The Alaska-Yukon glaciers cover about 100,000 km² in Alaska and adjacent parts of Canada. This is equal to the ice covered area of the Queen Elizabeth Islands of Arctic Canada; either of which is the third largest ice mass on earth after Antarctica (13.6 x10⁶ km²) and Greenland (1.7x10⁶ km²). The Alaska-Yukon glaciers differ from the other large glacier covered areas because of their high rates of mass flux, large amounts of temperate ice, and their location in areas of vigorous and expanding human activity. The glaciers of Alaska feed every major river in the state except the Colville and play an important role in the oceanography of the North Pacific Ocean and in the climate of North America. Glacier runoff constitutes a line-source of fresh water along the south gulf coast of Alaska that produces a fresh-water stream equal in discharge to the Mississippi River. When seeking the tie between climate and these glaciers it is important to understand that some glacier changes are driven by mechanisms that are only indirectly linked to climate, or are completely independent of climate; these include: the calving-glacier cycle, surging, and glacier-volcano interactions. Furthermore, the gradient of climates from Maritime to continental, to Arctic polar basin across Alaska is the strongest of any on earth. Glaciers exist in each climate region and should be studied as a continuum from maritime to Arctic-desert types.

The glacier data base for Alaska includes glacial geologic reconstructions of Late Cenozoic glacier extents; 18^th century terminus positions recorded by La Perouse, Cook, Vancouver, and others; and detailed studies of glaciers near the close of the 19^th century by Reid, Gilbert, Tarr, and Martin (see T.D. Hamilton, 1994, for summary and references). Compilations of statewide glacier data have been published by Capps (1932), Pewe and others (1953), Karlstrom and others (1964), Coulter and others (1965), Pewe (1975), and Mayo (1984) (see T.D. Hamilton, 1994 for full references), and in Snyder (1996). The database also includes a large archive of aerial photographs and satellite images located at the GeoData Center of the University of Alaska's Geophysical Institute at Fairbanks, Alaska (see attached table, p. 35).

Seventy three glaciers in Alaska have baseline mass balance or detailed topology data that are important ground truth for the analysis and interpretation of satellite data (see attached table, p. 31, which includes glaciers in Canada and the Western United States). An additional number of glaciers have long series of terminus change measurements or have begun observations that are intended to produce long-term series (note especially those in Denali National Park and Preserve). In return, the surface-based data collection programs expect to benefit from new understanding of the relation between the measurement sites and regional glacier activity and guidance and backing in targeting effective expansion of the surface-based data collection efforts. The listed baseline glaciers are not uniformly distributed geographically but do include representatives for each of the recognized climate regions of Alaska. These data are products of several programmatic efforts: 1) Eight large-scale glacier maps produced by the International Geophysical Year (IGY) program in Alaska during the late 1950's. Many of the IGY glacier studies included some mass balance measurements; 2) Three International Hydrologic Decade (IHD) glacier mass balance programs operated during the 1960's (see accompanying table); 3) The U.S. Geological Survey benchmark glaciers (Gulkana and Wolverine), which have been sustained since beginning as IHD sites, include mass balance, climatological, and ice kinematics data; 4) Mass balance and longitudinal profiling of selected glaciers in Denali National Park and Preserve (DNP&P), Alaska, begun during 1991; a long-term commitment to continued surface-based measurements will be augmented by remote sensing information. The objective of the DNP&P work is regional characterization of glacier mass balance; 5) Airborne laser altitude profiles of 65 glaciers begun during 1992 under National Science Foundation funding to Echelmeyer and Harrison (written communication, 1996); 6) The long-term studies by the Geologic division of the Bering, Malaspina, and Mendenhall Galciers; 7) The late Williams O. Field's work on North American glaciers, especially his research on glaciers in Glacier Bay National Monument, AK, that he began in the 1920's; and 8) The recently completed contribution to the Glaciers of North America volume of the Satellite Image Atlas of Glaciers of the World by Bruce F. Molnia (GD) and Robert M. Krimmel (WRD) (in press) on the Glaciers of Alaska.

An important subset of the listed glaciers are those with the longest records and where surface-based and remote sensing monitoring programs continue to operate. The Gulkana and Wolverine Glaciers, the U.S. Geological Survey benchmark glaciers in Alaska, have the longest continuous time series of mass balance, and climatological measurements in Alaska. These records begin in the mid-1960's and are augmented by ice kinematics measurements that began during the early 1970's and, for some years, basin runoff was measured. Gulkana and Wolverine Glaciers have also been profiled by Echelmeyer and Harrison and are designated National Technical Means (NTM) fiducial sites. The next longest mass-balance and ice kinematics records are from McCall, Lemon Creek, and Black Rapids Glaciers. All of these glaciers have been profiled by Echelmeyer and Harrison. Mass balance at McCall Glacier was begun during the IGY, reinitiated during the IHD, and recently (1993 to present) by NSF grant to the University of Alaska Fairbanks (contact workshop participant Echelmeyer). There are both ice kinematics and some runoff data from McCall projects. Hydrologic balance measurements on Lemon Creek Glacier began during 1953 by the Juneau Icefield Research Project and basin runoff has been measured by the U.S. Geological Survey since 1951. The hydrologic balance data for Lemon Creek Glacier is discontinuous. Black Rapids Glacier mass balance and ice kinematics measurements began as a U.S. Geological Survey program during 1973 and are continuing at present by NSF grant to the University of Alaska Fairbanks (W.D. Harrison). Because NSF programs can not be perpetually extended, the surface-based observations sets at McCall and Black Rapids Glaciers will be discontinued unless alternate programs are identified. The most geographically comprehensive recent data are the unpublished surface altitude profiles of Keith Echelmeyer (workshop participant) and W.D. Harrison (University of Alaska Fairbanks, written communication).

Recognized glacier monitoring deficiencies in Alaska include: 1) Need to quantify mass balances on the large glaciers along the Gulf of Alaska where the mass fluxes are among the highest on Earth and where the largest glaciers exist; 2) extrapolate glacier-climate relations from the long-term measurement sites to typify regions; 3) thereby, define regions in which glacier activity may be represented by the activity measured at a single glacier; 4) thereby also identify under-sampled glacier systems; and 5) improve understanding of the details of the linkage between climate and glacier response.

Selected References

Hamilton, T.D., 1994, Late Cenozoic glaciation of Alaska, in Plafker, G., and Berg, H.C., eds., The geology of Alaska, v. G-1, The geology of North America: Geological Society of America, p. 813-844.

Mayo, L.R., 1984, Glacier mass balance and runoff research in the USA: Geografiska Annaler, v. 66A, no. 3, p. 215-227.

Molnia, B.F., and Krimmel, R.M., ____, Glaciers of Alaska; Glaciers of the United States (J-2); in Williams, R.S., Jr., and Ferrigno, J.G., eds., Satellite image atlas of glaciers of the world: U.S. Geological Survey Professional Paper 1386-J (Glaciers of North America), in press.

Snyder, E.F., 1996, Bibliography of glacier studies by the U.S. Geological Survey: U.S. Geological Survey Open-File Report 95-723, 35 p.