Why do we care about glaciers?
Glacier changes are recognized as one of the best natural indicators of climate change as glaciers only respond to more long-term climatic trends. The analysis of their changes through time is thus providing insights into past climatic fluctuations as well as on the impacts of current climate change. Glaciers are a major contributor to global sea-level rise and a precious resource of fresh water in many arid regions around the world (for human consumption and agriculture), a source of natural hazards, an important factor for hydro-power production and run-off, as well as for recreation and tourism. The monitoring of glacier changes is thus an important component of the global climate observing system (GCOS) and vital for many aspects of human life.
The field-based monitoring of selected glaciers started in 1894 with the regular observation of glacier length changes (or terminus fluctuations) and provides one of the longest climate data records we have. Since a few decades, satellite data provide globally more complete and complimentary information on glacier changes through time. In particular, changes in glacier extent and volume are mostly determined from satellite data these days, but also surface flow velocities are regularly derived for many of the 215,000 glaciers globally. These three variables (glacier extent, elevation change and velocities) are also investigated by the Glaciers CCI project.
An important dataset to spatially constrain calculations and determine glacier-specific changes is a globally complete glacier inventory, that provides outlines of each glacier in a vector format (shape file), supplemented by attribute information providing glacier characteristics. Such a dataset (the Randolph Glacier Inventory) was created by a major community effort in 2012 to improve global-scale calculations for IPCC AR5 and has been updated and improved several times since. The Glaciers CCI project and its pre-cursor GlobGlacier contributed substantially to this effort by providing glacier inventories for key regions.
A study (=> link) by Glaciers CCI team members analysed elevation changes across glaciers in High Mountain Asia (HMA) and revealed for the first time the high spatial variability of glacier response to climate change in this region. Subsequent studies revealed a very dense picture of very unusual glacier changes in the region. Our elevation change observations in HMA were complemented by local-scale to region-wide flow velocity maps, of which the latter are also derived in several other regions of the world for several points in time (e.g. Arctic Islands) using historic EO data. A related study revealed that flow velocities of numerous glaciers have significantly increased over the past decades, despite pre-dominantly negative mass balances.
Of particular interest these days are so-called surge-type glaciers that suddenly start to transport large amounts of mass from a higher reservoir zone towards the terminus, sometimes advancing over several kilometres in a few months or years. The erratic behaviour of these glaciers is still poorly understood, largely decoupled from climate forcing, related to natural hazards (outbursts of lakes that follow blocking of rivers) and contributing large amounts of ice mass to the ocean that are not yet properly accounted for in models determining future sea-level rise. There is thus some need to further strengthen research on this special type of glaciers, which is the main focus of the current Glaciers CCI+ project.