Ongoing glacial isostatic contributions to observations of sea level change

Studies determining the contribution of water fluxes to sea level rise typically remove the ongoing effects of glacial isostatic adjustment (GIA). Unfortunately, use of inconsistent terminology between various disciplines has caused confusion as to how contributions from GIA should be removed from altimetry and GRACE measurements. In this paper, we review the physics of the GIA corrections applicable to these measurements and discuss the differing nomenclature between the GIA literature and other studies of sea level change. We then examine a range of estimates for the GIA contribution derived by varying the Earth and ice models employed in the prediction. We find, similar to early studies, that GIA produces a small (compared to the observed value) but systematic contribution to the altimetry estimates, with a maximum range of -0.15 to -0.5 mm yr-1. Moreover, we also find that the GIA contribution to the mass change measured by GRACE over the ocean is significant. In this regard, we demonstrate that confusion in nomenclature between the terms 'absolute sea level' and 'geoid' has led to an overestimation of this contribution in some previous studies. A component of this overestimation is the incorrect inclusion of the direct effect of the contemporaneous perturbations of the rotation vector, which leads to a factor of ˜two larger value of the degree two, order one spherical harmonic component of the model results. Aside from this confusion, uncertainties in Earth model structure and ice sheet history yield a spread of up to 1.4 mm yr-1 in the estimates of this contribution. However, even if the ice and Earth models were perfectly known, the processing techniques used in GRACE data analysis can introduce variations of up to 0.4 mm yr-1. Thus, we conclude that a single-valued 'GIA correction' is not appropriate for sea level studies based on gravity data; each study must estimate a bound on the GIA correction consistent with the adopted data-analysis scheme

[1]  W. Peltier,et al.  On postglacial geoid subsidence over the equatorial oceans , 1991 .

[2]  E. Leuliette,et al.  Closing the sea level rise budget with altimetry, Argo, and GRACE , 2009 .

[3]  M. Tamisiea,et al.  GRACE Gravity Data Constrain Ancient Ice Geometries and Continental Dynamics over Laurentia , 2007, Science.

[4]  W. Farrell.  Deformation of the Earth by surface loads , 1972 .

[5]  Archie Paulson,et al.  FAST TRACK PAPER: Inference of mantle viscosity from GRACE and relative sea level data , 2007 .

[6]  J. Willis,et al.  Assessing the globally averaged sea level budget on seasonal to interannual timescales , 2008 .

[7]  Guillaume Ramillien,et al.  Sea level budget over 2003-2008: A reevaluation from GRACE space gravimetry, satellite altimetry and Argo , 2009 .

[8]  Z. Martinec,et al.  Contribution of glacial-isostatic adjustment to the geocenter motion , 2011 .

[9]  A. Paulson,et al.  The rotational stability of an ice-age earth , 2005 .

[10]  J. Mitrovica,et al.  Glacial isostatic adjustment on a rotating earth , 2001 .

[11]  W. Peltier.  Chapter 4 Global glacial isostatic adjustment and modern instrumental records of relative sea level history , 2001 .

[12]  Donald F. Argus,et al.  Defining the translational velocity of the reference frame of Earth , 2007 .

[13]  F. Dahlen.  The Passive Influence of the Oceans upon the Rotation of the Earth , 1976 .

[14]  D. Chambers.  Calculating trends from GRACE in the presence of large changes in continental ice storage and ocean mass , 2009 .

[15]  W. Peltier,et al.  Ice Age Paleotopography , 1994, Science.

[16]  D. L. Anderson,et al.  Preliminary reference earth model , 1981 .

[17]  W. R. Peltier,et al.  Closure of the budget of global sea level rise over the GRACE era: the importance and magnitudes of the required corrections for global glacial isostatic adjustment , 2009 .

[18]  R. Steven Nerem,et al.  Ocean mass from GRACE and glacial isostatic adjustment , 2010 .

[19]  R. Nerem,et al.  Calibration of TOPEX/Poseidon and Jason Altimeter Data to Construct a Continuous Record of Mean Sea Level Change , 2004 .

[20]  W. Peltier.  GLOBAL GLACIAL ISOSTASY AND THE SURFACE OF THE ICE-AGE EARTH: The ICE-5G (VM2) Model and GRACE , 2004 .

[21]  W. Peltier,et al.  ICE-3G: A new global model of late Pleistocene deglaciation based upon geophysical predictions of po , 1991 .

[22]  On Postglacial Sea Level , 2007 .

[23]  F. Bryan,et al.  Time variability of the Earth's gravity field: Hydrological and oceanic effects and their possible detection using GRACE , 1998 .

[24]  I. Matsuyama,et al.  Rotational stability of dynamic planets with elastic lithospheres , 2006 .

[25]  J. Mitrovica,et al.  On post-glacial sea level – II. Numerical formulation and comparative results on spherically symmetric models , 2005 .