Glacial Isostatic Adjustment in Antarctica : a rheological study

Alexandre Boughanemi,Anthony Mémin

doi:10.5194/egusphere-egu22-7906

Abstract

&lt;p&gt;&amp;#160;The Antarctic Ice Sheet (AIS) is the largest ice sheet on Earth that has known important mass&amp;#160;&lt;br&gt;&amp;#160;changes during the last 20 kyrs. These changes deform the Earth and modify its gravity field,&amp;#160;&lt;br&gt;&amp;#160;a process known as Glacial Isostatic Adjustment (GIA). GIA is directly influenced by the mechanical&lt;br&gt;&amp;#160;properties and internal structure of the Earth, and is monitored using Global Navigation Satellite&amp;#160;&lt;br&gt;&amp;#160;System positioning or gravity measurements. However, GIA in Antarctica remains poorly constrained &amp;#160;&lt;br&gt;&amp;#160;due to the cumulative effect of past and present ice-mass changes, the unknown history of the past&lt;br&gt;&amp;#160;ice-mass change, and the uncertainties of the mechanical properties of the Earth. The viscous&amp;#160;&lt;br&gt;&amp;#160;deformation due to GIA is usually modeled using a Maxwell rheology. However, other geophysical&lt;br&gt;&amp;#160;processes employ Andrade (tidal deformation) or Burgers (post-seismic deformation) laws that could&amp;#160;&lt;br&gt;&amp;#160;result in a more rapid response of the Earth. We investigate the effect of using these&lt;br&gt;&amp;#160;different rheology laws to model GIA-induced deformation in Antarctica. &amp;#160;&lt;/p&gt;&lt;p&gt;Employing the ALMA and TABOO softwares, we use the Love number and Green functions formalism to &lt;br&gt;compute the surface motion and the gravity changes induced by the past and present ice-mass redistributions. &lt;br&gt;We use the elastic properties and the radial structure of the preliminary reference Earth model (PREM) and the &lt;br&gt;viscosity profile given by Hanyk (1999). The deformation is computed for the three rheological laws mentioned &lt;br&gt;above using ICE-6G and elevation changes from ENVISAT (2002-2010) to represent the past and present changes&lt;br&gt;of the AIS, respectively.&amp;#160;&lt;/p&gt;&lt;p&gt;We obtain that the three rheological laws lead to significant Earth response within a 20 kyrs time interval since &lt;br&gt;the beginning of the ice-mass change. The differences are the largest between Maxwell and Burgers rheologies &lt;br&gt;during the 500 years following the beginning of the surface-mass change. Regarding the response to present &lt;br&gt;changes in Antarctica, the largest discrepancies are obtained in regions with the greatest current melting rates, &lt;br&gt;namely Thwaites and Pine Island Glacier in West Antarctica. Uplift rates computed twelve years after the end of&lt;br&gt;the present melting using Burgers and Andrade rheologies are five and two times larger than those obtained &lt;br&gt;using Maxwell, respectively.&amp;#160;&lt;/p&gt;

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