Southern Patagonia Icefield Research Articles

Depositional setting of the southern arms of Lago Argentino (southern Patagonia)

ABSTRACT Lago Argentino hosts a series of calving glaciers originating from the Southern Patagonian Icefield, the largest temperate ice cap of the southern hemisphere. Brazo Rico and Brazo Sur are two basins located in the southern part of Lago Argentino, where a series of high-resolution seismic profiles have allowed reconstruction of its depositional setting and sedimentary architecture, and to produce the following maps: top of the acoustic basement, top of the glacial sequence, and thickness of the glacio-lacustrine deposits. Data reveal the role of basement highs in the complex dynamic behavior of the two main glaciers, Perito Moreno and Frías glaciers, which fluctuated along Brazo Rico and Brazo Sur since the end of the Last Glacial Maximum. Their advances and retreats are testified by the presence of several moraine fronts buried beneath a generally undisturbed, glacio-lacustrine and lacustrine sequence, which records the depositional history of the southern arms of Lago Argentino.

Streamflow variations across the Andes (18\xb0\u201355\xb0S) during the instrumental era

The rivers originating in the southern Andes (18°–55°S) support numerous ecosystems and a large number of human populations and socio-economic activities in the adjacent lowlands of Chile, Argentina and Bolivia. Here we show that ca. 75% of the total variance in the streamflow records from this extensive region can be explained by only eight spatially coherent patterns of variability. Five (three) of these Andean patterns exhibit extreme dry (wet) conditions in recent years, with strong interannual variations in northern Chile; long-term drying trends between 31° and 41°S; a transitional pattern in the central Patagonian Andes; and increasing trends in northwestern Argentina and southern Bolivia, the Fueguian Andes, and the eastern portion of the South Patagonian Icefield. Multivariate regression analyses show that large-scale indices of ENSO variability can predict 20% to 45% of annual runoff variability between 28° and 46°S. The influence of Antarctic and North Pacific indices becomes more relevant south of 43°S and in northwestern Argentina and southern Bolivia, respectively, but their overall skill as predictors of Andean streamflows is weak. The analyses provide relevant new information to improve understanding of the spatial coherence, the main temporal features, and the ocean-atmospheric forcings of surface runoff across the southern Andes.

Heterogeneous spatial and temporal pattern of surface elevation change and mass balance of the Patagonian ice fields between 2000 and 2016

Abstract. The northern and southern Patagonian ice fields (NPI and SPI) have been subject to accelerated retreat during the last decades, with considerable variability in magnitude and timing among individual glaciers. We derive spatially detailed maps of surface elevation change (SEC) of NPI and SPI from bistatic synthetic aperture radar (SAR) interferometry data of the Shuttle Radar Topography Mission (SRTM) and TerraSAR-X add-on for Digital Elevation Measurements (TanDEM-X) for two epochs, 2000–2012 and 2012–2016, and provide data on changes in surface elevation and ice volume for the individual glaciers and the ice fields at large. We apply advanced TanDEM-X processing techniques allowing us to cover 90 % and 95 % of the area of NPI and 97 % and 98 % of SPI for the two epochs, respectively. Particular attention is paid to precisely co-registering the digital elevation models (DEMs), accounting for possible effects of radar signal penetration through backscatter analysis and correcting for seasonality biases in case of deviations in repeat DEM coverage from full annual time spans. The results show a different temporal trend between the two ice fields and reveal a heterogeneous spatial pattern of SEC and mass balance caused by different sensitivities with respect to direct climatic forcing and ice flow dynamics of individual glaciers. The estimated volume change rates for NPI are -4.26±0.20 km3 a−1 for epoch 1 and -5.60±0.74 km3 a−1 for epoch 2, while for SPI these are -14.87±0.52 km3 a−1 for epoch 1 and -11.86±1.99 km3 a−1 for epoch 2. This corresponds for both ice fields to an eustatic sea level rise of 0.048±0.002 mm a−1 for epoch 1 and 0.043±0.005 mm a−1 for epoch 2. On SPI the spatial pattern of surface elevation change is more complex than on NPI and the temporal trend is less uniform. On terminus sections of the main calving glaciers of SPI, temporal variations in flow velocities are a main factor for differences in SEC between the two epochs. Striking differences are observed even on adjoining glaciers, such as Upsala Glacier, with decreasing mass losses associated with slowdown of flow velocity, contrasting with acceleration and increase in mass losses on Viedma Glacier.

To improve weather and climate models, researchers are chasing atmospheric gravity waves

On September 3, 2018, an unpowered experimental sailplane made history by flying into the stratosphere. After leaving from El Calafate, a town near the Southern Patagonian Ice Field in Argentina, glider pilots Jim Payne and Tim Gardner surfed on enormous airborne waves emanating from the Andes Mountains. They achieved a world record height of 23,203 meters—higher than a Lockheed U-2 spy plane’s cruising altitude. No other unpowered aircraft has ever achieved such elevation. It was a feat made possible by not just human ingenuity but also the incredible strength of a phenomenon known as atmospheric gravity waves. Atmospheric gravity waves—seen here over the Indian Ocean via the Moderate Resolution Imaging Spectroradiometer housed in NASA’s Terra satellite—emerge when parcels of air are forced upward. Image credit: Jacques Descloitres, MODIS Rapid Response Team, NASA/GSFC. Unlike the similarly named (and perhaps more famous) cosmic gravitational waves, which are ripples in the fabric of space-time, atmospheric gravity waves are a wholly terrestrial occurrence. They emerge when parcels of air are forced upward, for instance, by a tall mountain range, moving from a dense atmospheric layer to a thinner one. The heavier blobs of air then succumb to the force of gravity and fall back down, resulting in a periodic oscillation that can carry energy and momentum over vast distances. They are the smallest atmospheric waves that researchers study, generally between a few hundred meters and a few hundred kilometers in size. But their cumulative effects can be dramatic. The actions of atmospheric gravity waves bring energy from the troposphere—the lowest atmospheric layer, which ends at an altitude of about 10 kilometers—out past the edge of space, 500 or more kilometers above Earth’s surface. They play important roles in daily weather as well as long-term climate fluctuations, decelerating powerful jet streams and affecting the circulating …

Holocene glacier fluctuations on the northern flank of Cordillera Darwin, southernmost South America

Records of past variability afford context for evaluating present-day glacier behavior and for testing hypotheses of climate change. Here, we use 69 radiocarbon dates of wood and other organic materials in association with glacial deposits to document the behavior of Ventisqueros Marinelli and Brooks in Cordillera Darwin over the past ∼17,000 years. Recession from the last glacial maximum was early, with most occurring prior to 17,000 yr BP. Any glacial resurgence during the Antarctic Cold Reversal must have terminated within the bounds of Holocene ice fluctuations. By early Holocene time, Ventisquero Marinelli had retreated such that it was no more extensive than it was in AD 1992. We identify several subsequent glacier readvances, but also note long periods of restricted ice extent, particularly in the mid-Holocene. There were times when Holocene glaciers must have been smaller than at present. Our new record from Marinelli shows similarities to other reconstructions of Holocene glacier variation from southern South America, such as at Mt. Sarmiento and the South Patagonian Icefield, suggesting an underlying climate signal. The overall implication is of substantial early Holocene deglaciation followed by repeated advances interspersed with periods of recession when ice extent was smaller than at present. This general pattern of glacier behavior appears to differ from that of New Zealand's Southern Alps and points to the value of a geographic spread of datasets to elucidate the pattern of Southern Hemisphere climate during the Holocene.

Recent ice dynamics and mass balance of Jorge Montt Glacier, Southern Patagonia Icefield

AbstractThe Southern Patagonia Icefield (SPI) withdrawal in recent decades shows contrasting behaviours between adjacent basins. One of the basins with highest volumetric losses is located at northernmost SPI. We refer to Jorge Montt tidewater glacier (48°30′S/73°30′W, 445 km2in 2018), which retreated 2.7 km between 2011 and 2018 and thinned at rates of up to 21 m a−1over this period. Based on the retreat record, remote-sensing imagery, field data, a mass-balance model and a calving parameterisation, we attempted to differentiate climatic-induced changes (i.e. surface mass balance) and dynamic responses (i.e. calving fluxes). The surface mass balance reached −4.15 km3w.e. a−1between 2012 and 2017. When frontal ablation is included, the net mass balance is −17.79 km3w.e. a−1. This represents a change of trend compared with modelling estimations of positive surface mass balance prior to 2010. This shift is attributed to higher ablation rates given that accumulation is known to have increased between 1980 and 2015. The available evidence, therefore, indicates that frontal ablation is the main factor, supported by observed rates at Jorge Montt as high as 3.81 km3w.e. a−1in 2015, with ice velocities peaking at 11 km a−1.

Late Holocene Glacial Fluctuations of Schiaparelli Glacier at Monte Sarmiento Massif, Tierra del Fuego (54°24′ S)

The Magallanes–Tierra del Fuego region, Southern Patagonia (53–56° S) features a plethora of fjords and remote and isolated islands, and hosts several thousand glaciers. The number of investigated glaciers with respect to the multiple Neoglacial advances is based on a few individual studies and is still fragmentary, which complicates the interpretation of the glacial dynamics in the southernmost part of America. Schiaparelli Glacier (54°24′ S, 70°50′ W), located at the western side of the Cordillera Darwin, was selected for tree-ring-based and radiocarbon dating of the glacial deposits. One focus of the study was to address to the potential dating uncertainties that arise by the use of Nothofagus spp. as a pioneer species. A robust analysis of the age–height relationship, missing the pith of the tree (pith offset), and site-specific ecesis time revealed a total uncertainty value of ±5–9 years. Three adjacent terminal moraines were identified, which increasingly tapered towards the glacier, with oldest deposition dates of 1749 ± 5 CE, 1789 ± 5 CE, and 1867 ± 5 CE. Radiocarbon dates of trunks incorporated within the terminal moraine system indicate at least three phases of cumulative glacial activity within the last 2300 years that coincide with the Neoglacial phases of the Southern Patagonian Icefield and adjacent mountain glaciers. The sub-recent trunks revealed the first evidence of a Neoglacial advance between ~600 BCE and 100 CE, which so far has not been substantiated in the Magallanes–Tierra del Fuego region.

GPS reflectometry study detecting snow height changes in the Southern Patagonia Icefield

Southern Patagonia Icefield (SPI) glaciers have been retreating and shrinking at high rates in recent decades, significantly contributing to sea level rise. In spite of the importance of the SPI, very little is known about its mass balance apart from models lacking in situ validation, such as snow accumulation/ablation at high altitude. On the ground, snow changes are normally measured with stakes planted on snow frequently visited. Automation is possible by the use of ranging sensors, based on laser, radar or ultrasound, installed as part of automatic weather stations. In this study, we use for the first time in the SPI the technique of Global Positioning System Reflectometry (GPS-R) for measuring snow level changes. GPS-R uses observations from GPS satellites tracked by GNSS (Global Navigation Satellite Systems) ground stations. GNSS stations, typically installed according to geodetic network standards for geodynamics purposes (e.g., glacial isostatic rebound studies), inadvertently also record the signal reflected on the snow surface in the antenna surroundings. The GPS-R snow level variations were compared to an ultrasonic sensor installed nearby, operating simultaneously between October 2015 and February 2016. During this period the two datasets exhibited a correlation of 0.91 and an RMS of 17 cm, confirming that GNSS receivers can be used not only for geodetic purposes but also for snow accumulation/ablation monitoring in SPI.

Ice Thickness and Bed Elevation of the Northern and Southern Patagonian Icefields

AbstractThe Northern and Southern Patagonian Icefields are the largest ice masses in the Southern Hemisphere outside Antarctica, but their ice volume and bed topography are poorly known. Here, we combine airborne gravity data collected in 2012 and 2016, with radar data from the Warm Ice Experiment Sounder and Centro de Estudios Científicos's to map bed elevation and ice thickness in great detail. We perform a 3‐D inversion of the gravity data constrained by radar‐derived thickness and fjord bathymetry to infer bed elevation at 500‐m spacing, with a precision of about 60 m. We detect deep glacial valleys with ice thickness exceeding 1,400 m and sectors below sea level on the western branch of Glaciar Pio XI, Occidental, between San Rafael and Colonia, and near Fitz Roy. We calculate an ice volume of 4,756 ± 923 km3 for Northern Patagonia Icefield and Southern Patagonia Icefield, or 40 times the volume of glaciers in the European Alps.

Historical eruptions of Lautaro Volcano and their impacts on lacustrine ecosystems in southern Argentina

Lacustrine sediment sequences were obtained from Lagunas Verde and Gemelas Este, two small lakes located east of the southern Patagonian Ice Field and close to the village of El Chalten, in Argentinian Patagonia. Four tephra layers were identified in each of the short sediment sequences and characterised using individual glass-shard tephra chemistry to determine provenance. Bulk sediment geochemistry and diatom assemblages were analysed to understand the impact of the tephra deposits on the lake ecosystems. Age-depth models for the cores were established by 137Cs and 210Pb dating. Tephra deposits in Laguna Gemelas Este were dated to AD 1986–1998, 1943–1968, 1927–1955, and 1849–1892, and the tephra deposits in Laguna Verde were dated to AD 1940–1970, 1888–1934, 1871–1920, and 1536–1669, the latter interval determined by extrapolation. All tephras had similar geochemical composition and originated from volcanoes in the northern Austral Volcanic Zone. Tephra units were attributed to known historical eruptions and all but one, most likely, were from Lautaro Volcano (49°01′S; 73°33′W). The age of the youngest tephra (AD 1986–1998) from Laguna Gemelas Este points to Viedma Volcano (49°22′S; 73°19′W) as a possible source. Volcanic eruptions had a larger impact on Laguna Verde than on Laguna Gemelas Este, as expressed by changes in δ15N values and diatom communities during tephra deposition. These shifts are explained by perturbations of the nitrogen cycle in the lake, associated with shifts in lacustrine primary production. Primary producers may have been affected by increased water turbidity caused by the ash fall, and consequently, used less nitrogen. Diatom assemblages in Laguna Verde showed marked reductions in numbers of planktonic/tychoplanktonic taxa, in favour of epiphytic/benthic diatom taxa, when tephra was deposited. This contrasts with Laguna Gemelas Este, in which epiphytic/benthic diatom species were generally more abundant and decreases in abundances of planktonic/tychoplanktonic taxa were not as strongly linked to tephra layers as in Laguna Verde. At Laguna Gemelas Este, flatter relief, greater fetch and/or drier climate may have contributed to generally less ecosystem variability, resulting in seemingly less environmental response to volcanic eruptions than in Laguna Verde.

MODIS Image-derived ice surface temperature assessment in the Southern Patagonian Icefield

Ice surface temperature (IST) is one of the most relevant parameters when it comes to estimating the effects of climate change on glaciers. This study aims to estimate the IST for the Southern Patagonian Icefield (SPI) during the 2001–2016 period and, in so doing, to contribute to the assessment of the MOD11A1 product in this area. We evaluated IST performance by comparing it with that of automatic weather stations (AWSs). In addition, the glaciological significance of the results is presented through 1) IST trends, 2) annual IST anomalies, 3) IST behavior at different altitudes and orientations and 4) a comparison with Santa Cruz River flow records. The correlation coefficients obtained between the IST and AWSs ranged between 0.66 and 0.85. In addition, we report on the mean absolute differences between them, ranging between 0.6 ± 3.6°C and 9.4 ± 1.9°C. In this sense, we observed the lowest differences at the AWSs that were located in a homogeneous environment. Stated in glaciological terms: 1) only 1% of the pixels had a statically significant IST trend ( p-value ≤ 0.05): between 0.01 and 0.05°C/month; 2) we found that most of the IST anomalies ranged between –1 and 1°C throughout the period of this study; 3) the results suggest that the altimetric gradient was the most influential variable of the IST, mostly in north-oriented glaciers; and 4) the SPI IST showed an annual periodicity, which, in turn, shows a high correlation with the Santa Cruz River flow ( R = 0.86). This study is the first in estimating the SPI’s IST and contributes to enhance our knowledge of glacier dynamics and, therefore, the management of the water resource. Despite this, some MOD11 filtering is required in regions with high cloud cover frequency.

Assessing Snow Accumulation Patterns and Changes on the Patagonian Icefields

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.

Air Temperature Characteristics, Distribution, and Impact on Modeled Ablation for the South Patagonia Icefield

AbstractThe glaciers of Patagonia are the largest in South America and are shrinking rapidly, raising concerns about their contribution to sea level rise in the face of ongoing climatic change. However, modeling studies forecasting future glacier recession are limited by the scarcity of measured on‐glacier air temperatures and thus tend to use spatially and temporally constant lapse rates. This study presents 9 months of air temperature observations. The network consists of five automatic weather stations and three on‐glacier air temperature sensors installed on the South Patagonia Icefield along a transect at 48°45′S. Observed lapse rates are, overall, steeper on the east (−0.0072 °C/m) compared to the west (−0.0055 °C/m) and vary between the lower section (tongue, ablation zone) and the upper section (plateau, accumulation zone) of the glaciers. Warmer off‐glacier temperatures are found in the east compared to the west for similar elevations. However, on‐glacier observations suggest that the glacier cooling effect is higher in the east compared to the west. Through application of distributed temperature‐index and point‐scale energy balance models we show that modeled ablation rates vary by up to 60%, depending on the air temperature extrapolation method applied, and that melt is overestimated and sublimation is underestimated if the glacier cooling effect is not included in the distributed air temperature data. These results can improve current and future modeling efforts of the energy and mass balance of the whole South Patagonia Icefield.

Glaciological traverse across the Southern Patagonian Icefield

Glaciological traverse across the Southern Patagonian Icefield

The metamorphic rocks of the Nunatak Viedma in the Southern Patagonian Andes: Provenance sources and implications for the early Mesozoic Patagonia-Antarctic Peninsula connection

The Nunatak Viedma within the Southern Patagonian Icefield has been considered as a volcanic center based on its geomorphologic features, despite the fact that field explorations by Eric Shipton determined its metamorphic nature 70 years ago. We carried out fieldwork to characterize this isolated outcrop and performed the first U-Pb dating in detrital zircons from the basement rocks located inside the Southern Patagonian Icefield. We recognized very-low grade metamorphic rocks, corresponding principally to metapelites and metapsammites, and scarce metabasites. Detrital zircons in three metapsammitic samples (composite group of 240 grains) yielded prominent age population peaks at ∼1090, ∼960, ∼630, ∼520, ∼480–460, ∼380, ∼290–260, ∼235-225 Ma that are typical of Gondwanide affinity, and youngest grains at ∼208 Ma. Maximum depositional ages of 225, 223 and 212 Ma were calculated for each sample from the youngest cluster of ages. This distinctive and novelty Late Triassic age justifies differentiate the Nunatak Viedma Unit from the Devonian-early Carboniferous and Permian-Early Triassic (?) belts of the Eastern Andean Metamorphic Complex. Possible primary source areas for the detrital zircons are outcropping in southern Patagonia, the Antarctic Peninsula, and the Malvinas Islands. Additionally, secondary sources could be part of the erosion and recycling of metasediments from the Eastern Andean Metamorphic Complex. We propose that the cluster of Triassic ages is related to the volcanic arc emplaced along the Antarctic Peninsula and active at that time when was still attached to southern Patagonia during the Triassic. The dynamics of the early Mesozoic orogen is also discussed.

Glaciar Pío XI: La excepción a la tendencia de desglaciaciónen Patagonia

The Pio XI glacier also called Bruggen (49o13'S 74oW), the largest glacial basin of the Southern Patagonian Ice Field (SPI), has experienced a net increase in area of 126 km2 since 1945 due to an almost permanent state of advance with rates of 150 m/a and a thickening of 2 m/a between 1975 and 2013. This behaviour is an anomaly in Patagonia, since it is the only glacier with a net advance throughout the SPI. Most of the rest of the glaciers of the SPI have lost mass at high rates, highlighting the losses of Jorge Montt and O’Higgins among many others. Several hypotheses have been proposed to explain the anomalous behaviour of Pio XI, particularly the presence of surging events that have occurred in several occasions, but so far there is no certainty of the causes that explain its complex behaviour. However, it is estimated that the topographic features of the glacier, in particular the presence in the accumulation zone of the active volcan Lautaro, the highest peak of the SPI, and a little more to the south the presence of the Cordon Mariano Moreno, the second highest mountain of the SPI, are a formidable barrier of about 55 km north-south for the prevailing westerly winds, generating the largest amounts of solid precipitation of all the CHS. The process of glacial advance has repressed lateral valleys generating numerous proglacial lakes, and in its term, it is forming a frontal moraine due to the high sedimentation rates, significantly reducing the calving area.

Lagrangian Detection of Moisture Sources for the Southern Patagonia Icefield (1979–2017)

The origin of moisture for the Southern Patagonia Icefield and the transport of moisture towards it are not yet fully understood. These quantities have a large impact on the stable isotope composition of the icefield, adjacent lakes and nearby vegetation, and is hard to quantify from observations. Clearly identified moisture sources help to interpret anomalies in the stable isotope compositions and contribute to paleoclimatological records from the icefield and the close surrounding. This study detects the moisture sources of the icefield with a Lagrangian moisture source method. The kinematic 18-day backward trajectory calculations use reanalysis data from the European Centre for Medium-Range Weather Forecasts (ERA-Interim) from January 1979 to January 2017. The dominant moisture sources are found in the South Pacific Ocean from 80◦ W to 160◦ W and 30◦S to 60◦ S. A persistent anticyclone in the subtropics and advection of moist air by the prevailing westerlies are the principal flow patterns. Most of the moisture travels less than 10 days to reach the icefield. The majority of the trajectories originate from above the planetary boundary layer but enter the Pacific boundary layer to reach the maximum moisture uptake 2 days before arrival. During the last day trajectories rise as they encounter topography. The location of the moisture sources are influenced by seasons, Antarctic Oscillation, El-Nino Southern Oscillation, and the amount of monthly precipitation, which can be explained by variations in the location and strength of the westerly wind belt.”

Estimation of surface flow speed and ice surface temperature from optical satellite imagery at Viedma glacier, Argentina

Abstract The Viedma glacier is the largest glacier in Argentina and one of the most dynamic in the Southern Patagonian Icefield. It is a strategic water source. This study analyzes the interactions of glaciological variables that help better explain the behavior of the Viedma glacier. This paper presents the study of surface flow speed and ice surface temperatures during the 2015–2016 warm season by using remote sensing data and includes the statistical correlation between those variables. In addition, a reconstruction of the front fluctuation between 1979 and 2016 through CORONA and LANDSAT images is included. Finally, the displacement modes dominating the Viedma glacier are suggested. Our results showed that the mean surface flow speed during the study period was of around 1.2 ± 0.3 md−1 and reached maximum values of 5.5 ± 0.3 md−1 and 3 ± 0.3 md−1 at middle basin and terminus respectively. Thermal data revealed minimum values of −2 °C in the uppermost section of the study area, whilst the glacier's terminus showed supraglacial melt (values above pressure melting point). Front fluctuation analysis revealed the largest front retraction of the last 40 years between 2010 and 2016: around 281 my−1. Statistical correlation analysis and glaciological data suggested that the middle and lower basins of the Viedma glacier are widely dominated by basal sliding.

Glacier Mass Changes of Lake-Terminating Grey and Tyndall Glaciers at the Southern Patagonia Icefield Derived From Geodetic Observations and Energy and Mass Balance Modeling

In this study we demonstrate how energy and mass fluxes vary in space and time for Grey and Tyndall glaciers at the Southern Patagonia Icefield (SPI). Despite the overall glacier retreat of most Patagonian glaciers, a recent increase in mass loss has been observed, but individual glaciers respond differently in terms of spatial and temporal changes. In this context, the detailed investigation of the effect of mass balance processes on recent glacier response to climate forcing still needs refinement. We therefore quantify surface energy-fluxes and climatic mass balance of the two neighboring glaciers, Grey and Tyndall. The COupled Snow and Ice energy and MAss balance model COSIMA is applied to assess recent surface energy and climatic mass balance variability with a high temporal and spatial resolution for a 16-year period between April 2000 to March 2016. The model is driven by downscaled 6-hourly atmospheric data derived from ERA-Interim reanalysis and MODIS/Terra Snow Cover and validated against ablation measurements made in single years. High resolution precipitation fields are determined by using an analytical orographic precipitation model. Frontal ablation is estimated as residual of climatic mass balance and geodetic mass balance derived from TanDEM-X/SRTM between 2000 and 2014. We simulate a positive glacier-wide mean annual climatic mass balance of +1.02$\pm$0.52\,m\,w.e. a$^{-1}$ for Grey Glacier and of +0.68$\pm$0.54\,m\,w.e. a$^{-1}$ for Tyndall Glacier between 2000 and 2014. Climatic mass balance results show a high year to year variability. Comparing climatic mass balance results with previous studies underlines the high uncertainty in climatic mass balance modeling with respect to accumulation on the SPI. Due to the lack of observations accumulation estimates differ from previous studies based on the methodological approaches. Mean annual ice loss by frontal ablation is estimated to be 2.07$\pm$0.70\,m\,w.e.\,a$^{-1}$ for Grey Glacier and 3.26$\pm$0.82\,m\,w.e.\,a$^{-1}$ for Tyndall Glacier between 2000 and 2014. Ice loss by surface ablation exceeds ice loss by frontal ablation for both glaciers. The overall mass balance of Grey and Tyndall glaciers are clearly negative with -1.05$\pm$0.18\,m\,w.e.\,a$^{-1}$ and -2.58$\pm$0.28\,m\,w.e.\,a$^{-1}$ respectively.

Factors controlling alpine glaciations in the Sierra Baguales Mountain Range of southern Patagonia (50º S), inferred from the morphometric analysis of glacial cirques

The Sierra Baguales Mountain Range, forming the eastern foothills of the Southern Patagonian Andes, has well-developed alpine-glaciated landforms which present an ideal opportunity to study climatic and non-climatic factors that control cirque development and morphology. One hundred and forty-three glacial cirques were studied with reference to 14 morphometric attributes which were analyzed using statistical analysis and GIS methodologies. The cirques were classified into two types using cluster analysis complimented with a composite map based on the attributes, the latter technique that is applied to glacial cirque analysis for the first time. Type 1 cirques are associated with glacial processes isolated from the Southern Patagonian Ice Field (SPIF), developed under locally cold and dry climatic conditions. Type 2 glacial cirques are associated with older, more extensive glacial processes controlled by regional-scale climate variables and the presence of the Pleistocene Ice Sheet. The results show that the development of most of the glacial cirques has been controlled mainly by their aspect, exposure to solar radiation, Southern Hemisphere Westerly winds, and cirque floor slope. Finally, we concluded that our analyses show the evolution of cirques in the Sierra Baguales Mountain Range was not uniform. Cirque glaciers that developed to the west, close to the Southern Patagonian Ice field, have been more dynamic, and therefore their cirques experienced more erosion than those located to the east.