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Distributed ice thickness and glacier volume in southern South America

Carrivick, Jonathan L., Davies, Bethan J., James, William H.M., Quincey, Duncan J., Glasser, Neil F.
Global and planetary change 2016 v.146 pp. 122-132
glaciers, ice, models, rivers, sea level, snowmelt, topography, watersheds, Argentina
South American glaciers, including those in Patagonia, presently contribute the largest amount of meltwater to sea level rise per unit glacier area in the world. Yet understanding of the mechanisms behind the associated glacier mass balance changes remains unquantified partly because models are hindered by a lack of knowledge of subglacial topography. This study applied a perfect-plasticity model along glacier centre-lines to derive a first-order estimate of ice thickness and then interpolated these thickness estimates across glacier areas. This produced the first complete coverage of distributed ice thickness, bed topography and volume for 617 glaciers between 41°S and 55°S and in 24 major glacier regions. Maximum modelled ice thicknesses reach 1631m±179m in the South Patagonian Icefield (SPI), 1315m±145m in the North Patagonian Icefield (NPI) and 936m±103m in Cordillera Darwin. The total modelled volume of ice is 1234.6km³±246.8km³ for the NPI, 4326.6km³±865.2km³ for the SPI and 151.9km³±30.38km³ for Cordillera Darwin. The total volume was modelled to be 5955km³±1191km³, which equates to 5458.3Gt±1091.6Gt ice and to 15.08mm±3.01mm sea level equivalent (SLE). However, a total area of 655km² contains ice below sea level and there are 282 individual overdeepenings with a mean depth of 38m and a total volume if filled with water to the brim of 102km³. Adjusting the potential SLE for the ice volume below sea level and for the maximum potential storage of meltwater in these overdeepenings produces a maximum potential sea level rise (SLR) of 14.71mm±2.94mm. We provide a calculation of the present ice volume per major river catchment and we discuss likely changes to southern South America glaciers in the future. The ice thickness and subglacial topography modelled by this study will facilitate future studies of ice dynamics and glacier isostatic adjustment, and will be important for projecting water resources and glacier hazards.