测量为基础，通过暑期学校培养研究生，为本科生提供暑期野外体验。

Climate warming is resulting from disruption of the global carbon cycle. The Arctic is already warming significantly, and warming is expected to be fastest and greatest at high latitudes, 4-7 degreesC over the next century. However, there are complex links among climate, the carbon cycle and the global energy balance which mean that the details of such global changes remain poorly understood. The Arctic also has the potential to speed up or slow down climate change: (i) the release by warming of considerable C stores held in arctic soils may accelerate the build-up of greenhouse gases, (ii) an increase in tree-cover may alter the reflection of sunlight to space and thus affect the global energy balance, (iii) alterations in river discharge into the arctic ocean may impact on the ocean circulation and thus the climate of western and northern Europe. Currently, there are major unknowns that mean predictions of the future arctic system remain highly uncertain. The key uncertainties relate to (i) the dynamics of soil organic matter (SOM), which is a large store of C, (ii) the patchiness of the arctic landscape, (iii) the allocation and turnover of carbon in arctic vegetation, (iv) the interactions between topography, vegetation and soils, (v) the links between plant growth and soil conditions, and (vi) the importance of spring and autumn in controlling plant and soil activity. We propose a major, linked programme of plant and soil studies, atmospheric measurements, aircraft and satellite observations, and modelling, to tackle the uncertainties in the response of the arctic terrestrial biosphere to global change. The overall question is 'what controls the interannual and spatial variability of carbon and energy exchange between arctic ecosystems and the atmosphere?' Our field sites are based at Abisko, Sweden (with one focus area in dry tundra, the other just below the tree-line nearby), and Kevo, Finland (with one focus on wet tundra, the other on dry tundra). At Kevo and Abisko both satellite imagery and aircraft flights will encompass an area of 10 km x 10 km, including both focus areas. The project has eight work-packages: WP1 Studies on plant allocation and phenology, and respiration-production ratios for major community types (via harvests, root measurement and isotope tracer experiments). WP2 Turnover of litter, SOM, landscape distribution of soils (via soil surveys, isotope labelled litter, bomb C dating to determine SOM age). WP3 Chamber measurements of CO2 and water exchanges from soils and vegetation at fine scales (a resolution of ~1m). WP4 Continuous tower measurements of CO2 and water exchange between the soils/vegetation and the atmosphere at scales of ~100 m. WP5 Aircraft measurements over the two study regions, recording CO2 and water exchanges and images of the land surface. These measurements will extend over areas of many km squared. WP6 Earth Observation via satellites. We will link observations from several satellite instruments to measurements of plant cover recorded in associated field campaigns. WP7 We use models to connect the information connected at different time and space scales. The models represent our best understanding of the system, and we check and improve our understanding against independent observations, whether from chambers, towers, aircraft or satellites. We test whether we can understand the data from satellites and aircraft in terms of the detail recorded at the chambers and towers and with the WP1 and WP2 experiments. WP8 We will run an international workshop to share our ideas with colleagues from around the world. We will train post-graduates with a summer-school based around field measurement, and provide undergraduates with summer field experience.