Glacial-isostatic adjustment in the Southern Patagonia Icefield based upon permanent GNSS stations

The Southern Patagonia Icefield (SPI) is the largest continuous ice mass in Southern Hemisphere outside Antarctica. It has been shrinking since the little Ice Age (LIA) period with increasing rates in recent years. In response to this deglaciation process an uplift crustal deformation has been expected. In order to test this hypothesis, a number of GNSS stations installed at both side of the international border between Chile and Argentina, have been repeatedly measured in recent decades yielding vertical velocities up to 41 mm/a.     The obtained horizontal velocities have also shown that GIA is only one of the main components been the tectonic deformations the other factors, including the western interseismic tectonic deformation field related to plate subduction (Richter et al., 2016).

We addressed this hypothesis by installing two permanent GNSS stations in nunataks located in the northern half of the SPI. The first one called ECRG was setup up within the accumulation area at 1417 m asl and was measuring with several interruptions due to power supply between 2015/10/24 and 2018/06/18, yielding a total of 371 days with data. The second station called ECGB was installed at 1610 m asl in 2015/10/08 and was continuously measuring also with interruptions until 2019/05/28, with a total of 542 measured days. The stations were equipped with a Trimble NetR9 receiver and a Trimble Zephyr (TRM41249.00) antennae without protective radomes. The collected data was processed with the Bernese v5.0 software and the data were linked to the International GNSS Service 2008 (IGS08) permanent stations.

The preliminary results indicate vertical velocities of 33.03 ±2.14 mm/a at ECRG and 36.55±2.58 mm/a at ECGB. The mean horizontal velocities reached 11.7 mm/a with an azimuth of 43º. These results are within the maximum values obtained in previous studies that measured nearby stations for short periods of time in several occasions. The high vertical velocities and their spatial distribution are a clear indication of the GIA response of this part of Southern Patagonia.

Reference

Richter, A., Ivins, E., Lange, H., Mendoza, L., Schröder, L., Hormaechea, J. L., … Dietrich, R. (2016). Crustal deformation across the Southern Patagonian Icefield observed by GNSS. Earth and Planetary Science Letters, 452, 206–215. https://doi.org/10.1016/j.epsl.2016.07.042