Physical properties of shallow ice cores from Antarctic and sub-Antarctic islands

The sub-Antarctic is one of the most data-sparse regions on earth. A number of glaciated Antarctic and sub-Antarctic islands have the potential to provide unique ice core records of past climate, atmospheric circulation, and sea ice. However, very little is known about the glaciology of these remote islands or their vulnerability to warming atmospheric temperature. Here we present melt histories and density profiles from shallow ice (firn) cores (14 to 24 m) drilled on three sub-Antarctic islands and two Antarctic coastal domes. Additionally, complementary ground-penetrating radar (GPR) data were collected to further characterize each site and assess the spatial distribution of the observed melt layers. This study includes the first ever firn cores from Bouvet Island (54∘25′19′′ S, 03∘23′27′′ E) in the South Atlantic, from Peter I Island (68∘51′05′′ S, 90∘30′35′′ W) in the Bellingshausen Sea, and from Young Island (66∘31′44′′ S, 162∘33′21′′ E) in the Ross Sea sector's Balleny island chain. Despite their sub-Antarctic location, surface melt is low at most sites (melt layers account for ∼ 10 % of total core), with undisturbed ice layers in the upper ∼ 40 m, suggesting minimal impact of meltwater percolation. The exception is Young Island, where melt layers account for 47 % of the firn core. Surface snow densities range from 0.47 to 0.52 kg m−3, with close-off depths ranging from 21 to 51 m. Based on the measured density, we estimate that the bottom ages of a 100 m ice core drilled on Peter 1 Island would reach ∼ 1856 CE and ∼ 1874 CE at Young Island

Subglacial lakes and hydrology across the Ellsworth Subglacial Highlands, West Antarctica

Subglacial water plays an important role in ice sheet dynamics and stability. Subglacial lakes are often located at the onset of ice streams and have been hypothesised to enhance ice flow downstream by lubricating the ice–bed interface. The most recent subglacial-lake inventory of Antarctica mapped nearly 400 lakes, of which ∼ 14 % are found in West Antarctica. Despite the potential importance of subglacial water for ice dynamics, there is a lack of detailed subglacial-water characterisation in West Antarctica. Using radio-echo sounding data, we analyse the ice–bed interface to detect subglacial lakes. We report 33 previously uncharted subglacial lakes and present a systematic analysis of their physical properties. This represents a ∼ 40 % increase in subglacial lakes in West Antarctica. Additionally, a new digital elevation model of basal topography of the Ellsworth Subglacial Highlands was built and used to create a hydropotential model to simulate the subglacial hydrological network. This allows us to characterise basal hydrology, determine subglacial water catchments and assess their connectivity. We show that the simulated subglacial hydrological catchments of the Rutford Ice Stream, Pine Island Glacier and Thwaites Glacier do not correspond to their ice surface catchments

Ice thickness observations in Glacier Schiaparelli, Cordillera Darwin, Chile

This dataset represents the first ice thickness measurements at Glacier Schiaparelli in Cordillera Darwin, Southern Chile. Data were collected in April 2016 using a ground-penetrating radar (http://www.unmannedindustrial.com/sites/default/files/GPR.pdf) in the ablation area of the glacier. The ASCII file contains 5 columns with the geographical position, elevation and ice thickness interpreted from the radar data. The coordinates (WGS84/UTM 19S) were recorded using a navigator which is integrated to the radar system. The field campaign and the measurements were part of CONICYT-BMBF project GABY-VASA "Responses of Glaciers, Biosphere and Hydrology to Climate Variability across the Southern Andes"

High resolution stable water isotope composition (δ¹⁸O and dD) of two firn cores at the northern Antarctic Peninsula

The Antarctic Peninsula is one of the most challenging regions of Antarctica from a climatological perspective, owing to the recent atmospheric and oceanic warming. The steep topography and a lack of long-term and in situ meteorological observations complicate extrapolation of existing climate models to the sub-regional scale. Here, we present new evidence from the northern Antarctic Peninsula to demonstrate how stable water isotopes of firn cores and recent precipitation samples can reveal climatic processes related to nearby oceanic and atmospheric conditions. A noticeable effect of the sea ice cover on local temperatures and atmospheric modes, in particular the Southern Annular Mode (SAM), is demonstrated. In years with 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 valid for all seasons cannot be concluded. The delta-T relationship rather depends on seasonal variability of oceanic conditions. Transitional seasons (autumn and spring) are both stable seasons with an isotope-temperature gradient of +0.69 per mil/°C. The firn stable isotope composition reveals that the near-surface temperature at the Antarctic Peninsula shows a decreasing trend (-0.33 °C/y) between 2008 and 2014. Moreover, the deuterium excess (d excess) has been demonstrated to be a reliable indicator of seasonal oceanic conditions, and therefore suitable to improve a firn age model based on seasonal d excess variability. The annual accumulation rate in this region is highly variable, ranging between 1060 kg/m**2/y and 2470 kg/m**2/y from 2008 to 2014. The combination of isotopic and meteorological data is key for reconstructing recent climatic conditions with a high temporal resolution in polar regions where no direct observation exists

Ice thickness measurements in Chile using radio echo sounding

El radio eco sondaje ha sido una de las técnicas más utilizadas en los últimos años para medir el espesor de hielo en glaciares a lo largo de prácticamente todo Chile, especialmente en la región Central y en los Campos de Hielo Patagónicos. En este trabajo se presentan los principales sistemas utilizados en las últimas décadas y los resultados más representativos obtenidos con un sistema aerotransportado de reciente desarrollo que usa antenas de dipolo tipo bow-tie de frecuencias entre 20 y 50 MHz, las que son transportadas con helicóptero. Este sistema fue probado en glaciares hasta ahora inaccesibles o medidos a pie en perfiles que no han sido representativos de la totalidad del hielo prospectado. En estos glaciares, el sistema aerotransportado obtuvo una gran cobertura de datos gracias a sus ventajas operacionales de medir zonas con fuertes pendientes y sus capacidades de diseño electrónico, gracias a lo cual se logró detectar la estructura interna del hielo y la totalidad del espesor allí existente. Entre los resultados obtenidos destaca el espesor máximo de 129 m medido en el Glaciar Olivares Alfa (33°11’ S /70°13’ O) de 3.91 km2 de superficie en el año 2013, donde la gran cantidad de líneas levantadas permitió determinar un volumen equivalente de agua de 0.17 ± 0.02 km3.Radio echo sounding has been one of the most utilized techniques in Chile in recent years for measuring ice thickness, particularly for glaciers in the central Chilean Andes and in the Patagonian Ice Fields. In this article, the main surveying systems and the most representative results are presented. A helicopter-borne system, consisting of bow-tie dipole antennas with frequencies between 20 to 50 MHz, was successfully tested at several glaciers that had previously been poorly studied due to their difficult and remote terrain. For these glaciers, the operational performance and electronic design of the system proved appropriate for detecting internal ice structures and ice thicknesses. Surveys carried out at Glaciar Olivares Alfa (33°11’ S, 70°13’ W, 3.91 km2 in 2013), for example, obtained a maximum ice thickness of 129 m. Survey density at this glacier allowed determination of ice volume equating to 0.17 ± 0.02 km3 w.e.Asociación Argentina de Geofísicos y Geodesta

The first firn core from Peter 1st Island – capturing climate variability across the Bellingshausen Sea

Peter 1st Island is situated in the Bellingshausen Sea, a region that has experienced considerable climate change in recent decades. Warming sea surface temperatures and reduced sea ice cover have been accompanied by warming surface air temperature, increased snowfall, and accelerated mass loss over the adjacent ice sheet. Here we present data from the first firn core drilled on Peter 1st Island, spanning the period 2001–2017 CE. The stable water isotope data capture regional changes in surface air temperature, and precipitation (snow accumulation) at the site, which are highly correlated with the surrounding Amundsen-Bellingshausen Seas, and the adjacent Antarctic Peninsula (r>0.6, p<0.05). The unique in-situ data from an automatic weather station, together with the firn core data, confirms the high skill of the ERA5 reanalysis in capturing daily mean temperature and inter-annual precipitation variability, even over a small Sub-Antarctic Island. This study demonstrates the suitability of Peter 1st Island for future deep ice core drilling, with the potential to provide an invaluable archive to explore ice-ocean-atmosphere interactions over decadal to centennial timescales for this dynamic region