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

Lead Research Organisation: University College London
Department Name: Geography


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 degrees C 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. We propose a major, linked programme of plant and soil studies, atmospheric measurements, aircraft and satellite observations, and modelling, to improve our understanding of the response of the arctic terrestrial biosphere to climate change. Our overall aim is to determine what controls the temporal and spatial variability of carbon, water 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 in birch forest), 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, soil organic matter (SOM), landscape distribution of soils (via soil surveys, isotope labelled litter, bomb C dating to determine SOM age), CH4 emissions. WP3 Chamber measurements of C 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, and records of snow depth, soil moisture and climate. WP5 Aircraft measurements over the two study regions, recording CO2 and water exchanges and images of the land surface and profiles of CH4. 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 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.
Description Objective: To generate improved estimates of the total C stocks of arctic vegetation
We have developed new, highly detailed 3D models of Fennoscandian mountain birch, from detailed field measurements; the first time this has been done for broadleaf deciduous canopies. We have used the models to predict the information content of new EO measurements, particularly airborne and space-borne lidar, and quantify measurement uncertainties. We have used the models to estimate birch biomass across the landscape from combined lidar and reflectance measurements. We have shown that birch canopies at two contrasting locations are structurally indistinguishable, but with somewhat different phenology, possibly related to the local topography and persistence of snow cover. We have shown that satellite data can be used to identify changes in deciduous vegetation cover due in Fennoscandia due to insect outbreaks linked to climate variations, with consequences for C stocks. We have generated improved maps of deciduous forest, tundra and mire from test sites and quantified the effects of scale on these estimates.
We have developed elevation maps using lidar observations and high resolution multi-angle satellite data. These are the basis for improved vegetation cover maps at multiple scales from 1-500m. As the scale of observation is reduced from 5-500m, it is possible to consistently identify deciduous birch forest and mire using multispectral EO data, even in highly heterogeneous Fennoscandian landscapes, while areas of tundra become harder to identify, particular when interspersed with deciduous forest.
Outcome: 3D models of deciduous vegetation to improve analysis of satellite data in tundra.
Exploitation Route To advance the interpretation of remote sensing data
Sectors Environment

Description To support knowledge exchange activities with the public, including science festival presentations on arctic climate change
First Year Of Impact 2007
Sector Education
Impact Types Societal