Observed crustal uplift near the Southern Patagonian Icefield constrains improved viscoelastic Earth models

摘要

Thirty-one GPS geodetic measurements of crustal uplift in southernmost South America determined extraordinarily high trend rates (> 35 mm/yr) in the north-central part of the Southern Patagonian Icefield. These trends have a coherent pattern, motivating a refined viscoelastic glacial isostatic adjustment model to explain the observations. Two end-member models provide good fits: both require a lithospheric thickness of 36.5 ± 5.3 km. However, one end-member has a mantle viscosity near η =1.6 ×10~(18) Pa s and an ice collapse rate from the Little Ice Age (LIA) maximum comparable to a lowest recent estimate of 1995-2012 ice loss at about ?11 Gt/yr. In contrast, the other end-member has much larger viscosity: η = 8.0 ×10~(18) Pa s, half the post-LIA collapse rate, and a steadily rising loss rate in the twentieth century after AD 1943, reaching ?25.9 Gt/yr during 1995-2012.