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SPRI Review 1996: Research Overviews

Research Overviews

Remote Sensing Group

Dr W.G. Rees

M. Williams, A.W. Bingham, D.L. Feltham, G.J. Ager

The Remote Sensing Group continued its work of developing methods for the analysis of satellite data and applying them to the study of polar environments. As in the previous few years, this research embraced land ice, sea ice and icebergs, and tundra areas.

The international Ice Pilot Application Project (IPAP) came to an end during the year, having successfully demonstrated the potential of satellite radar data to produce, almost in real time, operationally useful data regarding the distribution, concentration, and motion of icebergs and sea ice. A paper (Willis and others 1996) was published describing the performance of this system in detecting icebergs and showing that bergs as small as 15 m can be detected under ideal conditions, and that bergs 100 m across can almost always be detected. This work was developed beyond the end of the IPAP project during a visit by Dr Ray Williams from the University of Tasmania. Dr Williams and Dr Gareth Rees collaborated on the development of a more sophisticated iceberg-detection algorithm and applied it to radar images of coastal areas in the Antarctic. The technique will form part of a system being developed by the Australian Cooperative Research Centre for the Antarctic and Southern Ocean Environment for monitoring the mass balance of the Antarctic ice sheet.

Daniel Feltham (Research Student) continued his research, sponsored by the UK Meteorological Office, in collaboration with Dr Grae Worster of the Department of Applied Mathematics and Theoretical Physics at Cambridge. This research involves the mathematical modelling of the drainage of brine from sea ice. During the year, various linear treatments of brine drainage were formulated, and attention was then turned to the growth of sea ice when there is relative motion between the ice and the ocean. A complete linear stability analysis was conducted. This project will lead to an improved understanding of the thermodynamic processes involved in the growth of sea ice, and ultimately to better models of the ice-ocean-atmosphere interactions, uncertainty about which is currently hampering the development of reliable global climate models.

The Remote Sensing Group's expertise in remote sensing of sea ice, especially using microwave methods, was recognised by the appointment of Dr Rees by the British National Space Centre (BNSC) as the technical assessor for a project to develop a Sea Ice Information Service. This project is sponsored by BNSC and led by Earth Observation Sciences Ltd.

During the year the Remote Sensing Group also made progress towards its goal of being able to monitor climatological effects on glaciers and ice sheets using spaceborne data. Andrew Bingham (Research Student) continued his research into the synergies between different satellite data sets. Field data collected from Finsterwalderbreen, Svalbard, in summer 1995 were analysed in conjunction with spaceborne synthetic aperture radar (SAR) images to refine the current understanding of how surface features are revealed in the SAR images. New techniques were developed to correct SAR images for the effects of topographic relief using a Digital Elevation Model, and to couple this with Landsat optical imagery to determine the position of a glacier's equilibrium line at the end of the ablation season. This approach will be important for validating the energy-balance models of the response of Arctic glaciers to possible climate warming. Techniques were also developed for determining glacier surface temperatures from a combination of AVHRR and ATSR thermal infrared data. Bingham also attended the NASA Earth Science Summer School at the California Institute of Technology in Pasadena.

Gisela Ager investigated the use of the shape-from shading method, originally developed by Dr Rees for determining the topography of ice caps using Landsat optical data, for small mountain glaciers.

Work also proceeded on the Remote Sensing Group's third main area, the investigation of high-latitude vegetation subjected to technogenic stress. The Kola Peninsula project, performed in collaboration with the Geography Faculty of Moscow State University and funded by the UK Department of the Environment, came to an end during the year, resulting in the issuing of a comprehensive final report and the preparation of several articles for publication in English and Russian. The success of this project in showing that satellite images can be analysed to show not only gross damage to tundra vegetation as a result of atmospheric pollution, but also the early effects of ecological stress, encouraged the Moscow-Cambridge team to attempt to continue extending the work to the more heavily polluted areas round Norilsk in Siberia. Unfortunately a combination of financial and political uncertainties forced the postponement of a field trip to Siberia planned summer 1996. It is now planned that this will take place in 1997. Meredith Williams (Research Assistant) left the Institute, on completion of his contract, to take up a PhD studentship at Aberystwyth.

The related area of research, into the effects of oil contamination on frozen ground and the extent to which these can be monitored and modelled from spaceborne observations, continued to develop throughout the year. This research is currently being carried out as a collaboration between Dr Rees and Professor Peter Williams of Carleton University, but negotiations to include both Moscow State University and the University of Caen took place during the year. In April 1996 Dr Rees visited the Geotechnical Science Laboratories of Carleton University, and Professor Williams and Dr Rees visited the US Army Cold Regions Research and Engineering Laboratories at Hanover, New Hampshire, where their research proposals attracted considerable interest. In June 1996, Professor Williams and Dr Rees visited the University of Caen and the Centre National des Recherches Scientifiques' Station de Gel, also at Caen. These visits were supported by the US Army's European Research Office and the British Council, respectively.

During the year Dr Rees was appointed as a member of the NERC Earth Observation Science and Technology Board's working group on future Earth Observation requirements. He was also elected a Fellow of the Institute of Physics. In October, Dr Rees and M. Williams attended a conference on Mapping and monitoring of ecosystem disturbance using remote sensing at Leicester University. In March 1996, Dr Rees gave a talk on the use of satellites for studying glaciers to an audience of about 350 as part of National Science Week in Cambridge. That same month, he presented the results of the Kola Peninsula project to the Sheffield Centre for Earth Observation Science.