Vertical acceleration of Icelandic crust measured by continuous GPS geodesy

We present current vertical crustal velocity and acceleration fields for Iceland as measured by 62 continuously operating GPS stations. After analyzing available CGPS data from 1995 to present and manually repairing breaks and removing transient earthquake and volcanic deformation signals, we calculate velocities and accelerations by fitting a second order polynomial model consisting of a coordinate offset term and two additional terms representing the time-averaged coordinate velocity and acceleration. Our velocity estimates agree closely with previously published velocity fields and show a broad region of rapid uplift in central Iceland, with near zero uplift observed near coastal regions. The largest vertical velocities occur near the center of the island, between the Vatnajökull and Hofsjökull ice sheets at rates exceeding 20 mm/yr. Velocity uncertainties have a mean of ~0.1mm/yr. The pattern of acceleration mimics that of the velocity field such that the velocity contrast between the interior and coastal regions is being enhanced. Largest positive accelerations of ~1.5 mm/yr² are observed in central Iceland and acceleration uncertainties have a mean of ~0.2mm/yr². Previous studies have modeled rapid uplift in Iceland as an isostatic response to loss of ice mass from the central Iceland ice sheets. We propose that the accelerating uplift is a result of accelerating ice mass loss, with possible implications for climate driven glacial retreat and models for ice loss and isostatic adjustment.