Greenland uplift and regional sea level changes from ICESat observations and GIA modelling

Abstract

We study the implications of a recently published mass balance of the Greenland ice sheet (GrIS), derived from repeated surface elevation measurements from NASA’s ice cloud and land elevation satellite (ICESat) for the time period between 2003 and 2008. To characterize the effects of this new, high-resolution GrIS mass balance, we study the time-variations of various geophysical quantities in response to the current mass loss. They include vertical uplift and subsidence, geoid height variations, global patterns of sea level change (or fingerprints), and regional sea level variations along the coasts of Greenland. Long-wavelength uplifts and gravity variations in response to current or past ice thickness variations are obtained solving the sea level equation, which accounts for both the elastic and the viscoelastic components of deformation. To capture the short-wavelength components of vertical uplift in response to current ice mass loss, which is not resolved by satellite gravity observations, we have specifically developed a high-resolution regional elastic rebound (ER) model. The elastic component of vertical uplift is combined with estimates of the viscoelastic displacement fields associated with the process of glacial-isostatic adjustment (GIA), according to a set of published ice chronologies and associated mantle rheological profiles. We compare the sensitivity of global positioning system (GPS) observations along the coasts of Greenland to the ongoing ER and GIA. In notable contrast with past reports, we show that vertical velocities obtained by GPS data from five stations with sufficiently long records and from one tide gauge at the GrIS margins can be reconciled with model predictions based on the ICE-5G deglaciation model and the ER associated with the new ICESat-derived mass balance

Progress in modelling and observing Antarctic glacial isostatic adjustment

“…The exception was the Antarctic Peninsula, where rapid uplift was identified following the Larsen B Ice Shelf breakup and subsequent rapid glacier mass-loss into the oceans (Scambos et al 2004). There was suggestion that the rapid uplift may have been driven by elastic effects only, but subsequent elastic modelling that expanded the load change to higher spherical harmonic degree shows the elastic signal to be more spatially concentrated than that presented by Thomas et al (2011) (R Riva, personal communication, 2011Spada et al 2012). Very high GPS uplift rates have also been identified in the Amundsen Sea region (Groh et al 2012), and it is not yet clear if these are purely elastic or have a viscous component.…”

Towards Constraining Glacial Isostatic Adjustment in Greenland Using ICESat and GPS Observations

“…Here, we model the present day elastic movement in three overlapping time spans 2004-2007, 2005-2008, and 2006-2009, based on loading models derived from ICESat data (see Sect. 2.2), using the regional elastic rebound (RER) method (Spada et al 2012). The RER method follows the Green's functions methods (Farrell 1972), with load deformation coefficients (LDCs) based on an Earth model with PREM (Dziewonski and Anderson 1981) structure and given in the Earth's centre of mass reference frame.…”

“…It is therefore important to model the present day elastic response with high resolution and precision when GPS observations are used to constrain the GIA signal. Several studies have used GPS observations to constrain GIA models, in Antarctica (Bevis et al 2009; Thomas et al 2011), and in Greenland (Khan et al 2008;King et al 2010;Spada et al 2012). In these studies the elastic signal is subtracted from the GPS observations, to constrain the GIA signal hence relying on the accuracy of the elastic correction or its minor influence at the GPS stations.…”

Vertical and horizontal surface displacements near Jakobshavn Isbræ driven by melt‐induced and dynamic ice loss

“…Here, we account only for the horizontal displacement V(˛). An expression for the vertical displacement U(˛) is given by equation (4) in Spada et al [2012]. The vertical and horizontal displacements as a function of angular distance are displayed in Figure 3.…”

“…A previous study conducted by Khan et al [2010] used GPS measurements from 2006-2009 to study vertical crustal motion near JI. Other studies in Greenland have also used GPS measurements of vertical crustal displacements to study the present ice mass variability [Khan et al, 2007;Bevis et al, 2012;Nielsen et al, 2012] and to constrain the glacial isostatic adjustment (GIA) signal [Dietrich et al, 2005;Khan et al, 2008;King et al, 2010;Bevis et al, 2012;Spada et al, 2012]. Here, we expand the time series of Khan et al [2010] with an additional 3 years of data, and analyze both vertical and horizontal GPS displacements.…”