# Elevation and Mass Changes of the Southern Patagonia Icefield Derived from TanDEM-X and SRTM Data
## 5 Conclusions  
Our results confirm the large mass loss from the Southern Patagonian Icefield. Our estimates are slightly smaller than given in several previous studies. This might be attributed to the fact that in recent years the orographically-driven precipitation due to enhanced westerly flow has also increased [1]. We cannot observe an increase in mass loss rates compared to earlier studies since the 1970s, however we confirm the increase by one magnitude of mass loss since the Little Ice Age. We provide a lower bound estimate, since we did not consider volume and mass changes resulting from the subaqueous loss of retreating tidewater and freshwater calving glaciers. Due to the lack of respective information \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Area** (**km2\({}^{\circ}\)**)} & **Volume** & **Mass** & \multicolumn{2}{c}{**Spec. Mass**} & \multirow{2}{*}{**Region**} & \multirow{2}{*}{**Method/Data**} & \multirow{2}{*}{**Reference**} \\  & **(km2\({}^{\circ}\))** & & & & & & \\  & **(km3\(\cdot\)a\({}^{-1}\))** & & & & & & \\  & & & & & & & \\ \hline  & \(-1.39\pm 0.28\) & & & SPI & 1650–2000 & dh/dt reconstruction & [39] \\
13.000 & \(-13.5\pm 0.8\) & \(-15.2\pm 0.72\) & \(-0.934\) & SPI & 1968/75–2000 & dh/dt, maps-SRTM & [61] \\
13.000 & \(-38.7\pm 4.4\) & & \(-2.679\) & SPI & 1995–2000 & dh/dt maps SRTM & [8] \\
12.118 & \(-22.2\pm 1.3\) & \(-20.0\pm 1.2\) & \(-1.476\) & SPI & 2000–2011 & dh/dt ASTER-SRTM & [7] \\
12.880 & \(-14.59\pm 0.37\) & \(-13.14\pm 0.42\) & \(-1.019\) & SPI & 2000–2011/12 & dh/dt/dt TX-SRTM & [40] \\
10.772 & \(-11.5\pm 2.3\) & \(-10.39\pm 2.2\) & \(-0.954\) & SPI & 2000–2015/16 & dh/dt TDX-SRTM & this study \\
12.573 & \(-13.2\pm 3.6\) & \(-11.84\pm 2.2\) & \(-0.941\) & SPI & 2000–2015/16 & dh/dt TDX-SRTM & this study \\  & & \(-29\pm 10\) & & Southern Andes & 203–209 & Gravimetry/GRACE & [62,63] \\  & & \(-23.0\pm 3.0\) & & Fuego-Patagonia & 2003–2011 & Gravimetry/GRACE & [64] \\  & \(-27.9\pm 11\) & & \(-1.6\) & & Patagonia & 04/200–212/12/200 & Gravimetry/GRACE & [65] \\  & \(-0.79\pm 0.16\) & \(-0.65\) & & & NPI & 1870–2000 & dh/dt reconstruction & [39] \\  & \(-32\pm 0.4\) & & & NPI & 1968/75–2000 & dh/dt, maps-SRTM & [8] \\  & \(-40.6\pm 0.11\) & \(-3.96\pm 0.14\) & & NPI & 2000–2011 & dh/dt ASTER-SRTM & [66] \\  & \(-4.4\pm 0.13\) & \(-3.96\pm 0.14\) & & NPI & 2000–2014 & dh/dt TDX-SRTM & [40] \\  & & & & Corollifera & 2000–2011 & dh/dt ASTER-SRTM & [67] \\  & & & Darwin & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Overview of elevation and mass change estimates for the SPI compiled from different studies. Grey background indicates values of this study. The 10.772 km\({}^{2}\) refer to actually measured area while 12.573 km\({}^{2}\) correspond to the value extrapolated to data gaps as described in method section. on ice thickness in those areas estimates would be hardly reliable. We also provide computations for different density scenarios for volume-mass conversion in order to enable direct comparison with previous studies. The spatially detailed analysis shows a very heterogeneous pattern of glacier elevation changes. While some glaciers such as Jorge Montt, Upsala or HPS12 show very high lowering rates mainly driven by dynamic adjustment to the new glacier front position after fast retreat, other major glaciers such as Perito Moreno or Europa have remained roughly balanced. Our analysis is in line with a previous study considering hypsometry as a major factor to explain the sensitivity of SPI glaciers to change in equilibrium line altitude. Pio XI still shows a positive mass balance with a thickening of the glacier tongue by several meters per year on average. Our observations do not reveal indications for a surge-type behavior of this glacier, but rather support an explanation of continuous mass gain in conjunction with the specific glacier geometry. This illustrates that various factors have to be taken into account to explain the impact and reaction of glaciers of the SPI.