Interannual changes of the floating ice shelf of Petermann Gletscher, North Greenland, from 2000 to 2012

Andreas Münchow,Laurie Padman,Helen A Fricker

doi:10.3189/2014jog13j135

Abstract

AbstractPetermann Gletscher, northwest Greenland, drains 4% of the Greenland ice sheet into Nares Strait. Its floating ice shelf retreated from 81 to 48 km in length during two large calving events in 2010 and 2012. We document changes in the three-dimensional ice-shelf structure from 2000 to 2012, using repeated tracks of airborne laser altimetry and ice radio-echo sounding, ICESat laser altimetry and MODIS visible imagery. The recent ice-shelf velocity, measured by tracking surface features between flights in 2010 and 2011, is ~1.25 km a−1, ~15–30% faster than estimates made before 2010. The steady- state along-flow ice divergence represents 6.3 Gta−1mass loss through basal melting (~5Gta−1) and surface melting and sublimation (~1.0Gta−1). Airborne laser altimeter data reveal thinning, both along a thin central channel and on the thicker ambient ice shelf. From 2007 to 2010 the ice shelf thinned by ~5 m a−1, which represents a non-steady mass loss of ~4.1 Gta−1. We suggest that thinning in the basal channels structurally weakened the ice shelf and may have played a role in the recent calving events.

Highlights

Greenland’s tidewater glaciers are losing mass, through thinning and retreat, at an increasing rate (Joughin and others, 2010a; Howat and others, 2011; Bjørk and others, 2012)
The surface evolution of Petermann Gletscher (PG) and the ice islands it calved are recorded by Moderate Resolution Imaging Spectroradiometer (MODIS) imagery from the summers of 2003, 2010 and 2012 (Fig. 1)
Our estimate of ice flow speed for the floating ice shelf is $30% higher than those by Higgins (1991) for the late 20th century and Rignot and Steffen (2008) for 2002/03, but falls within the range of values given by Nick and others (2012) and Johannessen and others (2013) for the 2006–11 period

Summary

Introduction

Greenland’s tidewater glaciers are losing mass, through thinning and retreat, at an increasing rate (Joughin and others, 2010a; Howat and others, 2011; Bjørk and others, 2012). Over the past decade there has been a general clockwise progression of mass loss (Khan and others, 2010; Chen and others, 2011), with initial retreat in southeastern Greenland (Luckman and others, 2006; Howat and others, 2008) followed by loss in the southwest (Joughin and others, 2004) and, most recently, in northwest Greenland (Khan and others, 2010). In addition to this general trend, there is significant spatial and temporal variability of glacier mass budgets that does not always correlate with readily observed surface forcing (Howat and others, 2011; Moon and others, 2012). The total annual discharge at the grounding line is 12 Æ 1 Gt a–1

Results

Discussion

Conclusion