ABSTRACT: A first complete inventory, areal measurement and change detection of northern Labrador glaciers.

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Abstract

A total of 59 active glaciers have been mapped from 2005 colour aerial photographs between latitude 58° 40’ and 59° 50’ North in the Torngat Mountains of northern Labrador. The glaciers ranged in size from 0.06 to 1.88 km2 for a total glacier area of 21.2 km2. Most of the glaciers (64%) are smaller than 0.25 km2 and only 2 are larger than 1 km2. Glaciers typically occupy cirque basins with high backwalls and many are heavily debris-covered at lower elevations. Glacier mapping from 2007 SPOT5 HRS satellite imagery revealed a total of 59 glaciers covering an area of 16.66 km2 and ranging in size from 0.05 to 1.24 km2. This represents a decline of 4.54 km2 or 21.4% of the 2005 area. Forty-nine or 83% of the glaciers experienced an areal decrease, with an average decline of 0.1 km2. The other 17% grew in area by an average of 0.02 km2. Six glaciers recorded a change in area of less than 0.01 km2, which given the spatial resolution of the imagery likely means anundetectable change. Of the glaciers that recorded growth, 6 were among the ten smallest glaciers in the Torngat Mountains having an area less than 0.35 km2. Meanwhile, three of the six largest glaciers experienced the greatestdecline in area, with the largest glacier – Superguksoak Glacier (1.88 km2) – suffering the greatest loss (0.64 km2). The 21% reduction in the areal extent of Torngat Mountain glaciers between 2005 and 2007 is dramatic, but needs to be viewed in the context of long-term trends in areal extent and climate. A study of 1950-60s glacier extent is in progress and preliminary analysis of a subset of 27 glaciers (0.06-1.28 km2) suggests that between 1950 and 2005 four glaciers melted completed or became too small to be actively fl owing and the total areal extent of the 27 glaciers had declined by one-third. Of the 23 glaciers that had persisted to 2007, the total areal decrease over the 57-year period is 40%, more than one-quarter of which occurred in the two years prior to 2007. NCEP/NCAR Reanalysis data (at the 700 kPa level to approximate glacierelevations) for the period 1998-2007 for the Nachvak Fiord region indicates an anomalously warm decade compared to the average summer temperature conditions for the past 60 years. In fact, 2007 was the second warmest summer on record, surpassed only by 2008, which was 2.57°C warmer than the 60-year average. The 1960s was an anomalously cold period with persistent below-normal temperatures. Winter precipitation (NMC Reanalysis data from the 700 kPa level) for 2005-2007 was above average for the past 60 years or so; but perhaps of greater relevance was the extended period of below-average precipitation since 1983 (16 of 22 years) and for 5 of the 7 years prior to 2005. In contrast, 60% of the winters between 1949 and 1982 had above-normal winter precipitation. In the absence of annual mass balance data, only very general correlations can be made between past climate and changes in glacier area. The long term decline in areal extent may be a glaciological response to general warming since the Little Ice Age; the dramatic recent decline in areal extent, however, may be primarily a response to a multi-decadal trend towards lower winter precipitation, coupled with anomalously warm summers.

Bibliography of Canadian Geomorphology