Changes in glacier surface cover on Baltoro glacier, Karakoram, north Pakistan, 2001–2012

Abstract

The presence of supraglacial debris on glaciers in the Himalaya-Karakoram affects the ablation rate of these glaciers and their response to climatic change. To understand how supraglacial debris distribution and associated surface features vary spatially and temporally, geomorphological mapping was undertaken on Baltoro Glacier, Karakoram, for three timeseparated images between 2001-2012. Debris is supplied to the glacier system through frequent but small landslides at the glacier margin that form lateral and medial moraines and less frequent but higher volume rockfall events which are more lobate and often discontinuous in form. Debris on the glacier surface is identified as a series of distinct lithological units which merge downglacier of the convergence area between the GodwinAusten and Baltoro South tributary glaciers. Debris distribution varies as a result of complex interaction between tributary glaciers and the main glacier tongue, complicated further by surge events on some tributary glaciers. Glacier flow dynamics mainly controls the evolution of a supraglacial debris layer. Identifying such spatial variability in debris rock type and temporal variability in debris distribution has implications for glacier ablation rate, affecting glacier surface energy balance. Accordingly, spatial and temporal variation in supraglacial debris should be considered when determining mass balance for these glaciers through time. ARTICLE HISTORY

Supraglacial ice cliffs and ponds on debris-covered glaciers: spatio-temporal distribution and characteristics

“…This suggests that it is the average size of cliffs that increases in the melt season. Ponded area accounts for less than 1.1% (±0.2%) of the debris-covered area in all dry seasons and increases up to 2.1% (±0.4%) during the wetter seasons when ponds fill (Miles andothers, 2016, 2017b). Contrary to ice cliffs it is the number of ponds that increases in the wetter seasons suggesting new formations with increased melting activity (Table 3).…”

Temporal variations in supraglacial debris distribution on Baltoro Glacier, Karakoram between 2001 and 2012

“…The greatest percentage change in supraglacial water body number (73 %) and area (171 %) occurred between 2001 and 2004. Increase in supraglacial water body area and number has previously been attributed to changes in precipitation since 2000 (Quincey et al, 2009;Gibson et al, 2016).…”

“…The debris layer is thinnest (0.01-0.15 m) in the upper ablation area of the glacier and exceeds 1 m at the glacier terminus (Mihalcea et al, 2008b). Supraglacial debris units have differing lithologies across the debris-covered glacier surface, which include granite, schist, gneiss and metasediments (Gibson et al, 2016). …”

“…The supraglacial debris on Baltoro Glacier was dominated by gneiss (~51-53 % of the debris-covered glacier area), whilst ~47-49 % was composed of granite (~27 %), schist (~12 %) and a small proportion of metasediment (~6 %) ( Figure 5, Table 3). Across the main glacier tongue, negligible change in debris unit boundaries occurred between 2001 and 2012 and change in percentage cover of debris units was attributed to errors produced by manual digitisations (Gibson et al, 2016; Table 3). in the lower section of the glacier corresponded to the location of supraglacial water bodies.…”

Evaluating Glacier Dynamics Using Temporal Remote Sensing Images: A Case Study of Hunza Valley, Northern Pakistan

“…Bocchiola and Diolaiuti (2013) and Hewitt (2005) observed that the glaciers in the central and eastern Himalayas, Hindu-Kush and Karakoram, shows different trends of advance, stable or retreat, which is known as "Karakoram Anomaly". This anomalous behavior can be attributed to supra glacier debris cover and lack of mass balance data (Gibson et al, 2017;Scherler et al, 2011a). Aim of this study is to evaluate the temporal dynamics of glaciers using the Landsat images and weather data, in northern Pakistan.…”