Abstract

Thirtyone GPS geodetic measurements of crustal uplift in southernmost South America determined extraordinarily high trend rates (> 35 mm/yr) in the northcentral 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 endmember models provide good fits: both require a lithospheric thickness of 36.55.3 km. However, one endmember has a mantle viscosity near =1.6 x10(18)Pas 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 endmember has much larger viscosity: = 8.0 x10(18)Pas, half the post-LIA collapse rate, and a steadily rising loss rate in the twentiethcentury after AD 1943, reaching -25.9 Gt/yr during 1995-2012. Key Points Post-Little Ice Age load changes cause viscoelastic GIA response GPS results improve knowledge of ice load history since LIA and Earth model Gravity changes from the load changes and GIA influence interpretations of GRACE