# Detection of Crustal Uplift Deformation in Response to Glacier Wastage in Southern Patagonia
## 5 Discussion  
The continuous SPI ice losses since the middle of the 20 th century have accelerated during the 21 st century, particularly with high frontal ablation experienced by freshwater calving glaciers. Although glacial retreat of the SPI is heterogeneous, the main contributor to the total mass losses is calving. Calving glaciers represent 91% of Patagonian Icefields [14]. The spatial pattern of the SPI ice elevation change is complex and non-uniform comparing different basins [11]. Studies by [PERSON] et al. [57] using geodetic data suggest that the El Nino-Southern Oscillation (ENSO) 2015-2016 had a major impact on SPI ice mass changes that has continued through 2018. In this sense, the results we have achieved in the period 2000-2019, both in the plateau (accumulation) and in the frontal ablation zone of the SPI eastern slope, are coincident with those reported by [PERSON] et al. [14]. From the analysis of ICESat-1, we estimated a maximum \(\Delta\)_lt_ rate of \(-\)2.58 \(\pm\) 0.26 m a\({}^{-1}\) for the period 2000-2006 for the high plateau of the Upsala glacier. However, the highest thinning rate was found at the ablation zone of the Upsala glacier, yielding \(-\)5.49 \(\pm\) 0.14 m a\({}^{-1}\) in the 2000-2007 period. By using ICESat-2, the value reached \(-\)3.36 \(\pm\) 0.01 m a\({}^{-1}\) for the 2000-2019 period. Despite the difference in time intervals, our results are similar to those reported by [PERSON] et al. [58], [PERSON] et al. [11], and [PERSON] et al. [14], showing that a significant retreat and mass losses have taken place in the SPI glaciers during the last decade. On the other hand, our results are higher than those estimated by [PERSON] et al. [13] who estimated the geodetic mass balance of the Santa Cruz River basin 1979-2018 period, where the Upsala and Viedma glaciers reached maximum rates of \(-\)2.16 \(\pm\) 0.11 m a\({}^{-1}\) and \(-\)1.59 \(\pm\) 0.11 m a\({}^{-1}\), respectively. The discrepancy could be  
Figure 8: Elevation changes for O Higgins, Chico, Viedma, and Upsala glaciers in the 2000–2019 period. attributed firstly to the longer time span and, secondly, because they used optical sensors (Hexagon KH-9 and ASTER) for the estimation of elevation changes. The four most important glaciers on the eastern and northern side of the SPI (O'Higgins, Chico, Viedma, and Upsala) are shrinking rapidly. Our results show negative exposed trends are intensified in areas below the ELA (1300 m a.s.l. ), and the ice elevation has changed by more than 100 m in almost two decades (Figure 8). During the period 2000-2015/16, these four glaciers have recorded thinning rates of up to 2 ma\({}^{-1}\) in the accumulation zones, while in the tongues, the Chico reaches up to \(-6\) m a\({}^{-1}\) and Viedma up to \(-4\) m a\({}^{-1}\)[58]. [PERSON] et al. [11], found a high surface elevation loss rate in the ablation areas (lower terminus) of the Upsala and Viedma glaciers in the summer of 2011/2012. Instead, the Viedma glacier has suffered an alarming retreat since 2015, with mean velocities at its terminus of 3.5 m d\({}^{-1}\) between April 2014 and April 2016 [59]. In the last seven years, it has lost an area of 2.5 km\({}^{2}\) in the frontal zone, equivalent to what it had previously lost in 50 years. Consequently, the acceleration in ice loss would produce an unequivocal acceleration in the elastic response of the Earth. The volumetric decrease in SPI ice masses in the last 150 years could be linked to the Earth's crustal uplift [24]. Geodetic studies to detect the crustal deformation have been carried out in the SPI region. [PERSON] et al. [25] found that in the area near the SPI plateau, the uplift displacement was 39 mm a\({}^{-1}\) during the period 2003-2006. Considering a longer time (1999-2014), [PERSON] et al. [19] and [PERSON] et al. [26] observed crustal uplift in the Nunatak Viedma and Cerro Gorra Blanca of 31 and 41 mm a\({}^{-1}\), respectively. It should be noted that the Model B of vertical crustal motion prediction proposed by [PERSON] et al.