ALBERT

Description: Albedo is one of the parameters that govern energy availability for snow and ice surface ablation, and subsequently the surface mass balance conditions of temperate glaciers and ice caps (GIC). Here, we document snow and ice albedo changes for Mittivakkat Gletscher (MG) in Southeast Greenland (2000–2013), for which an 18-year record of direct surface mass balance measurements exists. The MODerate Imaging Spectroradiometer (MODIS MCD43A3) albedo product was used to study MG's snow and ice albedo, evaluated against supraglacial automatic weather station (AWS) observations. In general, by the end of the mass balance year (EBY), MG's AWS observed bare ice albedo reached ∼ 0.3 only just exceeding values observed for proglacial bedrock ( ∼ 0.2). The analysis reveals negative mean trends in the MODIS-derived MG EBY albedo for the period 2000–2013 with a significant decline in mean glacier-wide albedo of 0.10. The greatest decline in albedo, of 0.25, occurred near the equilibrium line altitude (ELA), an important surface cover and albedo transitional zone. The EBY albedo correlates significantly with ELA and net winter and summer glacier mass balance records.

Description: ABSTRACT Glacier surface mass balance (SMB) observations for the Andes Cordillera are limited and therefore estimates of the SMB contribution to sea-level rise are highly uncertain. Here (in Part 3), we simulate glacier surface meteorological and hydrological conditions and trends for the Andes Cordillera (1979/80–2013/14; 35 years), covering the tropical latitudes in the north down to the sub-polar latitudes in the far south, including the Northern Patagonia Icefield (NPI) and Southern Patagonia Icefield (SPI). Surface meteorological conditions and heat- and mass-transfer processes were simulated for all glaciers having an area equal to or greater than 0.5 km 2 . SnowModel – a fully integrated energy balance, blowing-snow distribution, multi-layer snowpack, and runoff routing model – was used to simulate glacier SMBs for the Andes Cordillera. The Randolph Glacier Inventory (RGI; v. 4.0) and NASA Modern-Era Retrospective Analysis for Research and Applications (MERRA) products, downscaled in SnowModel, allowed us to conduct relatively high-resolution (1-km horizontal grid; 3-h time step) simulations of glacier air temperature, precipitation, sublimation, evaporation, runoff, and SMB. These simulated glacier SMBs were verified against both independent direct observed annual glacier SMB and satellite gravimetry and altimetry derived SMB, indicating a good agreement. For Andes glaciers, the 35-year mean annual SMB was found to be −1.13 m water equivalent (w.e.), while the cumulative SMB was −39.6 m w.e., which is equal to a cumulative SMB contribution of 3.4 mm sea-level equivalent (SLE) (∼0.1 mm SLE per year). However, for both NPI and SPI, the mean SMB was positive (where likely calving explains why geodetic estimates are negative). For the Andes Cordillera, the simulated mean glacier-specific runoff was 41 L s −1 km −2 , while for NPI and SPI it was 213 and 198 L s −1 km −2 , respectively, indicating available water resources from NPI and SPI.