Abstract
Recent evidence shows that most of Patagonian glaciers are receding rapidly. Due to the lack of in-situ long-term meteorological observations, the understanding of how glaciers are responding to changes in climate over this region is extremely limited and high uncertainties exist in the glacier surface mass balance model parameterizations. This precludes a robust assessment of glacier response to current and projected climate change. An issue of central concern is the accurate estimation of precipitation phase. In this work, we have assessed spatial and temporal patterns in snow accumulation in both the North Patagonia Icefield (NPI) and South Patagonia Icefield (SPI). We used a regional climate model, RegCM4.6 and four Phase Partitioning Methods (PPM) and short-term snow accumulation observations using ultrasonic depth gauges (UDG). Snow accumulation shows that rates are higher on the west side relative to the east side for both Icefields. The values depend on the PPM used and reach a mean difference of 1,500 mm w.e. with some areas reaching differences higher than 3,500 mm w.e. These differences could lead to divergent mass balance estimations, depending on the scheme used to define the snow accumulation. Good agreement is found in comparing UDG observations with modeled data on the plateau area of the SPI during a short time period, however, there are important differences between rates of snow accumulation determined in this work and previous estimations using ice core data at annual scale. Significant positive trends are mainly present in the autumn season on the west side of the SPI, while on the east side, significant negative trends in autumn were observed. Overall, for the rest of the area and during other seasons, no significant changes can be determined. In addition, glaciers with positive and stable elevation and frontal changes determined by previous works, are related to areas where snow accumulation has increased during the period 2000-2015. This suggests that increases in snow accumulation are attenuating the response of some Patagonian glaciers to warming in a regional context of overall glacier retreat.
Highlights
Patagonia is the largest glaciated area in the Southern Hemisphere outside Antarctica
The spatial patterns in the distribution of annual snow accumulation are similar between the four Phase Partitioning Methods (PPM) methods (Figure 2)
All PPM methods driven by the data from RegCM4.6 show that the west sides of both Patagonian Icefields receive a higher amount of snowfall relative to the east side, indicating the capability of RegCM4.6 to capture the extreme orographic effect (Table 2 and Figure 2)
Summary
Patagonia is the largest glaciated area in the Southern Hemisphere outside Antarctica. Previous studies have focused on comparing surface elevation changes during recent decades derived from digital elevations model (DEMs) obtained from topographic and satellite data in both the North Patagonia Icefield (NPI) and the South Patagonia Icefield (SPI). Overall, these analyses show surface lowering in almost all the NPI, with some exceptions in the accumulation zones (Rivera et al, 2007; Dussaillant et al, 2018; Foresta et al, 2018). Due to the lack of observationbased analyses, high uncertainties exist in the glacier surface mass balance model parameterizations precluding a complete validation of the simulated accumulation (Villarroel et al, 2013) as well as a robust assessment of the response of the glaciers to projected climate change
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