GlobGlacier: A NEW ESA PROJECT TO MAP THE WORLD’S GLACIERS AND ICE CAPS FROM SPACE

In this paper we provide an overview of the GlobGlacier project, a new data user element activity within ESA’s Living Planet program. The main aim of the project is to map glaciers from key regions all over the world and to generate digital glacier outlines in large quantities in order to fill data gaps in currently existing databases (GLIMS and World Glacier Inventory, WGI). Further goals are to provide additional information (snow line, topography, elevation change, velocity) for a smaller number of glaciers in selected regions from space-borne sensors and to document the applied techniques for later use. Apart from a short description of the project and the products that are generated, an overview of available remote sensing techniques that have been used on glaciers and ice caps is given. BACKGROUND Glacier changes are key indicators of climatic changes as they show an enhanced and well recognisable reaction to even small climatic fluctuations, which results from their proximity to melting conditions (1). They have thus been selected together with ice caps as one of the essential climate variables (ECVs) in the implementation plan of the global climate observing system (2). Their monitoring is organised in a tiered strategy within the global terrestrial network for glaciers (GTN-G) which is operated by the world glacier monitoring service (WGMS). Within GTN-G, annual measurements of mass balance (about 50 glaciers at Tier levels 2 and 3) and length changes (about 550 glaciers at Tier 4) are performed (3). Detailed glacier inventory data (Tier 5) from the 1960s to 1970s exist as point information in the world glacier inventory (WGI) for c. 71,000 glaciers, which is about 40% of the estimated 160,000 glaciers worldwide. Thus, (a) the current sample of glaciers with annual measurements is very small and not necessarily representative for the changes at a global scale, and (b) the WGI is not complete and difficult to use for change assessment as, in general, the glacier perimeter related to the sampled point data is not known. According to (4), melting glaciers and ice caps might provide an even larger contribution to the global sea level rise in the coming decades than the two continental ice sheets Greenland and Antarctica. Hence, there is an urgent necessity to generate more complete and representative data sets for global assessments (e.g., 5,6). The GCOS report ’Systematic observation requirements for satellite based products for climate change’ (7) and the IGOS cryosphere theme report (8) have confirmed the important contribution of satellite observations to monitor glacier and ice caps around the world. In this respect, the Global Land Ice Measurements from Space (GLIMS) initiative has started to compile glacier outlines in a digital vector format from satellite data and other sources in a publicly accessible database (9). In 2007, the European Space Agency (ESA) has initiated a new activity within its data user element (DUE) programme that augments ongoing activities: the GlobGlacier project. Its major aim is to establish services for glacier monitoring from space, building upon, complementing and strengthening the EARSeL eProceedings 8, 1/2009 12 existing network and services (GLIMS, WGMS) of global glacier monitoring (10). According to ESA standards, the set-up of the data processing will be worked out in phase 1 (16 months) and the application and data generation will mostly take place during phase 2 (20 months). The project started in Nov 2007 for a period of three years, is led by the University of Zurich, has four partners (Table 1) and ten user group members (Table 2) which will be actively involved in the project (e.g. for product evaluation) and represent different interest groups. The project will map glaciers from key regions all over the world, generate digital outlines in large quantities, and obtain additional information for a smaller number of representative regions. The selection criteria for the key regions are given by the Statement of Work from ESA and the requirements of the user group. Among others, the criteria were: to fill the gaps in the WGI and the GLIMS database, select regions with a potential strong contribution to sea level rise or as a (regional) water resource, include sites with glacier related hazards, and compile glacier data from all continents. Table 1: The consortium of GlobGlacier. Name Affiliation (Abbreviation) Country Products F. Paul Dept. of Geography, University of Zurich (GIUZ) CH Outlines, terminus A. Kääb Dept. of Geoscieneces, University of Oslo (GUIO) NO Topography H. Rott Environmental Earth Observation, Innsbruck (ENVEO) AU Snow lines A. Shepherd School of Geosciences, University of Edinburgh (SGUE) UK Elevation change T. Strozzi Gamma Remote Sensing, Gümligen (Gamma) CH Velocity fields Table 2: The members of the GlobGlacier user group, their affiliation, role and region of expertise (m.: modelling). Name Institute Role Region Name Institute Role Region M. Zemp UZH WGMS global L. Andreassen NVE Hydrologic m. Norway B. Raup NSIDC GLIMS global S. Kotlarski MPI Climate m. global M. Citterio GEUS Arctic Greenland R. Braithwaite IMAU Sea level rise global R. Wheate UNBC WC2N Canada H. Oerlemans SED Cryospheric m. global P. Mool ICIMOD Hazard Himalaya T. Khromova RAS CliC Russia GLOBGLACIER WORKFLOW AND PRODUCTS Workflow The organisation and workflow of the project is illustrated in Figure 1. The upper part of the diagram illustrates the consolidation of the user requirements (in close cooperation with the user group) and the selection of key regions (based on the above criteria and the available satellite data). The middle part shows the individual work packages (which are related to the requested products), the responsible consortium members, and the relation between the data products. Glacier outlines from work package 1 (WP1) will be provided to all other WPs for consistent product creation. A subset of the satellite scenes selected for WP1 will also be used to perform the snow classification in WP2. In principle, two different types of products (deliverables) will be generated by GlobGlacier: Text documents and a certain quantity of data products (Table 3). While the former will summarise the methodological and technical aspects of the project, the latter will make a major contribution to existing databases (GLIMS, WGMS). A major aim of GlobGlacier is to aid in completing the WGI and supplementing the existing point information (1D) in the WGI with digital vector outlines (2D) of glaciers and ice caps. This requires a close coordination with currently ongoing activities, in particular with the GLIMS initiative. Further goals of GlobGlacier are an extension of the currently observed glacier fluctuations (mass and length changes) from direct satellite measurements (products terminus and elevation change), as well as indirect means that could be useful to estimate glacier mass balance (snow lines, velocity fields). As the products should satisfy very different demands from the members of the user group, EARSeL eProceedings 8, 1/2009 13 the main product glacier outlines have been subdivided into three levels of detail (L0 to L2). The topographic information (i.e., a digital elevation model, DEM) as provided by workpackage 3 (WP3) is required to derive most of the other products (e.g. topographic glacier inventory data or altitude of the snowline). In Table 3 a short overview of the created data products is given. Figure 1: Organigram of GlobGlacier as developed for the proposal. WP is work package, URD is user requirements document. After the first user group meeting it has been decided that the end product of WP2 will be the late summer snow line (LSSL) rather than ELA. Table 3: Proposed product quantities for the total project duration and in phase 1 / 2 Outline Terminus Snow line Topography Elevation ch. Velocity WP 1 1 2 3 4 5 Phase 1 200