CGRG Bibliography of Canadian Geomorphology
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Author : Gardner, A.; and Sharp, M.
Date : 2005.
Title : Influence of atmospheric circulation changes on Canadian High Arctic glaciers.
Publication : Arctic Net 2005 Programme. Annual Scientific Meeting, December 13-16, 2005. Banff, Alberta
Issue :
Page(s) : 58-59.
Abstract
With increasing Arctic temperatures, and growing concerns over their impact on glaciers, ice sheets and sea level, it is important to investigate the regional-scale response of these ice masses to recent changes in atmospheric circulation. Long-term (>30 years) mass balance (MB) (accumulation minus ablation) records from glaciers in the Canadian High Arctic (> 75o N) were therefore analyzed in relation to indices of synoptic-scale climatic variability derived from National Centers for Environmental Prediction (NCEP) climate reanalysis fields. Seasonal and annual MB records (1963- 2001) were obtained for glaciers located on Axel Heiberg, Devon, Melville, and Meighen Islands (Dyurgerov, Meier et al. 2002). Since summer MB is the dominant source of variability in the annual MB of these glaciers (accounting for 90-98% of the variance in annual MB), the annual MB records were compared with indices of circulation variability for the summer months (JJA). Individual glacial MB records are poorly correlated (r = .23-.55) but they do display strong underlying similarities, which are suggestive of a large scale climatic signal that is partly masked by the effects of local scale meteorology and topography. Principal components analysis (PCA) was applied to the four time series to extract the primary mode of variance in the 4 datasets. The first principal component (PC1), which accounts for 56% of the variance in the MB records, was taken to be as representative of the regional climatic signal in Canadian High Arctic glacial MB. The time series of PC1 was compared with two major indices of northern hemisphere climate, the Arctic Oscillation (AO) (Thompson and Wallace 1998) and the North Atlantic Oscillation (NAO) (NOAA Climate Prediction Center), to determine whether any relationship existed between these indices and the MB records. The AO, the leading empirical orthogonal function of the northern hemisphere sea-level pressure field, shows no significant relationship with PC1 while the NAO, the standardized pressure difference between the Icelandic low and the Azores high shows a significant (but not strong) relationship, accounting for 20% of the variance in PC1. An index for the intensity of the summer northern circumpolar vortex, the dominant feature of the Arctic atmospheric circulation, was created by standardizing the summer 300mb geopotential heights derived from the NCEP reanalysis for a 5o by 5o box located over average position of the center of the300mb geopotential height minimum (82.5 - 87.5ON, 82.5 - 87.5OW) for the period 1963-2001. The 300mb geopotential height field was selected for development of this index as this level has been noted to best represent variations in the Arctic polar vortex (Angell 1998). Variations in the summer vortex index are well correlated with variations in summer atmospheric temperatures across the Canadian high Arctic, and account for 36% of the variance within the PC1. The polar vortex, as defined by the above index, provides a much stronger relationship to regional variations in Canadian High Arctic glacier mass balance than either the Arctic Oscillation (AO) or the North Atlantic Oscillation (NAO) and should be further developed as an index of climatic variability within the region.
Bibliography of Canadian Geomorphology