01831nas a2200157 4500008004100000245009400041210006900135260001200204300001200216490000700228520126700235100001501502700002401517700001401541856011801555 2014 eng d00aNear-Surface Internal Melting - a Substantial Mass Loss on Antarctic Dry Valley Glaciers.0 aNearSurface Internal Melting a Substantial Mass Loss on Antarcti c04/2014 a361-3740 v603 aThe McMurdo Dry Valleys, southern Victoria Land, East Antarctica, are a polar desert, and melt from glacial ice is the primary source of water to streams, lakes and associated ecosystems. Previous work found that to adequately model glacier ablation and subsurface ice temperatures with a surface energy-balance model required including the transmission of solar radiation into the ice. Here we investigate the contribution of subsurface melt to the mass balance of (and runoff from) Dry Valley glaciers by including a drainage process in the model and applying the model to three glacier sites using 13years of hourly meteorological data. Model results for the smooth glacier surfaces common to many glaciers in the Dry Valleys showed that sublimation was typically the largest component of surface lowering, with rare episodes of surface melting, consistent with anecdotal field observations. Results also showed extensive internal melting 5-15 cm below the ice surface, the drainage of which accounted for 50% of summer ablation. This is consistent with field observations of subsurface streams and formation of a weathering crust. We identify an annual cycle of weathering crust formation in summer and its removal during the 10 months of winter sublimation.1 aHoffman, M1 aFountain, Andrew, G1 aListon, G uhttps://mcm.lternet.edu/content/near-surface-internal-melting-substantial-mass-loss-antarctic-dry-valley-glaciers02772nas a2200169 4500008004100000245009200041210006900133260001200202490000800214520222300222100002302445700001502468700001502483700002402498700001502522856006502537 2012 eng d00aSeismic multiplet response triggered by melt at Blood Falls, Taylor Glacier, Antarctica0 aSeismic multiplet response triggered by melt at Blood Falls Tayl c07/20120 v1173 a

Meltwater input often triggers a seismic response from glaciers and ice sheets. It is difficult, however, to measure melt production on glaciers directly, while subglacial water storage is not directly observable. Therefore, we document temporal changes in seismicity from a dry-based polar glacier (Taylor Glacier, Antarctica) during a melt season using a synthesis of seismic observation and melt modeling. We record icequakes using a dense six-receiver network of three-component geophones and compare this with melt input generated from a calibrated surface energy balance model. In the absence of modeled surface melt, we find that seismicity is well-described by a diurnal signal composed of microseismic events in lake and glacial ice. During melt events, the diurnal signal is suppressed and seismicity is instead characterized by large glacial icequakes. We perform network-based correlation and clustering analyses of seismic record sections and determine that 18% of melt-season icequakes are repetitive (multiplets). The epicentral locations for these multiplets suggest that they are triggered by meltwater produced near a brine seep known as Blood Falls. Our observations of the correspondingp-wave first motions are consistent with volumetric source mechanisms. We suggest that surface melt enables a persistent pathway through this cold ice to an englacial fracture system that is responsible for brine release episodes from the Blood Falls seep. The scalar moments for these events suggest that the volumetric increase at the source region can be explained by melt input.

1 aCarmichael, J., D.1 aPettit, E.1 aHoffman, M1 aFountain, Andrew, G1 aHallet, B. uhttp://onlinelibrary.wiley.com/doi/10.1029/2011JF002221/full00519nas a2200121 4500008004100000245009200041210006900133260004900202300000800251490001000259100001500269856011300284 2011 eng d00aSpatial and Temporal Variability of Glacier Melt in the McMurdo Dry Valleys, Antarctica0 aSpatial and Temporal Variability of Glacier Melt in the McMurdo  aPortlandbPortland State Universityc01/2011 a2960 vPh.D.1 aHoffman, M uhttps://mcm.lternet.edu/content/spatial-and-temporal-variability-glacier-melt-mcmurdo-dry-valleys-antarctica00503nas a2200121 4500008004100000245009100041210006900132490000800201100001500209700002400224700001400248856011900262 2008 eng d00aSurface energy balance and melt thresholds over 11 years at Taylor Glacier, Antarctica0 aSurface energy balance and melt thresholds over 11 years at Tayl0 v1131 aHoffman, M1 aFountain, Andrew, G1 aListon, G uhttps://mcm.lternet.edu/content/surface-energy-balance-and-melt-thresholds-over-11-years-taylor-glacier-antarctica