Mountain Glaciers and Ice Caps (Outside Greenland)
M. Sharp1, G. Wolken2, M.-L. Geai1, D. Burgess3
1University of Alberta, Department of Earth and Atmospheric Sciences
2Alaska Division of Geological & Geophysical Surveys
3Geological Survey of Canada, National Glaciology Program
With data contribution from J.G. Cogley
November 9, 2012
- In 2009-2010, the most recent balance year for which data are available for the twenty Arctic glaciers reported by the World Glacier Monitoring Service (WGMS), nineteen glaciers had a negative mass balance.
- In the 2010-2011 balance year, the mass losses from the four Canadian Arctic glaciers reported by the WGMS were the greatest in records that are between 49 and 52 years long.
- The GRACE-derived mass loss (96±49 Gt) in 2010-11 from all the glaciers and ice caps in the Canadian Arctic Islands was the largest for this region since GRACE observations began in 2002.
Mountain glaciers and ice caps in the Arctic, with an area of over 400,000 km2, contribute significantly to global sea level change (Meier et al., 2007; Gardner et al., 2011; Jacob et al., 2012). They lose mass by iceberg calving, and by surface melt and runoff. The climatic mass balance (Bclim, the difference between annual snow accumulation and runoff) is an index of how they respond to climate change and variability. Note that Bclim is a new term (Cogley et al., 2011) synonymous with net mass balance (Bn) used in previous Arctic Report Cards (e.g., Sharp and Wolken, 2011).
Measurements of Bclim of 27 Arctic glaciers have been published for 2009-2010 (World Glacier Monitoring Service, 2012). These are located in Alaska (three), Arctic Canada (four), Iceland (nine), Svalbard (four), Norway (two) and Sweden (5) (Fig. 5.5, Table 5.1). All but one of these glaciers (Kongsvegen in Svalbard) had a negative annual balance. Mass balances of glaciers in Iceland, Gulkana Glacier in interior Alaska, and several glaciers in northern Scandinavia were extremely negative in 2009-2010. In the Canadian Arctic, the 2009-2010 balances of the Devon and Melville Island South ice caps were the 4th and 3rd most negative within the 51- and 49-year records, respectively (Table 5.1).
|Region||Glacier||Net Balance 2009-10
(kg m-2 yr-1)
|Net Balance 2010-11
(kg m-2 yr-1)
|Arctic Canada||Devon Ice Cap||-417||-683|
|Meighen Ice Cap||-387||-1310|
|Melville S. Ice Cap||-939||-1339|
|Iceland||Langjökull S. Dome||-3800|
Bclim data for 2010-2011 are only available for the four glaciers in the Canadian High Arctic (Table 5.1). That year, Bclim values were the most negative on record for all four glaciers. In the Canadian Arctic, between 5 and 9 of the most negative mass balance years in the 49-52 year record have occurred since 2000. The mean annual mass balance for the period 2000-2011 is between 3 (Melville South Ice Cap) and 8 (Meighen Ice Cap) times as negative as the 1963-1999 average for each ice cap. This is a result of strong summer warming over the region that began around 1987 (Gardner and Sharp, 2007) and accelerated significantly after 2005 (Sharp et al. 2011). This trend is clearly evident in all the mass balance records shown in Fig. 5.6. The scale of the accelerating mass loss seen in Fig. 5.6 is illustrated by a comparison of the mean loss for the four glaciers in three periods of the record: -575.3 kg m-2 a-1 in 2005-2011; -218.8 kg m-2 a-1 in 1995-2002; -184.9 kg m-2 a-1 in 1989-1994.
In 2010-11, the estimated mass loss from all the glaciers and ice caps in the Canadian Arctic Islands was -96±49 Gt (Sharp and Wolken, 2012). Derived using GRACE satellite gravimetry, this estimate of the complete mass balance, ΔM, which includes mass losses by iceberg calving, was the most negative value for this region during the GRACE observation period, 2002-2011. In the previous balance year, 2009-2010, the GRACE-derived ΔM estimate for this region was -73±55 Gt, and the mean annual value for the period 2004-2009 was -63 Gt (Sharp and Wolken, 2012). The large Bclim values reported in the previous paragraph are consistent with the increasing GRACE-derived ΔM estimates, which confirm the growing importance of glaciers and ice caps in the Canadian Arctic Islands as contributors to global sea level rise (Gardner et al., 2011).
Variability in mean summer temperature accounts for much of the inter-annual variability in Bclim in cold, dry regions like the Canadian high Arctic while, in more maritime regions, like Iceland and southern Alaska, variability in winter precipitation is also a factor. Land surface temperature (LST) over ice in summer is likely closely related to Bclim. Fig. 5.7 shows moderate to large LST anomalies over glaciers and ice caps throughout the Arctic, particularly in summers 2011 and 2012 in the Canadian high Arctic (northern Ellesmere, Agassiz, Axel Heiberg, Prince of Wales). More generally in 2011 (and 2012), glacier mass balance in the Canadian high Arctic was affected by the same atmospheric circulation and advection of warm air into the region that caused significant melting on the Greenland ice sheet (Sharp and Wolken, 2011; Tedesco et al., 2012).
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Sharp, M., D. O. Burgess, J. G. Cogley, M. Ecclestone, C. Labine and G. J. Wolken. 2011. Extreme melt on Canada's Arctic ice caps in the 21st century. Geophys. Res. Lett., 38, L11501, doi:10.1029/2011GL047381.
Tedesco, M., J. E. Box, J. Cappellen, T. Mote, R. S. W. van der Wal and J. Wahr. 2012. Greenland Ice Sheet. [in State of the Climate in 2011], Bull. Amer. Meteorol. Soc., 93(7), S150-S153.
World Glacier Monitoring Service. 2012. Preliminary glacier mass balance data 2009 and 2010. http://www.geo.uzh.ch/microsite/wgms/mbb/sum10.html. Accessed September 29, 2012.