Data_Sheet_1_Assessing Snow Accumulation Patterns and Changes on the Patagonian Icefields.docx

Recent evidence shows that most 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 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) in addition to 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.

近期研究表明，多数巴塔哥尼亚冰川正在迅速退缩。由于缺乏该区域长期现场气象观测数据，对冰川如何响应气候变化的理解极为有限，且冰川表面质量平衡模型参数化存在不确定性，这阻碍了对冰川对当前及预测气候变化的稳健评估。一个核心关注点是准确估算降水相。在本研究中，我们对北巴塔哥尼亚冰原（NPI）和南巴塔哥尼亚冰原（SPI）的雪积累的空间和时间模式进行了评估。我们使用了区域气候模型RegCM4.6和四种相分离方法（PPM），并结合使用超声波深度计（UDG）进行的短期雪积累观测。雪积累结果显示，与东侧相比，两座冰原的西侧雪积累率更高。这些数值取决于所采用的PPM，平均差异达到1,500毫米水当量，某些地区的差异甚至超过3,500毫米水当量。这些差异可能导致基于不同雪积累定义方案的冰川质量平衡估算出现分歧。在比较SPI高原地区的UDG观测数据与模式数据时，发现短期内的良好一致性；然而，本研究中确定的雪积累率与使用冰芯数据进行的年度尺度先前估计之间存在重要差异。在SPI西侧的秋季，主要存在显著的上升趋势，而在东侧，秋季观察到显著的下降趋势。总体而言，对于其他地区和其他季节，无法确定显著变化。此外，由先前工作确定的具有积极且稳定的海拔和前沿变化的冰川与2000-2015年期间雪积累增加的区域相关。这表明，雪积累的增加正在减弱某些巴塔哥尼亚冰川在整体冰川退缩区域对升温的响应。