Skip to main content Accessibility help



  • Access
  • Cited by 26
  • Cited by
    This article has been cited by the following publications. This list is generated based on data provided by CrossRef.

    McMillan, Malcolm Nienow, Peter Shepherd, Andrew Benham, Toby and Sole, Andrew 2007. Seasonal evolution of supra-glacial lakes on the Greenland Ice Sheet. Earth and Planetary Science Letters, Vol. 262, Issue. 3-4, p. 484.

    Harper, Joel T. Humphrey, Neil F. Pfeffer, W. Tad and Lazar, Brian 2007. Two modes of accelerated glacier sliding related to water. Geophysical Research Letters, Vol. 34, Issue. 12,

    Bartholomaus, Timothy C. Anderson, Robert S. and Anderson, Suzanne P. 2008. Response of glacier basal motion to transient water storage. Nature Geoscience, Vol. 1, Issue. 1, p. 33.

    Arendt, Anthony A. Luthcke, Scott B. Larsen, Christopher F. Abdalati, Waleed Krabill, William B. and Beedle, Matthew J. 2008. Validation of high-resolution GRACE mascon estimates of glacier mass changes in the St Elias Mountains, Alaska, USA, using aircraft laser altimetry. Journal of Glaciology, Vol. 54, Issue. 188, p. 778.

    Price, S.F. Payne, A.J. Catania, G.A. and Neumann, T.A. 2008. Seasonal acceleration of inland ice via longitudinal coupling to marginal ice. Journal of Glaciology, Vol. 54, Issue. 185, p. 213.

    Lesemann, Jerome-Etienne and Brennand, Tracy A. 2009. Regional reconstruction of subglacial hydrology and glaciodynamic behaviour along the southern margin of the Cordilleran Ice Sheet in British Columbia, Canada and northern Washington State, USA. Quaternary Science Reviews, Vol. 28, Issue. 23-24, p. 2420.

    Arendt, Anthony Walsh, John and Harrison, William 2009. Changes of Glaciers and Climate in Northwestern North America during the Late Twentieth Century. Journal of Climate, Vol. 22, Issue. 15, p. 4117.

    Schuler, T. V. and Fischer, U. H. 2009. Modeling the diurnal variation of tracer transit velocity through a subglacial channel. Journal of Geophysical Research, Vol. 114, Issue. F4,

    Bartholomew, Ian Nienow, Peter Mair, Douglas Hubbard, Alun King, Matt A. and Sole, Andrew 2010. Seasonal evolution of subglacial drainage and acceleration in a Greenland outlet glacier. Nature Geoscience, Vol. 3, Issue. 6, p. 408.

    Bartholomew, I.D. Nienow, P. Sole, A. Mair, D. Cowton, T. King, M.A. and Palmer, S. 2011. Seasonal variations in Greenland Ice Sheet motion: Inland extent and behaviour at higher elevations. Earth and Planetary Science Letters, Vol. 307, Issue. 3-4, p. 271.

    Hoffman, M. J. Catania, G. A. Neumann, T. A. Andrews, L. C. and Rumrill, J. A. 2011. Links between acceleration, melting, and supraglacial lake drainage of the western Greenland Ice Sheet. Journal of Geophysical Research, Vol. 116, Issue. F4,

    Sundal, Aud Venke Shepherd, Andrew Nienow, Peter Hanna, Edward Palmer, Steven and Huybrechts, Philippe 2011. Melt-induced speed-up of Greenland ice sheet offset by efficient subglacial drainage. Nature, Vol. 469, Issue. 7331, p. 521.

    Gades, Anthony M. Raymond, Charles F. and Conway, Howard 2012. Radio-echo probing of Black Rapids Glacier, Alaska, USA, during onset of melting and spring speed-up. Journal of Glaciology, Vol. 58, Issue. 210, p. 713.

    Shugar, Dan H. Rabus, Bernhard T. Clague, John J. and Capps, Denny M. 2012. The response of Black Rapids Glacier, Alaska, to the Denali earthquake rock avalanches. Journal of Geophysical Research: Earth Surface, Vol. 117, Issue. F1, p. n/a.

    Podrasky, David Truffer, Martin Fahnestock, Mark Amundson, Jason M. Cassotto, Ryan and Joughin, Ian 2012. Outlet glacier response to forcing over hourly to interannual timescales, Jakobshavn Isbræ, Greenland. Journal of Glaciology, Vol. 58, Issue. 212, p. 1212.

    Mair, Douglas 2012. Glaciology. Progress in Physical Geography, Vol. 36, Issue. 6, p. 813.

    Burgess, Evan W. Larsen, Christopher F. and Forster, Richard R. 2013. Summer melt regulates winter glacier flow speeds throughout Alaska. Geophysical Research Letters, Vol. 40, Issue. 23, p. 6160.

    Mernild, Sebastian H. Knudsen, Niels T. Hoffman, Matthew J. Yde, Jacob C. Hanna, Edward Lipscomb, William H. Malmros, Jeppe K. and Fausto, Robert S. 2013. Volume and velocity changes at Mittivakkat Gletscher, southeast Greenland. Journal of Glaciology, Vol. 59, Issue. 216, p. 660.

    Luthcke, Scott B. Rowlands, D.D. Sabaka, T.J. Loomis, B.D. Horwath, M. and Arendt, A.A. 2014. Remote Sensing of the Cryosphere. p. 231.

    Melkonian, Andrew K. Willis, Michael J. and Pritchard, Matthew E. 2014. Satellite-derived volume loss rates and glacier speeds for the Juneau Icefield, Alaska. Journal of Glaciology, Vol. 60, Issue. 222, p. 743.



      • Send article to Kindle

        To send this article to your Kindle, first ensure is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about sending to your Kindle. Find out more about sending to your Kindle.

        Note you can select to send to either the or variations. ‘’ emails are free but can only be sent to your device when it is connected to wi-fi. ‘’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

        Find out more about the Kindle Personal Document Service.

        Record negative glacier balances and low velocities during the 2004 heatwave in Alaska, USA: implications for the interpretation of observations by Zwally and others in Greenland
        Available formats

        Send article to Dropbox

        To send this article to your Dropbox account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Dropbox.

        Record negative glacier balances and low velocities during the 2004 heatwave in Alaska, USA: implications for the interpretation of observations by Zwally and others in Greenland
        Available formats

        Send article to Google Drive

        To send this article to your Google Drive account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Google Drive.

        Record negative glacier balances and low velocities during the 2004 heatwave in Alaska, USA: implications for the interpretation of observations by Zwally and others in Greenland
        Available formats
Export citation

Following the hot summer of 2003 in Europe, Alaska, USA, experienced its own heatwave in the summer of 2004. Hot and dry conditions were caused by an unusually persistent high-pressure ridge over most of the state. Fairbanks experienced the warmest summer on record, with temperatures 2.8°C above normal, and many other communities experienced record highs ( The hot and dry conditions created the worst fire season on record, with over 27 000 km2 of burned area (

The United States Geological Survey (USGS) has measured summer, winter and net mass balances of Gulkana Glacier, Alaska, since 1966 ( In eight of these years the mass balance was positive;the last of these was 1985 (Fig. 1). The year 2004 set a record negative net balance, –2.29 m, or about 3 standard deviations below normal. Winter balance for 2004 was about 1 standard deviation below normal and so contributed to the negative year, but the hot summer was the main contributor. The balance gradient was also a record high, about 1.3 m(100 m–1. Temperatures are measured at a site on the eastern lateral moraine of the glacier at 1480m a.s.l. Summer temperatures (16 May to 30 August) for 2004 set a record high and were about 3°C above normal. A stream gauge in the outlet river showed annual run-off almost twice normal and again a new record, about 3.5 standard deviations above normal. About 40% of the annual run-off was due to shrinkage of the glacier.

Fig. 1 Gulkana Glacier mass balance. The 2004 winter balance was relatively lower than the mean, but not by much. However, the summer and net balances were the most negative in the record.

On nearby Black Rapids Glacier specific mass balances have been measured since 1973 (Heinrichs and others, 1996). During the first two decades both winter and summer balances were measured, but more recently the glacier was visited only once a year, yielding net specific mass balances. Two sites have complete records, one in the accumulation area (8 km site) and one in the upper ablation area (14 km site). Glacier-wide mass balances have never been calculated, because the extrapolation of the specific balances to the complicated geometry is difficult. The glacier-wide balance has been further complicated by a massive rockfall that covered more than 10 km2 of the glacier’s ablation area in November 2002 (Truffer and others, 2002). Nevertheless, the two datasets of specific mass balances show the most negative balances since measurements began (Fig. 2). The 8 km site had a negative balance of 1.20 m w.e., only the third negative measurement in 32 years. An inspection of a moderate-resolution imaging spectroradiometer (MODIS) satellite image of 22 August ( for the Alaska Range confirms the picture of widespread melt. Only the very highest areas of most glaciers retained a snow cover.

Fig. 2 Specific net balances in the lower accumulation and upper ablation area of Black Rapids Glacier. Both sites witnessed the most negative balance in the 32 year record. Dashed lines show zero specific balance.

Mean annual velocities have also been measured at these index sites and have been observed to vary by more than 50% (Fig. 3). It is interesting to note that the velocities between May 2004 and May 2005 were among the lowest in the 32 year record, despite record run-off at the nearby Gulkana Glacier, and record ice loss at Black Rapids Glacier (where run-off is not measured). Heinrichs and others (1996) showed that the variation in glacier motion cannot be explained by the effect of thickness changes on ice deformation. The thickness change during the last three years of decreasing velocities was only –2.0 m at 14 km and –1.2 m at 8 km. The total ice thickness at both locations is ~600 m. The average surface slope between 8 km and 20 km has remained constant during that time. Consequently, the velocity variation has to be caused by variations in basal motion. Black Rapids Glacier has surged in the past, but our velocity data do not point to an imminent surge. Instead they are dominated by a roughly decadal variation (Fig. 3). On the basis of a field study, Raymond and others (1995) pointed out that there is no difference in subglacial hydraulics between Black Rapids Glacier and the nearby non-surge Fels Glacier that could not be explained by the difference in glacier size. It can thus be assumed that the velocity variations shown here are not primarily a result of surge dynamics. The low 2004 velocities can tentatively be explained by the establishment of effective water drainage networks in times of high runoff, which tends to concentrate subglacial discharge into a few big channels (e.g. Fountain and Walder, 1998). This can lead to reduced basal motion, an observation often made late in summer, when water discharge is high and speed relatively low.

Fig. 3 Mean annual velocities of two sites on Black Rapids Glacier. Note the relatively low velocities in 2004/05.

Observations such as these caution against the use of simple run-off/basal motion relationships, as suggested by Zwally and others (2002) and recently used in ice sheet modeling (e.g. Parizek and Alley, 2004). Those measurements were made on a temperate-based ice sheet near an outlet glacier. While the glaciological setting is different, there should be no fundamental reason why basal motion would react differently to water input than it does in a valley glacier setting. To clarify, we do not doubt the accuracy of the measurements made by Zwally and others. Most temperate glaciers are known to undergo a transient speed-up when water input increases in spring and encounters an underdeveloped drainage system. We do caution, however, against extrapolating an overly simple run-off/motion relationship.


We acknowledge the work of those who were instrumental in establishing and maintaining the monitoring networks, in particular L. Mayo, D. Trabant and K. Echelmeyer. Much of the Black Rapids work has been done in conjunction with US National Science Foundation-funded work, most recently NSF OPP-0115819.


Fountain, A.G. and Walder, J.S. 1998 Water flow through temperate glaciers. Rev. Geophys., 36(3), 299328.
Heinrichs, T.A., Mayo, L.R. Echelmeyer, K.A. and Harrison, W.D. 1996 Quiescent-phase evolution of a surge-type glacier: Black Rapids Glacier, Alaska, USA. J. Glaciol., 42(140), 110122.
Parizek, B.R. and Alley, R.B. 2004 Implications of increased Greenland surface melt under global-warming scenarios: ice- sheet simulations. Quat. Sci. Rev., 23(9–10), 10131027.
Raymond, C.F., Benedict, R.J. Harrison, W.D. Echelmeyer, K.A. and Sturm, M. 1995 Hydrological discharges and motion of Fels and Black Rapids Glaciers, Alaska, USA: implications for the structure of their drainage systems. J. Glaciol., 41(138), 290304.
Truffer, M., Craw, P., Trabant, D. and March, R. 2002 Effects of the M7.9 Denali Fault Earthquake on glaciers in the Alaska Range. EOS Trans., AGU, 83(47), Fall Meet. Suppl., Abstract S72F-1334.
Zwally, H.J., Abdalati, W., Herring, T., Larson, K., Saba, J. and Steffen, K. 2002 Surface melt-induced acceleration of Greenland ice-sheet flow. Science, 297(5579), 218222.