Stable water isotopes of precipitation and firn cores from the northern Antarctic Peninsula region as a proxy for climate reconstruction

In order to investigate the climate variability in the northern Antarctic Peninsula region, this paper focuses on the relationship between stable isotope content of precipitation and firn, and main meteorological variables (air temperature, relative humidity, sea surface temperature, and sea ice extent). Between 2008 and 2010, we collected precipitation samples and retrieved firn cores from several key sites in this region. We conclude that the deuterium excess oscillation represents a robust indicator of the meteorological variability on a seasonal to sub-seasonal scale. Low absolute deuterium excess values and the synchronous variation of both deuterium excess and air temperature imply that the evaporation of moisture occurs in the adjacent Southern Ocean. The δ<sup>18</sup>O-air temperature relationship is complicated and significant only at a (multi)seasonal scale. Backward trajectory calculations show that air-parcels arriving at the region during precipitation events predominantly originate at the South Pacific Ocean and Bellingshausen Sea. These investigations will be used as a calibration for ongoing and future research in the area, suggesting that appropriate locations for future ice core research are located above 600 m a.s.l. We selected the Plateau Laclavere, Antarctic Peninsula as the most promising site for a deeper drilling campaign

Stratigraphic analysis of firn cores from an antarctic ice shelf firn aquifer

Indexación ScopusIn recent decades, several large ice shelves in the Antarctic Peninsula region have experienced significant ice loss, likely driven by a combination of oceanic, atmospheric and hydrological processes. All three areas need further research, however, in the case of the role of liquid water the first concern is to address the paucity of field measurements. Despite this shortage of field observations, several authors have proposed the existence of firn aquifers on Antarctic ice shelves, however little is known about their distribution, formation, extension and role in ice shelf mechanics. In this study we present the discovery of saturated firn at three drill sites on the Müller Ice Shelf (67°14' S; 66°52' W), which leads us to conclude that either a large contiguous or several disconnected smaller firn aquifers exist on this ice shelf. From the stratigraphic analysis of three short firn cores extracted during February 2019 we describe a new classification system to identify the structures and morphological signatures of refrozen meltwater, identify evidence of superficial meltwater percolation, and use this information to propose a conceptual model of firn aquifer development on the Müller Ice Shelf. The detailed stratigraphic analysis of the sampled cores will provide an invaluable baseline for modelling studies. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.https://www.mdpi.com/2073-4441/13/5/73

Climate and environmental changes of the Lategacial transition and Holocene in northeastern Siberia: Evidence from diatom oxygen isotopes and assemblage composition at Lake Emanda

Indexación ScopusA new dataset from Lake Emanda provides insights into climate and environmental dynamics in an extreme continental setting in northeastern Siberia. The δ18Odiatom record is supported by diatom assemblage analysis, modern isotope hydrology and atmospheric circulation patterns. The data reveal a relatively cold oligotrophic freshwater lake system persisting for the last ∼13.2 cal ka BP. Most recent δ18Odiatom (+21.5‰) combined with present-day average δ18Olake (−16.5‰) allows calculating Tlake (∼21 °C), reflecting summer conditions. Nonetheless, the δ18Odiatom variability is associated with changes in δ18Olake rather than with Tlake. An obvious shift of ∼2‰ in the δ18Odiatom record at 11.7–11.5 cal ka BP accompanied by significant changes in diatom assemblages reflects the onset of the Holocene. Relatively high δ18Odiatom during the Early Holocene suggests relatively warm and/or dry climate with associated evaporation effects. The absolute maximum in δ18Odiatom of +27.7‰ consistent with high values of diatom indices at ∼7.9–7.0 cal ka BP suggests a Mid Holocene Thermal Maximum. A continuous depletion in δ18Odiatom since ∼5.0 cal ka BP is interpreted as Middle to Late Holocene cooling reaching the absolute minimum at 0.4 cal ka BP (i.e. the Little Ice Age). An overall cooling trend (∼0.3‰ 1000 yr−1) throughout the Holocene follows decreasing solar insolation. The pattern of the Lake Emanda δ18Odiatom record is similar to that obtained from Lake El'gygytgyn suggesting a common “eastern” regional signal in both records, despite their hydrological differences. Presently, atmospheric moisture reaches the study region from the west and east with ∼40% each, as well as ∼20% from the north. © 2021 The Author(s)https://www-sciencedirect-com.recursosbiblioteca.unab.cl/science/article/pii/S0277379121001128?via%3Dihu

Major atmospheric particulate matter sources for glaciers in Coquimbo Region, Chile

Tapado Glacier is a subtropical mountain glacier in the Coquimbo region of Chile that has been continuously retreating during the last 60 years due to diminishing precipitation rates and rising temperatures and likely due to a currently unknown influence from atmospheric pollutant deposition. Climatic and meteorological impacts on this, and other, Andean glacier have been previously studied; however, cryosphere changes driven by aerosols are still largely unknown. To contribute to the understanding of the origin of aerosols and their dispersion, this study aims to identify natural and anthropogenic sources of air pollution deposited on the Tapado Glacier (4500–5536 m a.s.l.) and their transport by using a receptor model (positive matrix factorization) together with the concentration of major ions as proxies of air pollution deposited on this glacier. This model’s outcomes were complemented with daily wind backward trajectories computed for a whole year using the HYSPLYT meteorological model. Four sources were identified as the main contributors to major soluble ions in the Tapado surface snow. These sources are natural Aeolian dust (38%) from the Atacama Desert (including mining sites), natural weathered sulphates (27%), anthropogenic nitrates (25%), and coastal aerosols (10%). Coastal nitrate emissions and coastal aerosols are both sources with an important anthropogenic component, coming from La Serena and Coquimbo’s coastal cities. The crustal components and sulphate profiles are similar to detritus dispersed from the glacier after wind erosion. Although the glacier is located over 4000 m above sea level, anthropogenic pollutants reached this location. However, their contributions were smaller compared to natural contaminants. Our findings can likely be extended to the nearest glaciers in Northern Chile, which have similar potential contaminant sources from cities, ports, and thriving mining activity. However, these findings may not be suitable for southern Chilean glaciers, which are closer to bigger cities and to smoke from residential heating prevalent in winter months and wildfires during the summer

Hydrological connections in a glaciated Andean catchment under permafrost conditions (33°S)

Fresh water supply is critical along the Andes, where drought conditions over the past decade are projected to persist. At high Andean headwater catchments, frozen ground conditions are assumed to modulate groundwater flow paths and their hydrological signals at different timescales. However, knowledge of hydrological connections in subtropical Andean catchments is still very sparse. This study assessed hydrological connections and their impacts on groundwater contribution to baseflow in a headwater proglacial aquifer located in central Chile at 33° S and 3600 m a.s.l. We collected and analyzed snow, glacial stream, and groundwater spring water samples between 2019 and 2021. We combined of water isotope and metagenomic proxies with the hydraulic parameterization of the catchment to deliver mean transit time distributions through the proglacial aquifer. The new hydrological insights for the region include the finding that groundwater spring signals delivered sub-decadal transit times, implying likely origins from glacial or interstitial ice. Additionally, the stable isotope signature showed that groundwater consistently differs from snow and surface runoff. The 16S rRNA metabarcoding analyses demonstrated the presence of psychrophilic microorganisms in groundwater springs, supporting the idea of a late warm-season activation of interstitial ice due to thawing events associated with a differential relative-abundance of specific cryophilic bacteria. Finally, our results suggest hydrological connections and dampening timeframes between glaciers, proglacial areas, and groundwater springs, most likely from thawing sources

New insights into the use of stable water isotopes at the northern Antarctic Peninsula as a tool for regional climate studies

Due to recent atmospheric and oceanic warming, the Antarctic Peninsula is one of the most challenging regions of Antarctica to understand in terms of both local-and regional-scale climate signals. Steep topography and a lack of long-term and in situ meteorological observations complicate the extrapolation of existing climate models to the sub-regional scale. Therefore, new techniques must be developed to better understand processes operating in the region. Isotope signals are traditionally related mainly to atmospheric conditions, but a detailed analysis of individual components can give new insight into oceanic and atmospheric processes. This paper aims to use new isotopic records collected from snow and firn cores in conjunction with existing meteorological and oceanic datasets to determine changes at the climatic scale in the northern extent of the Antarctic Peninsula. In particular, a discernible effect of sea ice cover on local temperatures and the expression of climatic modes, especially the Southern Annular Mode (SAM), is demonstrated. In years with a large sea ice extension in winter (negative SAM anomaly), an inversion layer in the lower troposphere develops at the coastal zone. Therefore, an isotope-temperature relationship (δ-T) valid for all periods cannot be obtained, and instead the δ-T depends on the seasonal variability of oceanic conditions. Comparatively, transitional seasons (autumn and spring) have a consistent isotope-temperature gradient of +0.69‰ °C¯¹. As shown by firn core analysis, the near-surface temperature in the northern-most portion of the Antarctic Peninsula shows a decreasing trend (-0.33°C year¯¹) between 2008 and 2014. In addition, the deuterium excess (dexcess) is demonstrated to be a reliable indicator of seasonal oceanic conditions, and therefore suitable to improve a firn age model based on seasonal dexcess variability. The annual accumulation rate in this region is highly variable, ranging between 1060 and 2470kg m¯²year¯¹ from 2008 to 2014. The combination of isotopic and meteorological data in areas where data exist is key to reconstruct climatic conditions with a high temporal resolution in polar regions where no direct observations exist

New insights into the use of stable water isotopes at the northern Antarctic Peninsula as a tool for regional climate studies

Due to recent atmospheric and oceanic warming, the Antarctic Peninsula is one of the most challenging regions of Antarctica to understand in terms of both local- and regional-scale climate signals. Steep topography and a lack of long-term and in situ meteorological observations complicate the extrapolation of existing climate models to the sub-regional scale. Therefore, new techniques must be developed to better understand processes operating in the region. Isotope signals are traditionally related mainly to atmospheric conditions, but a detailed analysis of individual components can give new insight into oceanic and atmospheric processes. This paper aims to use new isotopic records collected from snow and firn cores in conjunction with existing meteorological and oceanic datasets to determine changes at the climatic scale in the northern extent of the Antarctic Peninsula. In particular, a discernible effect of sea ice cover on local temperatures and the expression of climatic modes, especially the Southern Annular Mode (SAM), is demonstrated. In years with a large sea ice extension in winter (negative SAM anomaly), an inversion layer in the lower troposphere develops at the coastal zone. Therefore, an isotope–temperature relationship (δ–T) valid for all periods cannot be obtained, and instead the δ–T depends on the seasonal variability of oceanic conditions. Comparatively, transitional seasons (autumn and spring) have a consistent isotope–temperature gradient of +0.69 ‰ °C−1. As shown by firn core analysis, the near-surface temperature in the northern-most portion of the Antarctic Peninsula shows a decreasing trend (−0.33 °C year−1) between 2008 and 2014. In addition, the deuterium excess (dexcess) is demonstrated to be a reliable indicator of seasonal oceanic conditions, and therefore suitable to improve a firn age model based on seasonal dexcess variability. The annual accumulation rate in this region is highly variable, ranging between 1060 and 2470 kg m−2 year−1 from 2008 to 2014. The combination of isotopic and meteorological data in areas where data exist is key to reconstruct climatic conditions with a high temporal resolution in polar regions where no direct observations exist

Improving the underground structural characterization and hydrological functioning of an Andean peatland using geoelectrics and water stable isotopes in semi-arid Chile

High altitude, Andean wetlands, or bofedales as they are locally known, are important regulators of the local water balance and also play a key role in sustaining biodiversity. Nevertheless, there is almost no information regarding their hydrogeological structure and functioning. This paper aims to characterize the thickness of the alluvial filling of one peat-accumulating wetland in North-Central Chile using Electrical Resistivity Tomography (ERT) to assess its role as a water reservoir. To develop a quasi-3D understanding of the peatland’s structure, four ERT profiles were conducted. Results highlight a conductive basin shape of the peatland, with a thicker interface downstream than upstream between alluvial materials and the underlying bedrock or rock screes. Those results allow the estimate of the water column (1000–3400 mm) within the peatland alluvial filling. The second objective is to better understand the water exchanges between the peatland and the streamflow using discharge measurements and water stable isotopes. Water and isotopes budgets highlight a streamflow loss towards the peatland groundwater reservoir at the end of spring season. In addition, ten δ¹⁸O and δ²H surveys were used to characterize the distinct wetland water sources and their temporal variations. A peatland conceptual model is proposed to connect groundwater, rock glaciers, snowmelt, and hillslope flows. Andean peatlands provide a pivotal control on water delivery downstream, and therefore, understanding their structure and function is important, because they are unique structures providing ecological services at high elevations

Black carbon and other light-absorbing impurities in snow in the Chilean Andes

Vertical profiles of black carbon (BC) and other light-absorbing impurities were measured in seasonal snow and permanent snowfields in the Chilean Andes during Austral winters 2015 and 2016, at 22 sites between latitudes 18°S and 41°S. The samples were analyzed for spectrally-resolved visible light absorption. For surface snow, the average mass mixing ratio of BC was 15 ng/g in northern Chile (18–33°S), 28 ng/g near Santiago (a major city near latitude 33°S, where urban pollution plays a significant role), and 13 ng/g in southern Chile (33–41°S). The regional average vertically-integrated loading of BC was 207 µg/m² in the north, 780 µg/m²near Santiago, and 2500 µg/m² in the south, where the snow season was longer and the snow was deeper. For samples collected at locations where there had been no new snowfall for a week or more, the BC concentration in surface snow was high (~10–100 ng/g) and the sub-surface snow was comparatively clean, indicating the dominance of dry deposition of BC. Mean albedo reductions due to light-absorbing impurities were 0.0150, 0.0160, and 0.0077 for snow grain radii of 100 µm for northern Chile, the region near Santiago, and southern Chile; respective mean radiative forcings for the winter months were 2.8, 1.4, and 0.6 W/m² . In northern Chile, our measurements indicate that light-absorption by impurities in snow was dominated by dust rather than BC

Elemental and mineralogical composition of the Western Andean snow (18°S–41°S)

The snowpack is an important source of water for many Andean communities. Because of its importance, elemental and mineralogical composition analysis of the Andean snow is a worthwhile effort. In this study, we conducted a chemical composition analysis (major and trace elements, mineralogy, and chemical enrichment) of surface snow sampled at 21 sites across a transect of about 2,500 km in the Chilean Andes (18–41°S). Our results enabled us to identify five depositional environments: (i) sites 1–3 (in the Atacama Desert, 18–26°S) with relatively high concentrations of metals, high abundance of quartz and low presence of arsenates, (ii) sites 4–8 (in northern Chile, 29–32°S) with relatively high abundance of quartz and low presence of metals and arsenates, (iii) sites 9–12 (in central Chile, 33–35°S) with anthropogenic enrichment of metals, relatively high values of quartz and low abundance of arsenates, (iv) sites 13–14 (also in central Chile, 35–37°S) with relatively high values of quartz and low presence of metals and arsenates, and v) sites 15–21 (in southern Chile, 37–41°S) with relatively high abundance of arsenates and low presence of metals and quartz. We found significant anthropogenic enrichment at sites close to Santiago (a major city of 6 million inhabitants) and in the Atacama Desert (that hosts several major copper mines)