Description
The Greenland Ice Sheet (GrIS) is currently undergoing substantial mass loss, with major
consequences for both the Earth system and human societies, including a significant
contribution to the ongoing acceleration of global mean sea level rise. Accurately
estimating the GrIS mass balance therefore represents a major focus of current research.
However, it remains challenging and, to date, still imprecise.
One of the main reasons is Glacial Isostatic Adjustment (GIA) - the viscoelastic response
of the solid Earth to the growth and decay of ice sheets at its surface. Because geodetic
observations are among the most used tools to quantify ice mass changes, robust
estimates of GIA corrections are essential for the accurate interpretation of these
measurements.
This study focuses on deformations induced by ice mass loss since the Little Ice Age (LIA)
and their impact on present-day vertical land motion inferred from GNSS observations.
Using a reconstructed history of the GrIS and its peripheral glaciers, we model LIA-driven
viscoelastic deformations assuming different Earth models, exploring a range of values
for two rheological parameters: the lithosphere thickness and the upper mantle viscosity.
These simulations, combined with corrections for GIA associated with the last glacial
maximum and the elastic response to contemporary ice melting, are compared against
GNSS observations. Our results explain the uplift rates at most of the GNSS stations and
are consistent with existing literature, with LIA-induced vertical land motion best
accounted for by a 160 km thick lithosphere and an upper mantle viscosity of 2.73 × 10¹⁹
Pa·s.
As we explore the rheological structure beneath Greenland, we pay particular attention
to the southeastern region, where uplift rates are unusually high. Southeastern Greenland
exhibits significant lateral variations in mantle viscosity and lithospheric thickness, likely
related to the track of soft material left by the Iceland hotspot. Our simulations support
the presence of a low viscosity/thin lithosphere zone in this region, and we further
investigate its effects by adding to our modeling an asthenospheric layer within the upper
mantle.
Overall, this study demonstrates that deformations induced by the LIA constitute a non-
negligible contribution to present-day geodetic signals. Accounting for this component is
therefore essential to reduce uncertainties in ice mass balance estimates and to better
understand Greenland’s contribution to global sea level rise.