Abstract
ABSTRACTPredicting the velocity response of glaciers to increased surface melt is a major topic of ongoing research with significant implications for accurate sea-level rise forecasting. In this study we use optical and radar satellite imagery as well as comparisons with historical ground measurements to produce a multi-decadal record of ice velocity variations on Penny Ice Cap, Baffin Island. Over the period 1985–2011, the six largest outlet glaciers on the ice cap decelerated by an average rate of 21 m a−1 over the 26 year period (0.81 m a−2), or 12% per decade. The change was not monotonic, however, as most glaciers accelerated until the 1990s, then decelerated. A comparison of recent imagery with historical velocity measurements on Highway Glacier, on the southern part of Penny Ice Cap, shows that this glacier decelerated by 71% between 1953 and 2009–11, from 57 to 17 m a−1. The recent slowdown of outlet glaciers has coincided with increases in mass loss, terminus retreat and an inferred reduction in basal sliding. Measured decelerations are greater than the total short-term variability measured from both seasonal and interannual fluctuations, and support the hypothesis that glacier thinning and/or increased meltwater production promotes a long-term reduction in ice motion.
Highlights
High summer temperatures over the last few decades have resulted in sharply increased mass losses of glaciers and ice caps in the Canadian Arctic Archipelago (CAA), since 2005 (Gardner and others, 2011; Harig and Simons, 2016)
We present a multi-decadal record of ice velocity variations since the 1950s on Penny Ice Cap (PIC), the largest land ice mass on Baffin Island, using optical and radar remote sensing imagery updated to 2014, as well as comparisons of these data with earlier, historical field measurements
The synthetic aperture radar (SAR)-derived velocity map of PIC shows that most of the ice cap is slow-moving (
Summary
High summer temperatures over the last few decades have resulted in sharply increased mass losses of glaciers and ice caps in the Canadian Arctic Archipelago (CAA), since 2005 (Gardner and others, 2011; Harig and Simons, 2016). Observations of short-term, high velocity events on some parts of the Greenland ice sheet (GIS) in summer (Zwally and others, 2002) have led to concerns that accelerated ice motion may occur as the climate warms and surface melt rates increase. This could produce dynamic thinning (Alley and others, 2005) and greater drawdown of ice from the interior, resulting in increasing mass wasting rates in response to future warming (Parizek and Alley, 2004). Similar positive relationships between melt and short-term velocity variations have been observed on temperate and polythermal valley glaciers (Iken, 1981; Mair and others, 2003; Copland and others, 2003b)
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