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TitleFirn profile changes in response to extreme 21st-century melting at Devon Ice Cap, Nunavut, Canada
AuthorBezeau, P; Sharp, M; Burgess, D; Gascon, G
SourceJournal of Glaciology vol. 59, no. 217, 2013 p. 981-991,
Alt SeriesEarth Sciences Sector, Contribution Series 20120439
Mediapaper; on-line; digital
File formatpdf
NTS48H/05; 48H/06
AreaDevon Island; ueen Elizabeth Islands
Lat/Long WENS -83.5000 -82.0000 75.5000 75.2500
Subjectssurficial geology/geomorphology; environmental geology; stratigraphy; glacial deposits; glacial history; glaciation; glaciology; ice; icefields; ice thickness; ice conditions; climate, arctic; climatic fluctuations; climate; snow; Devon Ice Cap; Cenozoic; Quaternary
Illustrationslocation maps; stratigraphic columns; tables; plots
ProgramProgram Coordination - Climate Change Science, Climate Change Geoscience
AbstractEstimating regional-scale rates of glacier mass change from repeat airborne and satellite altimetry requires assumptions about the density of the material being added to, or removed from, the glacier surface. This may vary in both space and time, especially in a period of warming climate such as has occurred in Arctic Canada since 2005. Here we compare firn properties measured on 20 shallow cores recovered from elevations of 1400 - 1900ma.s.l. on Devon Ice Cap in 2012 with equivalent measurements from 34 cores recovered from the same locations between 2004 and 2011. The average density of the top 2.5m of the firn column has increased by 13 - 80%. As a result, measured rates of density increase in the top 1.25mw.e. of the firn layer have likely thinned this layer at rates of 0.021 - 0.168ma -1
over the period 2004 - 12. These thinning rates are significant relative to local rates of surface height change measured by repeat airborne laser altimetry between 2004 and 2012 (-0.077 to -0.252ma -1) and indicate that, during periods of climate warming or cooling, firn densification rate changes must be taken into account when estimating mass change rates from measured height changes.
Summary(Plain Language Summary, not published)
Near surface layers (<60m) of the high elevation regions (>1400m a.s.l.) across the Canadian Arctic ice caps are composed primarily of firn, which is snow and/or low density porous ice greater that has survived at least 1 summer season. Through analysis of 34 shallow firn cores, firn temperature, and air temperature collected from the Devon Ice Cap, this study has documented a 13-80% increase in density and temperature of the near-surface firn over the past 7 years in response to rapid climate warming since 2005. These changes all indicate higher melt rates and increased infiltration and refreezing of meltwater within the firn layer. This strongly suggests that surface height decreases may be attributed to accelerated firn densification rather than to mass loss, and that changes in the rate of firn densification must be taken into account when estimating mass change rates of ice caps from geodetic surveillance methods.