GLOBAL GLACIOLOGY
Here you will find four glaciological datasets at the global scale, on which the world's glacier ice interacts with the rest of the cryosphere and the hydrosphere to pose a number of problems for modern society.

Foremost among these problems is the water balance of the ocean. After the ocean, glaciers form the second largest reservoir of water on Earth, and exchanges of mass between the two imply changes in sea level - with potentially enormous socioeconomic consequences.

Nearly all of the frozen water is in the two ice sheets on Antarctica and Greenland, but these bodies require millennia to respond dynamically to the climatic forcing which brings about exchanges between the cryosphere and the ocean. (Recent evidence, however, suggests that they can respond unnervingly rapidly to changes in indirect climatic forcing via the oceans.) Outside the ice sheets glacier ice is extremely restricted, covering about 0.7 Mm2 of the Earth's surface (511.0 Mm2), yet these other glaciers are all much more quick to respond, doing so on timescales of decades to centuries. This makes it vital to understand their state of health, quantified as the "mass balance". Glacier mass balance, however, is in phase with changes in the climate, so that the slow dynamic response of the largest glaciers is less relevant than one might think to social problems such as global warming.

GGHYDRO field GLAC - Percentage extent of glacier ice
Percentage extent of glacier ice (GGHYDRO field GLAC)

GMBAL
Pentadal average global mass balance of small glaciers
Left: red squares - pentadal averages of direct measurements; blue circles - pentadal averages of geodetic measurements. Right: red squares - spatially-corrected global averages of direct measurements; dark blue triangles, with grey confidence region - similar averages of both direct and geodetic measurements.
Mass balance measurements are expensive and difficult undertakings on objects which are mostly remote and inaccessible. The measurements are therefore few, and with present technology they are also inaccurate. This, however, makes them, and the information they contain, more rather than less important in the socioeconomic context. We have assembled a collection of published measurements of the annual mass balance of small glaciers which is as complete as possible. Click for more information on this collection, which is organized as the dataset GMBAL.

The graph summarizes the contents of GMBAL. The vertical scale is in sea-level equivalents: the negative of global average glacier mass balance, spread over the ocean surface and expressed as an equivalent depth. Geodetic measurements offer much better spatial coverage as well as the obvious improvement in historical reach. The close-up of recent decades (right), in which we have enough measurements to correct for their uneven geographical distribution, shows the importance of spatial correction: for example the corrected average for 2000-2005 is only 1.1 mm a-1 SLE (including geodetic measurements) as against the ∼1.7 mm a-1 SLE of the uncorrected average in the left panel. (Note that in general the most recent pentad is incomplete in these graphs.)


GMBANAL
The measurements in GMBAL, which are sparse and unevenly distributed, require further processing to yield estimates at regional and global scales. As well as simple unweighted arithmetic averages of the measurements, GMBANAL provides spatially-corrected estimates, obtained by interpolation of all measurements (direct only, and also both direct and geodetic) to all glacierized cells of a 1° grid. The grid is derived from the 0.5° grid of the Randolph Glacier Inventory (Pfeffer et al. 2014; Arendt et al. 2015). The estimates are pentadal averages; averages of serially-uncorrelated annual samples (such as those of glacier mass balance) over five-year periods are less uncertain than annual averages by a factor of about 45%, and the reduced temporal resolution also mitigates somewhat the low temporal resolution of most of the geodetic measurements. Click for more information on this dataset.

GMBANAL - Analysis of global glacier mass balance
Blue envelope: Arithmetic averages of annual measurements by the direct method; Red line: Pentadal global-average mass balance, estimated by spatial interpolation of both direct and geodetic measurements to all glacierized cells of a 1° grid


World Glacier Inventory - Extended Format (WGI-XF)
Distribution of dates in the Randolph inventory
Distribution of dates in version 5.0 (yellow bars) and version 4.0 (red lines) of the Randolph Glacier Inventory.
The World Glacier Inventory is an idea conceived in 1955, when it was decided that a complete global list of the world's glaciers should be prepared by the end of the International Geophysical Year in 1958. Fifty years on, it is clear that the time needed for the job was wildly underestimated, but recently the job was indeed completed in the form of the Randolph Glacier Inventory . A project at Trent University was one of the precursors of the Randolph Glacier Inventory, aiming to revitalize the World Glacier Inventory by rescuing as much as possible of the many regional achievements to date, adding to the total number of inventoried glaciers, and presenting the ensemble of information in a unified, modern format. The outcome of this project, remains available and contains some information about glaciers that is not accessible elsewhere.



GGHYDRO
The study of climate and of climatic change requires accurate knowledge of how the fluid in the atmosphere exchanges mass, energy and momentum with its bed: the land and water at the Earth's surface. Our dataset GGHYDRO is a contribution to this knowledge, with the hydrography of the land surface as its focus. It contains, among other things, a digital map of the cryosphere showing the global distribution of permafrost, glacier ice and sea ice. Click for more information on this dataset.

GGHYDRO field BAS2 - Smaller drainage basins
BAS2 - the Earth's land surface subdivided into about 150 drainage basins: an example of the non-glaciological content of GGHYDRO.


References
Arendt, A.A., T. Bolch, J.G. Cogley, A. Gardner, J.O. Hagen, R. Hock, G. Kaser, W.T. Pfeffer, G. Moholdt, F. Paul, V. Radić, L. Andreassen, S. Bajracharya, M. Beedle, E. Berthier, R. Bhambri, A. Bliss, I. Brown, E. Burgess, D. Burgess, F. Cawkwell, T. Chinn, L. Copland, B. Davies, H. de Angelis, E. Dolgova, K. Filbert, R. Forester, A. Fountain, H. Frey, B. Giffen, N. Glasser, S. Gurney, W. Hagg, D. Hall, U.K. Haritashya, G. Hartmann, C. Helm, S. Herreid, I. Howat, G. Kapustin, T. Khromova, C. Kienholz, M. König, J. Kohler, D. Kriegel, S. Kutuzov, I. Lavrentiev, R. Le Bris, J. Lund, W. Manley, C. Mayer, E. Miles, X. Li, B. Menounos, A. Mercer, N. Mölg, P. Mool, G. Nosenko, A. Negrete, C. Nuth, R. Pettersson, A. Racoviteanu, R. Ranzi, P. Rastner, F. Rau, J. Rich, H. Rott, C. Schneider, Y. Seliverstov, M. Sharp, O. Sigurðsson, C. Stokes, R. Wheate, S. Winsvold, G. Wolken, F. Wyatt and N. Zheltyhina, 2015, Randolph Glacier Inventory - A Dataset of Global Glacier Outlines: Version 5.0. GLIMS Technical Report, National Snow and Ice Data Center, Boulder, USA. Digital Media.

Pfeffer, W.T., A.A. Arendt, A. Bliss, T. Bolch, J.G. Cogley, A.S. Gardner, J.O. Hagen, R. Hock, G. Kaser, C. Kienholz, E.S. Miles, G. Moholdt, N. Mölg, F. Paul, V. Radić, P. Rastner, B.H. Raup, J. Rich, M.J. Sharp and the Randolph Consortium, 2014, The Randolph Glacier Inventory: a globally complete inventory of glaciers, Journal of Glaciology, 60(221), 522-537. doi: 10.3189/2014JoG13J176.