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ABSTRACT. Three debris-free glaciers with strongly differing annual glaciological glacier-wide mass balances (MBs) are monitored in the Everest region (central Himalaya, Nepal). The mass budget of Mera Glacier (5.1 km 2 in 2012), located in the southern part of this region, was balanced during 2007-15, whereas Pokalde (0.1 km 2 in 2011) and West Changri Nup glaciers (0.9 km 2 in 2013), ∼30 km further north, have been losing mass rapidly with annual glacier-wide MBs of −0.69 ± 0.28 m w.e. a −1 (2009-15) and −1.24 ± 0.27 m w.e. a −1 (2010-15), respectively. An analysis of high-elevation meteorological variables reveals that these glaciers are sensitive to precipitation, and to occasional severe cyclonic storms originating from the Bay of Bengal. We observe a negative horizontal gradient of annual precipitation in south-to-north direction across the range (≤−21 mm km −1 , i.e. −2% km −1 ). This contrasted mass-balance pattern over rather short distances is related (i) to the low maximum elevation of Pokalde and West Changri Nup glaciers, resulting in years where their accumulation area ratio is reduced to zero and (ii) to a steeper vertical gradient of MB for glaciers located in the inner arid part of the range.

[1] We present a new type of flow model suitable for Antarctic blue ice areas, with application to dating ice for paleoclimate purposes. The volume conserving model uses field data for surface velocities, mass balance and ice thickness along a flow line, with parameterized variation of ice rheology with depth to produce particle trajectories and isochrones. The model is tested on the contrasting Allan Hills Near Western Ice Field and the Scharffenbergbotnen blue ice fields in Antarctica by comparing predicted ages with ages inferred from meteorites and 14 C data. During the glacial periods, ice surface velocities at the Allan Hills must have been 25% less, and accumulation rates 50% less than present day values in order to match meteorite ages. In contrast, Scharffenbergbotnen velocities have probably been fairly constant over time due to the atypical valley where it resides.

[1] A fast-flowing tributary of Recovery ice stream penetrates more than 500 km into the interior of East Antarctica. Recent satellite-based studies found surface features in the onset area of this tributary that indicate a significant subglacial hydraulic system, including four large smooth basins, the typical surface expression of large subglacial lakes, as well as eleven smaller areas over which ice-sheet surface elevations rapidly changed by discharge/filling of subglacial water. Here we present the first ice-penetrating radar evidence of subglacial conditions in this area. We identified a distinct ice-water interface only over a limited area within the boundaries of the investigated large smooth basins, previously hypothesized to be water-filled lakes. The radar characteristics in some areas are similar to those of a drained lake, indicating that parts of the bed are wet, but not a typical lake. We also find evidence for discrete water bodies outside of the lake boundaries. The lines of evidence indicate that the northern most two Recovery Lakes have recently drained.