Regression-based gap-filling methods show air temperature reductions and wind pattern changes during the 2019 total eclipse in Chile

Singular disruptive events like solar eclipses affect the measured values of meteorological variables at the earth’s surface. To quantify such an impact, it is necessary to estimate what value the parameter would have taken had the event not occurred. We design and compare several methods to perform such an estimate based on longer observational timeseries from individual meteorological surface stations. Our methods are based on regularised regressions (including a Bayesian variant) and provide both a point an associated error estimate of the disruptive event’s impact. With their help, we study the effect of the total solar eclipse of July 2nd, 2019, in the Coquimbo Region of Chile, on near-surface air temperatures and winds. The observational data used have been collected by the meteorological surface station network of the Centro de Estudios Avanzados en Zonas Áridas (CEAZA). Most stations inside the eclipse’s umbra registered a temperature drop of 1–2 °C, while the most extreme estimated temperature drop surpassed 6 °C. The presence of an ‘eclipse cyclone’ can neither be proven nor refuted. Application of the regression methods to other comparable problems like volcanic eruptions, forest fires, or simply gap filling of observational data, are conceivable

Brief communication: A framework to classify glaciers for water resource evaluation and management in the Southern Andes

Over the last 2 decades the importance of Andean glaciers, particularly as water resources, has been recognized in both scientific literature and the public sphere. This has led to the inclusion of glaciers in the environmental impact assessment and the development of glacier protection laws in both Chile and Argentina. However, these laws are limited in their ability to protect, manage, and monitor water resources as they do not differentiate between glacier types. We propose three glacier categories that aim to group glaciers based on their sensitivity to environmental changes as a framework that could be adopted to match the level of protection to the current and future needs of society, be region-specific, and evolve through time. Finally, we review both national inventories with respect to this classification to facilitate the evaluation and/or management of water resources

Recent Deceleration of the Ice Elevation Change of Ecology Glacier (King George Island, Antarctica)

Glacier change studies in the Antarctic Peninsula region, despite their importance for global sea level rise, are commonly restricted to the investigation of frontal position changes. Here we present a long term (37 years; 1979–2016) study of ice elevation changes of the Ecology Glacier, King George Island ( 62 ∘ 11 ′ S, 58 ∘ 29 ′ W). The glacier covers an area of 5.21 km 2 and is located close to the H. Arctowski Polish Antarctic Station, and therefore has been an object of various multidisciplinary studies with subject ranging from glaciology, meteorology to glacial microbiology. Hence, it is of great interest to assess its current state and put it in a broader context of recent glacial change. In order to achieve that goal, we conducted an analysis of archival cartographic material and combined it with field measurements of proglacial lagoon hydrography and state-of-art geodetic surveying of the glacier surface with terrestrial laser scanning and satellite imagery. Overall mass loss was largest in the beginning of 2000s, and the rate of elevation change substantially decreased between 2012–2016, with little ice front retreat and no significant surface lowering. Ice elevation change rate for the common ablation area over all analyzed periods (1979–2001–2012–2016) has decreased from −1.7 ± 0.4 m/year in 1979–2001 and −1.5 ± 0.5 m/year in 2001–2012 to −0.5 ± 0.6 m/year in 2012–2016. This reduction of ice mass loss is likely related to decreasing summer temperatures in this region of the Antarctic Peninsula

The Snowline and 0°C Isotherm Altitudes During Precipitation Events in the Dry Subtropical Chilean Andes as Seen by Citizen Science, Surface Stations, and ERA5 Reanalysis Data

Understanding the variability of the snowline and the closely related 0°C isotherm during infrequent precipitation events in the dry Andes in Chile is fundamental for precipitation, snow cover, and discharge predictions. For instance, it is known that on the windward side of mountains, the 0°C isotherm can be several hundreds of meters lower than on the free air upwind counterpart, but little is understood about such effects in the Andes due to missing in situ evidence on the precipitation phase. To bridge this gap, 111 photographs of the snowline after precipitation events between 2011 and 2021 were gathered in the frame of a citizen science programme to estimate the snowline altitude. Since photographs of the mountain snowline are in good agreement with Sentinel-2 imagery, they have great potential to validate empirical snowline estimations. Using the snowline altitude from the photos, we evaluated different methods to estimate the snowline and 0°C isotherm altitude during precipitation events based on surface meteorological observations and ERA5 reanalysis data. We found a high correlation between the observed snowline altitude and the extrapolated 0°C isotherm based on constant lapse rates (−5.5 to −6.5°C km−1) applied to air temperature from single, near stations. However, uncertainty increases for distances >10 km. The results also indicate that the linear regression method is a good option to estimate ZSL, but the results strongly depend on the availability of high-elevation station datasets. During half of the precipitation events, the 0°C isotherm lies between ∼1,800 and ∼2,400–2,500 m asl. in winter, and the snowline is on average ∼280 m below this altitude. Our results indicate the presence of a mesoscale lowering of the 0°C isotherm over the windward slopes compared to the free-air upwind value during precipitation events and a possible isothermal layer of near-freezing air temperatures comparable to other mountain ranges. Due to this mesoscale and local behavior, ERA5 data generally overestimate the snow–rain transition in high-elevation areas, especially for relatively intense events. On the other hand, the 0°C isotherm altitude is underestimated if only low-elevation valley stations are considered, highlighting the importance of high-altitude meteorological stations in the network.Fil: Schauwecker, Simone. Centro de Estudios Avanzados En Zonas Áridas; ChileFil: Palma, Gabriel. Centro de Estudios Avanzados En Zonas Áridas; ChileFil: MacDonell, Shelley. University of Canterbury; Nueva Zelanda. Centro de Estudios Avanzados En Zonas Áridas; ChileFil: Ayala, Álvaro. Centro de Estudios Avanzados En Zonas Áridas; ChileFil: Viale, Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentin

Automated detection of rock glaciers using deep learning and object-based image analysis

B Robson was supported by the Meltzer foundation and a University of Bergen grant. S MacDonell was supported by CONICYT-Programa Regional (R16A10003) and the Coquimbo Regional Government via FIC-R(2016)BIP 40000343. D. Hölbling has been supported by the Austrian Science Fund through the project MORPH (Mapping, Monitoring and Modeling the Spatio-Temporal Dynamics of Land Surface Morphology; FWF-P29461-N29). N Schaffer was financed by CONICYT-FONDECYT (3180417) and P Rastner by the ESA Dragon 4 programme (4000121469/17/I-NB).Rock glaciers are an important component of the cryosphere and are one of the most visible manifestations of permafrost. While the significance of rock glacier contribution to streamflow remains uncertain, the contribution is likely to be important for certain parts of the world. High-resolution remote sensing data has permitted the creation of rock glacier inventories for large regions. However, due to the spectral similarity between rock glaciers and the surrounding material, the creation of such inventories is typically conducted based on manual interpretation, which is both time consuming and subjective. Here, we present a novel method that combines deep learning (convolutional neural networks or CNNs) and object-based image analysis (OBIA) into one workflow based on freely available Sentinel-2 optical imagery (10 m spatial resolution), Sentinel-1 interferometric coherence data, and a digital elevation model (DEM). CNNs identify recurring patterns and textures and produce a prediction raster, or heatmap where each pixel indicates the probability that it belongs to a certain class (i.e. rock glacier) or not. By using OBIA we can segment the datasets and classify objects based on their heatmap value as well as morphological and spatial characteristics. We analysed two distinct catchments, the La Laguna catchment in the Chilean semi-arid Andes and the Poiqu catchment in the central Himalaya. In total, our method mapped 108 of the 120 rock glaciers across both catchments with a mean overestimation of 28%. Individual rock glacier polygons howevercontained false positives that are texturally similar, such as debris-flows, avalanche deposits, or fluvial material causing the user's accuracy to be moderate (63.9–68.9%) even if the producer's accuracy was higher (75.0–75.4%). We repeated our method on very-high-resolution Pléiades satellite imagery and a corresponding DEM (at 2 m resolution) for a subset of the Poiqu catchment to ascertain what difference image resolution makes. We found that working at a higher spatial resolution has little influence on the producer's accuracy (an increase of 1.0%), however the rock glaciers delineated were mapped with a greater user's accuracy (increase by 9.1% to 72.0%). By running all the processing within an object-based environment it was possible to both generate the deep learning heatmap and perform post-processing through image segmentation and object reshaping. Given the difficulties in differentiating rock glaciers using image spectra, deep learning combined with OBIA offers a promising method for automating the process of mapping rock glaciers over regional scales and lead to a reduction in the workload required in creating inventories.Publisher PDFPeer reviewe

Glacier and rock glacier changes since the 1950s in the La Laguna catchment, Chile

Benjamin Aubrey Robson was supported by a University of Bergen mobility grant for this work. This work was also supported by ANID and Concurso de Fortalecimiento al Desarrollo Científico de Centros Regionales (grant no. 2020-R20F0008-CEAZA), and Álvaro Ayala was supported by ANID and FONDECYT (grant no. 3190732).Glaciers and rock glaciers play an important role in the hydrology of the semi-arid northern Chile. Several studies show that glaciers have rapidly lost mass in response to climate change during the last decades. The response of rock glaciers to climate change in this region is, however, less known. In this study we use a combination of historical aerial photography, stereo satellite imagery, airborne lidar, and the Shuttle Radar Topography Mission (SRTM) DEM to report glacier changes for the Tapado Glacier-rock glacier complex from the 1950s to 2020 and to report mass balances for the glacier component of the complex, Tapado Glacier. Furthermore, we examine high-resolution elevation changes and surface velocities between 2012 and 2020 for 35 rock glaciers in the La Laguna catchment. Our results show how Tapado Glacier has shrunk by -25.2 +/- 4.6 % between 1956 and 2020, while the mass balance of Tapado Glacier has become steadily more negative, from being approximately in balance between 1956 and 1978 (-0.04 +/- 0.08 m w.e. a(-1)) to showing increased losses between 2015 and 2020 (-0.32 +/- 0.08 m w.e. a(-1)). Climatological (re-)analyses reveal a general increase in air temperature, decrease in humidity, and variable precipitation since the 1980s in the region. In particular, the severe droughts starting in 2010 resulted in a negative mass balance of -0.54 +/- 0.10 m w.e. a(-1) between 2012 and 2015. The rock glaciers within the La Laguna catchment show heterogenous changes, with some sections of landforms exhibiting pronounced elevation changes and surface velocities exceeding that of Tapado Glacier. This could be indicative of high ice contents within the landforms and also highlights the importance of considering how landforms can transition from more glacial landforms to more periglacial features under permafrost conditions. As such, we believe high-resolution (sub-metre) elevation changes and surface velocities are a useful first step for identifying ice-rich landforms.Publisher PDFPeer reviewe

Contrasting geophysical signatures of a relict and an intact Andean rock glacier

In semi-arid Chile, rock glaciers cover more surface area than glaciers and are potentially important water reserves. To understand their current and future hydrological role, it is necessary to characterize their internal structure (e.g. internal boundaries and ice, air, water and rock content). In this study, we present the results and interpretations of profiles of electrical resistivity and refraction seismic tomography collected on two contrasting rock glaciers in the Chilean Andes located at the headwaters of the Elqui River within the Estero Derecho nature reserve. These geophysical measurements are interpreted both independently and jointly through a scheme of petrophysical four-phase inversion. These first in situ measurements in Estero Derecho confirm that El Ternero (intact rock glacier) contains a significant volume of ground ice, while El Jote contains little to no ice (relict rock glacier). Within our study, we highlight the strong differences in the geophysical responses between intact and relict rock glaciers and propose a diagnostic model that differentiates between them

Interannual variability in glacier contribution to runoff from a high-elevation Andean catchment: understanding the role of debris cover in glacier hydrology

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 and 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

Evaluation of MODIS-derived estimates of the albedo over the Atacama Desert using ground-based spectral measurements

Surface albedo is an important forcing parameter that drives the radiative energy budget as it determines the fraction of the downwelling solar irradiance that the surface reflects. Here we report on ground-based measurements of the spectral albedo (350–2200 nm) carried out at 20 sites across a North–South transect of approximately 1300 km in the Atacama Desert, from latitude 18° S to latitude 30° S. These spectral measurements were used to evaluate remote sensing estimates of the albedo derived from the Moderate Resolution Imaging Spectroradiometer (MODIS). We found that the relative mean bias error (RMBE) of MODIS-derived estimates was within ± 5% of ground-based measurements in most of the Atacama Desert (18–27° S). Although the correlation between MODIS-derived estimates and ground-based measurements remained relatively high (R= 0.94), RMBE values were slightly larger in the southernmost part of the desert (27–30° S). Both MODIS-derived data and ground-based measurements show that the albedo at some bright spots in the Atacama Desert may be high enough (up to 0.25 in visible range) for considerably boosting the performance of bifacial photovoltaic technologies (6–12%)

Black carbon in the Southern Andean snowpack

The Andean snowpack is an important source of water for many communities. As other snow-covered regions around the world, the Andes are sensitive to black carbon (BC) deposition from fossil fuel and biomass combustion. BC darkens the snow surface, reduces the albedo, and accelerates melting. Here, we report on measurements of the BC content conducted by using the meltwater filtration (MF) technique in snow samples collected across a transect of more than 2500 km from the mid-latitude Andes to the southern tip of South America. Addressing some of the key knowledge gaps regarding the effects of the BC deposition on the Andean snow, we identified BC-impacted areas, assessed the BC-related albedo reduction, and estimated the resulting snow losses. We found that BC concentrations in our samples generally ranged from 2 to 15 ng g-1, except for the nearly BC-free Patagonian Icefields and for the BC-impacted sites nearby Santiago (a metropolis of 6 million inhabitants). We estimate that the seasonal snowpack shrinking attributable to the BC deposition ranges from 4 mm water equivalent (w.e.) at relatively clean sites in Patagonia to 241 mm w.e. at heavily impacted sites close to Santiago. © 2022 The Author(s). Published by IOP Publishing Ltd