Interannual modulation of seasonal glacial velocity variations in the Eastern Karakoram detected by ALOS-1/2 data

Abstract

Unlike in most other regions, Karakoram glaciers are either stable or advancing, a phenomenon known as the Karakoram anomaly. Despite studies of glacier surges and the derivation of surface velocity maps, the spatiotemporal variability of glacier dynamics still remains poorly understood, particularly in the Eastern Karakoram Range. We use Advanced Land Observing Satellite/the Phased Array type L-band Synthetic Aperture Radar (ALOS/PALSAR)-1/2 data from 2007 to 2011 and 2014 to 2015 to examine detailed surface velocity patterns of the Siachen, Baltoro, Kundos, Singkhu and Gasherbrum Glaciers. The first three glaciers show considerable velocity variability (20–350 m a−1), with clear seasonal patterns. Although all glaciers, except for Baltoro, flow slowest in 2015, the velocity structures are individual and vary in space and time. In Gasherbrum Glacier, peak surge-phase velocities are seasonally modulated, with maxima in summers 2006 and 2007, suggesting surface melt plays an important role in maintaining the active phase. Given the relatively close proximity of these glaciers, we assume that surface melt timing and rates are comparable. We therefore argue that the observed spatiotemporal and interannual velocity patterns are determined by local and internal mechanisms, including englacial and subglacial hydrology, thermal processes and tributary configuration of each individual glacier.

Glacier surges in the north-west West Kunlun Shan inferred from 1972 to 2017 Landsat imagery

“…Finally, glaciers 3 and 6 displays increase in observed velocity during the summer months. This has been similarly observed for surge-type glaciers in the Karakoram (Mayer and others, 2011; Quincey and others, 2015; Round and others, 2017; Usman and Furuya, 2018). Seasonal variations in velocity are indicative of an active subglacial hydrological system, and as such should be indicative of a hydrological surge.…”

Karakoram geodetic glacier mass balances between 2008 and 2016: persistence of the anomaly and influence of a large rock avalanche on Siachen Glacier

“…The length of the depression is 1.2 km and its width ~300 m if we consider the region where the elevation changes are more negative than −100 m. The depression reaches its maximum depth in 2015 and starts to fill in afterward. The shape of the depression evolves with time, a consequence of relatively fast glacier flow (~150 m a −1 at this location) and the strong velocity gradient at these shear margins (Usman and Furuya, 2018; Dehecq and others, 2019). We note that our volume change estimates for the different periods do not take into account the effect of the displacement of topographic features due to glacier flow.…”

Characterizing the surge behavior of Alakesayi Glacier in the West Kunlun Shan, Northwestern Tibetan Plateau, from remote-sensing data between 2013 and 2018

“…High Mountain Asia (HMA) hosts the largest glacier concentration outside the polar regions. In HMA, some glaciers surging in the Karakoram and West Kunlun regions have been identified by satellite remote sensing (Copland and others, 2011; Yasuda and Furuya, 2013, 2015; Quincey and others, 2015; Bhambri and others, 2017; Usman and Furuya, 2018; Chudley and Willis, 2019), but comprehensive study of surge behaviors in this area is still limited. In this letter, by utilizing remote-sensing data, we are able to estimate and present the changes in surface velocity, terminus, morphological features and glacier thickness of Alakesayi Glacier during its recent surge and thus expand the knowledge of Alakesayi Glacier surge dynamics.…”