Investigating Ice-Mass Balance and Glacial Isostatic Adjustment in the Amundsen Sea Sector, West Antarctica, by Geodetic Observations and Modelling

• Applicant: Dr.-Ing. Mirko Scheinert
• Subject Area: Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography
• Term: from 2014 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 257472439

The West Antarctic Ice Sheet is responsible for the largest share of the Antarctic ice-mass loss, which is estimated to be on average in the order of 150 Gt/yr, the equivalent global sea-level rise of which would amount to about 0.4 mm/yr. A collapse of this marine-based ice sheet could raise global sea level far above predicted ranges during the 21st century. Besides the northern Antarctic Peninsula, the Amundsen Sea sector is the most sensitive region of change. In particular, the Amundsen Sea embayment, comprising the major ice streams of Pine Island Glacier, Thwaites Glacier and Smith Glacier, accounts for the major part of the mass loss. Hence, over the past years this region has developed into a hot spot area of interest for intensified investigation. To determine the ice-mass balance the proposed project utilizes the geodetic techniques of satellite gravimetry and satellite altimetry together with precise, repeated in-situ GPS measurements. However, the main source of uncertainty and, thus, by far the largest error component in satellite-gravimetric estimates of the ice-mass balance still originates from the glacial-isostatic adjustment (GIA) correction. This effect is in the same order of magnitude as the present-day ice-mass change itself. Besides their sophisticated modelling Antarctic GIA predictions still lack observational constraints and a sufficient complexity both of the ice-load history and of the Earth rheology. Therefore, we will start from a continent-wide consideration and will then focus our investigations on the Amundsen Sea sector, one of those regions showing the largest ice-mass loss and variability. We will utilize, firstly, a combination of satellite gravimetry and satellite altimetry to come up with an estimation of the GIA effect. This estimation will be validated by independent, ground-based GPS-derived vertical deformation data. For this, repeated GPS measurements will be carried out in the area of investigation, mainly during the cruise ANT-XXX/3 of the German R/V Polarstern. Secondly, the geodetic GIA estimates will be used as constraints for a refined GIA modelling. This regional model refinement will be based on the latest Antarctic-wide GIA model IJ05-R2 (Ivins et al., 2013) and allows to study variations in Earth rheology and ice-load history. For an improved regional GIA modelling also the results of investigations in geophysics, glacial morphology and geology shall be taken into consideration, which can especially help to better constrain the timing and position of the changing ice load. The regionally improved GIA model - incorporated into the superior Antarctic-wide GIA model - will be utilized to iteratively gain a better estimate of the ice-mass balance and the equivalent contribution to global sea-level change together with a throughout error assessment.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1158: Infrastructure area - Antarctic Research with Comparative Investigations in Arctic Sea Ice Areas
• International Connection: United Kingdom, USA
• Participating Persons: Professor Dr. Karsten Gohl; Dr. Erik Ivins; Dr. Joanne Johnson