Abstract
ABSTRACTTropical glaciers constitute an important source of water for downstream populations. However, our understanding of glacial melt processes is still limited. One observed process that has not yet been quantified for tropical glaciers is the enhanced melt caused by the longwave emission transfer. Here, we use high-resolution surface temperatures obtained from the thermal infrared imagery of the Cuchillacocha Glacier, in the Cordillera Blanca, Peru in June 2014 to calculate a margin longwave flux. This longwave flux, reaching the glacier margin from the adjacent exposed rock, varies between 81 and 120 W m−2 daily. This flux is incorporated into a physically-based melt model to assess the net radiation budget at the modeled glacier margin. The simulation results show an increase in the energy available for melt by an average of 106 W m−2 during the day when compared with the simulation where the LWmargin flux is not accounted for. This value represents an increase in ablation of ~1.7 m at the glacier margin for the duration of the dry season. This study suggests that including the quantification of the glacier margin longwave flux in physically-based melt models results in an improved assessment of tropical glacier energy budget and meltwater generation.
Highlights
Glacier meltwater provides water resources for some of the most populated regions on Earth (Barnett and others, 2005)
The margin longwave flux obtained from the infrared images shows a strong daily cyclicity (Fig. 5) over the 33 h of available thermal infrared imagery
We used ground-based thermal infrared imagery to obtain a margin longwave radiation flux, emitted from the terrain surrounding the glacier. This flux varies between 80 and 120 W m−2 diurnally and is more dependent on local shading than on elevation. We include this margin longwave flux in a physically-based melt model of the glacier to investigate the impact on local ablation and energy balance at the glacier margin
Summary
Glacier meltwater provides water resources for some of the most populated regions on Earth (Barnett and others, 2005). In the last 20 years, glaciers located in the tropics have gained interest and have been studied at a few well instrumented sites, such as the Zongo Glacier, Bolivia (Wagnon and others, 1999a, b; Sicart and others, 2011), the Antisana Glacier, Ecuador (Francou and others, 2004, Favier and others, 2004a, b), Kilimanjaro in Tanzania, (Mölg and Hardy, 2004; Mölg and others, 2008), the Lewis Glacier in Kenya (Nicholson and others, 2010, 2013) and Artesonraju and Shallap in Peru (Kaser and Osmaston, 2002; Winkler and others, 2009; Gurgiser and others, 2013a, b). These studies have shown some of the distinct characteristics of the energy balance of tropical glaciers, such as the importance of negative latent heat fluxes on the energy balance during the dry season (Wagnon and others, 1999b)
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