The surface energy fluxes of glaciers determine surface melt and their adequate parameterization is one of the keys for a successful prediction of future glacier mass balance and freshwater discharge. Chile hosts glaciers in a large range of latitudes under contrasting climatic settings: from 18° S in the Atacama Desert to 55° S on Tierra del Fuego Island. We found the Patagonian glaciers to experience higher surface melt rates as compared to the glaciers of the Central Andes due to a higher contribution of the turbulent flux of sensible heat, less negative longwave radiation balance and a positive contribution of the turbulent flux of latent heat. Glaciers in the Central Andes melt at higher rates at cloud-free conditions whilst glaciers in Patagonia melt faster on cloudy days. The models underestimated the measured emissivity of the clearsky atmosphere in the Wet Andes. The different parameterizations of the turbulent fluxes of sensible and latent heat show similar variability but different absolute values due to different parameterizations of the transport coefficients and stability corrections. We conclude that when working towards physical melt models it is not sufficient to use the observed melt as a measure of model performance: the model parameterizations of individual components of the energy balance have to be validated individually against measurements.
Schaefer, M., Fonseca, D., Farias-Barahona, D., and Casassa, G.: Surface energy fluxes on Chilean glaciers: measurements and models, The Cryosphere Discuss., https://doi.org/10.5194/tc-2019-51, in review, 2019.
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.
Bravo, C., Bozkurt, D., Gonzalez-Reyes, A., Quincey, D., Ross, A., Farías-Barahona, D., Rojas, M. „Assessing snow accumulation patterns and changes on the Patagonian Icefields“. Frontiers in Environmental Science 7:30, doi: 10.3389/fenvs.2019.00030
The Echaurren Norte Glacier is a reference glacier for the World Glacier Monitoring Service (WGMS) network and has the longest time series of glacier mass balance data in the Southern Hemisphere. The data has been obtained by the direct glaciological method since 1975. In this study, we calculated glacier area changes using satellite images and historical aerial photographs, as well as geodetic mass balances for different periods between 1955 and 2015 for the Echaurren Norte Glacier in the Central Andes of Chile. Over this period, this glacier lost 65% of its original area and disaggregated into two ice bodies in the late 1990s. The geodetic mass balances were calculated by differencing digital elevation models derived from several sources. The results indicated a mean cumulative glacier wide mass loss of −40.64 ± 5.19 m w.e. (−0.68 ± 0.09 m w.e. a−1). Within this overall downwasting trend, a positive mass balance of 0.54 ± 0.40 m w.e. a−1 was detected for the period 2000–2009. These estimates agree with the results obtained with the glaciological method during the same time span. Highly negative mass change rates were found from 2010 onwards, with −1.20 ± 0.09 m w.e. a−1 during an unprecedented drought in Central Andes of Chile. The observed area and the elevation changes indicate that the Echaurren Norte Glacier may disappear in the coming years if negative mass balance rates prevail.
Farías-Barahona, D., Vivero, S., Casassa, G., Schaefer, M., Burger, F., Seehaus, T., Iribarren-Anacona, P., Escobar, F., Braun, M.H. „Geodetic Mass Balances and Area changes of Echaurren Norte Glacier (Central Andes, Chile) between 1955 and 2015“. Remote Sensing 11(3), 260. https://doi.org/10.3390/rs11030260
Excluding the large ice sheets of Greenland and Antarctica, glaciers in South America are large contributors to sea-level rise. Their rates of mass loss, however, are poorly known. Here, using repeat bi-static synthetic aperture radar interferometry over the years 2000 to 2011/2015, we compute continent-wide, glacier-specific elevation and mass changes for 85% of the glacierized area of South America. Mass loss rate is calculated to be 19.43 ± 0.60 Gt a−1 from elevation changes above ground, sea or lake level, with an additional 3.06 ± 1.24 Gt a−1 from subaqueous ice mass loss not contributing to sea-level rise. The largest contributions come from the Patagonian icefields, where 83% mass loss occurs, largely from dynamic adjustments of large glaciers. These changes contribute 0.054 ± 0.002 mm a−1 to sea-level rise. In comparison with previous studies, tropical and out-tropical glaciers — as well as those in Tierra del Fuego — show considerably less ice loss. These results provide basic information to calibrate and validate glacier-climate models and also for decision-makers in water resource management.
Braun, M.H., Malz, P., Sommer, C., Farías-Barahona, D., Sauter, T., Casassa, G., Soruco, A., Skvarca, P., Seehaus, T.C. „Constraining glacier elevation and mass changes in South America“. Nature Climate Change, 2019. https://doi.org/10.1038/s41558-018-0375-7
The environmental, socioeconomic and cultural significance of glaciers has motivated several countries to regulate activities on glaciers and glacierized surroundings. However, laws written to specifically protect mountain glaciers have only recently been considered within national political agendas. Glacier Protection Laws (GPLs) originate in countries where mining has damaged glaciers and have been adopted with the aim of protecting the cryosphere from harmful activities. Here, we analyze GPLs in Argentina (approved) and Chile (under discussion) to identify potential environmental conflicts arising from law restrictions and omissions. We conclude that GPLs overlook the dynamics of glaciers and could prevent or delay actions needed to mitigate glacial hazards (e.g. artificial drainage of glacial lakes) thus placing populations at risk. Furthermore, GPL restrictions could hinder strategies (e.g. use of glacial lakes as reservoirs) to mitigate adverse impacts of climate change. Arguably, more flexible GPLs are needed to protect us from the changing cryosphere.
Cite: Iribarren, P., Kinney, J., Schaefer, M., Harrison, S., Wilson, R., Segovia, A., Mazzorana, B., Guerra, F., Farías, D., Reynolds, J., Glasser, NF. (2018). „Glacier protection laws Potential conﬂicts in managing glacial hazards and adapting to climate change“. Ambio, 18 (8), 835-845.
We present a field‐data rich modelling analysis to reconstruct the climatic forcing, glacier response and runoff generation from a high elevation catchment in central Chile over the period 2000‐2015, to provide insights into the differing contributions of debris‐covered and debris‐free glaciers under current and future changing climatic conditions. Model simulations with the physically‐based glacio‐hydrological model TOPKAPI‐ETH reveal a period of neutral or slightly positive mass balance between 2000‐2010, followed by a transition to increasingly large annual mass losses, associated with a recent mega drought. Mass losses commence earlier, and are more severe, for a heavily debris‐covered glacier, most likely due to its strong dependence on snow avalanche accumulation, which has declined in recent years. Catchment runoff shows a marked decreasing trend over the study period, but with high interannual variability directly linked to winter snow accumulation, and high contribution from ice melt in dry periods and drought conditions. The study demonstrates the importance of incorporating local‐scale processes such as snow avalanche accumulation and spatially variable debris thickness, in understanding the responses of different glacier types to climate change. We highlight the increased dependency of runoff from high Andean catchments on the diminishing resource of glacier ice during dry years.
Burger, F., Ayala, A., Farías, D., Shaw, T., MacDonell, S., Brock, B., McPhee, J., Pelliciotti, F. (2018). „Interannual variability in glacier contribution to runoff from a high-elevation Andean catchment: understanding the role of debris cover in glacier hydrology“. Hydrological Process. https://doi.org/10.1002/hyp.13354