Glaciological characteristics of the ablation zone of Baltoro glacier, Karakoram, Pakistan

Abstract

Baltoro glacier in the Karakoram, Pakistan, is one of the world's largest valley glaciers. It drains an area of about 1500 km 2 and is >60 km long. In 2004 an Italian/German expedition carried out a glaciological field program on the ablation zone of the glacier, focusing on the ablation conditions and the dynamic state of the glacier. As Baltoro glacier is a debris-covered glacier, ice ablation also depends on the debris properties. Stake measurements of ice ablation and debris cover in combination with meteorological data from automatic weather stations close by have been used to determine the local melt conditions. Results from these calculations have been combined with an analysis of different classes of surface cover and information about precipitation, using remote-sensing techniques, in order to calculate mass fluxes for the upper part of Baltoro glacier. The dynamic state of the glacier has been investigated by GPS-based surface velocity measurements along the stake network. A comparison of these short-term measurements during the melt season with surface velocities computed from feature tracking of satellite images shows a high seasonal variability of the ice motion. We have shown that this variability is up to 100% of the annual mean velocity. On the basis of these investigations, the mass fluxes at the Concordia cross-section have been quantified. This approach can now be used together with the ablation calculations to reconstruct the variability of glacier extent and volume in the past using available climate data from the central Karakoram. From the comparison of historical measurements and photographs it is shown that the snout of Baltoro glacier is oscillating back and forth a couple of hundred metres. Otherwise it seems not to react with the same magnitude as other glaciers to the climatic change. Elevation changes at Concordia are a few tens of metres at the most.

Observations: Cryosphere

“…In particular, there has been "a doubling in the number of new surges in the 14 years after 1990 (26 surges) than in the 14 years before 1990 (13 surges)." This increase in glacier surging correlates with the positive mass balances reported for the Karakoram by Gardelle et al (2011) and others over the past few decades and is consistent with the many other glaciological indicators of recent ice stability or expansion in this area reported by , Pecci and Smiraglia (2000), Mayer et al (2006), and Quincey et al (2009).…”

Future Hydrological Regimes in the Upper Indus Basin: A Case Study from a High-Altitude Glacierized Catchment

“…Mihalcea et al (2006) and Mayer et al (2006) evaluated melt factors for both debris-covered and debris-free ice, based on field ablation data from the Baltoro glacier. Mihalcea et al (2008) used remote sensing and field data to develop a debris thickness map of the Baltoro.…”

“…Specifically, the model uses a simplified ice flow approach, by shifting a proper quantity of ice from an altitude belt to the lower one. The large valley glaciers in the Karakoram flow with maximum speeds of about 100-150 m yr 21 , while the glacier tongues are on the order of 20-40 km long (e.g., Mayer et al 2006;Quincey et al 2011). Simulations of glacier runoff with periods of 50-100 years lead to an ice movement of 5-15 km, that is, less than half of the glacier tongue length.…”

“…The glacier mass balance budget in the Karakoram positively affected the 2003-08 specific mass balance for the entire HKH region, which was estimated by Kääb et al (2012) into 20.21 6 0.05 m yr 21 of water equivalent. In particular, some studies discuss the expansion and thickening of the largest glaciers, mainly in the central Karakoram, since the 1990s, accompanied by a nonnegligible number of rapid glacier advances (i.e., surge-type phenomena; see, e.g., Diolaiuti et al 2003;Hewitt 2005;Barrand and Murray 2006;Mayer et al 2011;Copland et al 2011;Minora et al 2013).…”

Climate–Glacier Dynamics and Topographic Forcing in the Karakoram Himalaya: Concepts, Issues and Research Directions

“…The Indian summer monsoon, which is a part of the larger Asian-Australian monsoon system [67], is also an important contributor to precipitation in the region [68,69]. A third synoptic-scale climate feature affecting the region is the Tibetan Anticyclone, which is strong during the summer and affects the intrusion of the Indian summer monsoon into the Karakoram Himalaya [70,71].…”