Surface speed and frontal ablation of Kronebreen and Kongsbreen, NW Svalbard, from SAR offset tracking

Abstract

Abstract. Kronebreen and Kongsbreen are among the fastest-flowing glaciers on Svalbard and, therefore, important contributors to the total dynamic mass loss from the archipelago. Here, we present a time series of area-wide surface velocity fields from April 2012 to December 2013 based on offset tracking on repeat high-resolution Radarsat-2 Ultrafine data. Surface speeds reached up to 3.2 m d−1 near the calving front of Kronebreen in summer 2013 and 2.7 m d−1 at Kongsbreen in late autumn 2012. Additional velocity fields from Radarsat-1, Radarsat-2 and TerraSAR-X data since December 2007 together with continuous GPS measurements on Kronebreen since September 2008 revealed complex patterns in seasonal and interannual speed evolution. Part of the ice-flow variations seem closely linked to the amount and timing of surface meltwater production and rainfall, both of which are known to have a strong influence on the basal water pressure and hence basal lubrication. In addition, terminus retreat and the associated reduction in back stress appear to have influenced the speed close to the calving front, especially at Kongsbreen in 2012 and 2013. Since 2007, Kongsbreen retreated up to 1800 m, corresponding to a total area loss of 2.5 km2. In 2011 the retreat of Kronebreen of up to 850 m, responsible for a total area loss of 2.8 km2, was triggered after a phase of stable terminus position since ~ 1990. Retreat is an important component of the mass balance of both glaciers, in which frontal ablation is the largest component. Total frontal ablation between April 2012 and December 2013 was estimated to 0.21–0.25 Gt a−1 for Kronebreen and 0.14–0.16 Gt a−1 for Kongsbreen.

Effects of undercutting and sliding on calving: a global approach applied to Kronebreen, Svalbard

“…The glacier front position undergoes seasonal oscillations, showing advance during the winter and spring followed by retreat in the summer and autumn. Since 2011, the summer retreat has outpaced the winter advance, with an overall net retreat of ∼ 2 km between 2011 and 2015 after a relatively stable period since the 1990s (Schellenberger et al, 2015;Luckman et al, 2015;Köhler et al, 2016). Velocities at the front can reach 5 m d −1 in the summer with large seasonal and annual variations associated with basal sliding velocity .…”

Multi-year surface velocities and sea-level rise contribution of the Basin-3 and Basin-2 surges, Austfonna, Svalbard

“…As with the velocity maps, we closely follow the approaches used in Schellenberger et al (2015) and Dunse et al (2015) to estimate the frontal ablation A f . This procedure can be divided in two steps: the calculation of the ice mass flux through a fluxgate q fg and the glacier mass changes at the terminus q t due to advance or retreat.…”

“…In this study, we closely follow the processing steps of Schellenberger et al (2015) and Dunse et al (2015) to derive glacier surface velocity of Basin-3 and Basin-2 by means of SAR offset and speckle tracking. The time-series of velocity maps from Table 1.…”

Using SAR satellite data time-series for regional glacier mapping

“…Kongsvegen (108 km 2 ) surged in 1948 (Melvold and 10 Hagen, 1998) and is currently in its quiescent phase with low flow velocities (Nuth et al, 2012). Kronebreen (108 km 2 ), the lower part of Holtedahlfonna (295 km 2 ), is a fast-flowing tidewater glacier with maximum ice velocity of 3.2 m d −1 at the calving front (Schellenberger et al, 2015). …”