Polar Science最新文献

In the Larsemann Hills, three countries – Russia, China, and India – maintain year-round stations, while Australia operates a summer facility. These countries engage in diverse scientific research in the Larsemann Hills and the surrounding areas. The unprecedented cooperation resulted in the International Conference on Antarctic Research (ICAR) at Bharati station in 2020. Additionally, the BRICS working group on ocean and polar science and technology (OPST) has played a crucial role in fostering scientific engagements. This first volume of the special issue compiles twenty-five research findings based on data collected in the region, including presentations from ICAR-2020. Beyond showcasing international cooperation, the special issue also commemorates a decade of the Bharati station’s presence in the Larsemann Hills.

The total electron content (TEC) is a key parameter that is used to understand the effects of ionosphere on satellite-based navigation and communication signals. The ionosphere at polar is highly dynamic and acts as a major sink for the solar-terrestrial energy transfer processes, different magnetospheric and space weather events. Especially in Antarctica, the observation is still sparse due to a limited number of stations. In this paper, the study of ionosphere variability over Bharati station (69.41° S, 76.19° E), an Indian Antarctic research base at Larsemann Hills, was carried out. During the geomagnetically quiet conditions, the Bharati station is located outside of auroral oval but towards the poleward of auroral oval. The variation of ionosphere for diurnal, seasonal, and solar activity was studied using the TEC data for the years 2010–2022 which covers the solar cycle 24. The TEC diurnal pattern is strong even during polar days and nights with a peak at local noon. The seasonal variability was distinctly observed with about 50% increase in TEC during equinoctial months compared to summer months during high solar active year 2014. However, during low solar active year there is a marginal increase of TEC in equinoxes compared to summer.

Antarctica, the southernmost continent on Earth, is a harsh and remote place with an extreme climate. Despite its challenges, the continent has become a significant site for scientific research, particularly in the fields of earth sciences, glaciology, environmental science, atmospheric sciences, meteorology, palaeoclimatology, and biology. As a signatory to the Antarctic Treaty, India has actively pursued scientific research on the continent since 1981. The Indian Antarctic Program has conducted research, provided logistical support, and monitored environmental activities in Antarctica for over four decades. Science is a currency in Antarctica, and international collaboration is the route to progress. This article explores India's efforts, particularly those of the Ministry of Earth Sciences, Government of India, and the National Centre for Polar and Ocean Research, in fostering international collaboration in Antarctica.

Antarctica harbours a wide range of extreme and diverse ecological niches that support diverse group of microorganisms, making it important to investigate the microbial diversity of this pristine environment. The current study focuses on the diversity and distribution of fungi in diverse environmental niches like exposed soil, accumulated snow, deep sea, and lake sediments in the Larsemann Hills, Antarctica. Ascomycota (61.7%) was the most dominating phylum followed by Basidiomycota (31.1%), Chytridiomycota (5.7%) and Rozellomycota (1.4%). The families Camptobasidiaceae (23.1%), Cladosporiaceae (15.3%), Kriegeriaceae (8.2%), Mycosphaerellaceae (6.8%) and Helotiaceae (6.2%), while at the genus level Glaciozyma (24.8%), Cladosporium (16.8%), Phenoliferia (8.8%), Acrodontium (8%), and Aspergillus (5.4%) were highly prevalent. Interestingly, Austroplaca genus which is mostly indigenous to polar regions was exclusively detected in the accumulated snow sediments. Among the four heterogenous environments analyzed, lake sediments were shown to have a higher number of amplicon sequence variants (ASVs) than the other environments.

Surface roughness is an important parameter in deriving energy balance over the polar ice-sheets and glaciers. In Antarctica, roughness appears as snow patches and is affected by wind transport. It is also influenced by snowfall, snowdrifts, snowmelt, and snow grain size. In this paper, we derive surface roughness using a laser distometer. The roughness measurements were collected during the 32nd Indian Scientific Expedition to Antarctica 2013 (ISEA-32). After removal of all the possible error sources, it is found that around the Indian Antarctic station Bharati (69.41°S, 76.18°E), roughness is in the range of 0.7–1.2 cm. Snowfall and wind introduce fluctuations in surface roughness measurements. Measurements around Maitri (70.76°S, 11.73°E) showed that different ice surfaces have different values of roughness (0.6–1.4 cm), with the minimum roughness in the interior ice sheet surrounded by hummocks. Sastrugi patterns were also captured in the analysis. Backscattering signatures from RADARSAT-2 imagery were examined in conjunction with the roughness measurements.

The Vestfold Hills sector on the coastal fringe of the Princess Elizabeth Land forms part of an Archean to Paleoproterozoic aged cratonic nucleus of the East Antarctic Shield. A charnockite-granite association from the Mossel Gneiss Group in the northern region of the Vestfold Hills is investigated in this work to characterise the metamorphic-magmatic evolution of the area. Conventional thermometry and phase equilibria modelling indicate that the charnockite formed as a result of ultra-high temperature metamorphism at low-intermediate pressure (∼4 kbar). Phase equilibria modelling, reveals that the melt-integrated charnockite composition is a restitic product of a protolith of quartz diorite composition which underwent isobaric heating (peak temperature up to 960 °C) at 4 kbar pressure followed by anatexis. The anatexis of the quartz diorite protolith also resulted in the formation of the associated granitic melt. U–Th-Pb_Total ages obtained from monazites of the granite integrated with CHIME ages extracted using the isochron method indicate an emplacement age of ∼2200 Ma and two younger events are recorded at ∼2000 Ma and ∼1700 Ma. The younger ages are ascribed to the resetting during the emplacement of younger basalt dykes that cross cut the charnockite-granite sequence. Vestfold Hills’ geological correlations with Indian and Australian cratons are discussed considering this new data.

The study focuses on the current state of englacial Lake Dålk (Larsemann Hills Oasis), which was completely devastated in January 2017 by a catastrophic outburst and formed again in February 2020. A set of works including ground-penetrating radar (GPR) profiling, geodetic survey, core drilling, thermometric measurements and isotopic analysis was performed. As a result, new data were obtained about the modern boundaries of the reservoir, ice thickness and depths, as well as about the peculiarities of freezing of the lake after re-formation. Based on the field data obtained, one-dimensional mathematical modeling of Lake Dålk freezing was carried out, the results of which showed further scenarios of its evolution.

The present study reports on the variability of atmospheric carbon dioxide (CO₂) and methane (CH₄) concentrations over Antarctica using data collected during the 2015–2016 and 2016–2017 as part of the Indian Scientific Expedition to Antarctica (ISEA). During the austral summer (January–March), this study examined the spatio-temporal variability in atmospheric CO₂ and CH₄ concentrations at the Indian Antarctic Stations (IAS). An average atmospheric CO₂ concentration was observed to be 396.25 ± 4.20 ppm at Bharati station during 2015-16 austral summer period, whereas CO₂ (CH₄) concentrations were 398.7 ± 0.46 ppm (1780 ± 2 ppb) and 399.1 ± 0.41 ppm (1780 ± 3 ppb) at Bharati and Maitri stations, respectively during 2016–17. During the study period, the Orbiting Carbon Observatory-2 (OCO-2) based column averaged CO₂ concentration shows similar values against records. At Bharati and Maitri, the diurnal amplitudes of CO₂ (CH₄) are varied from 0.11 ppm (0.37 ppb) to 8.90 ppm (11.44 ppb) and 0.54 ppm (1.96 ppb) to 7.30 ppm (16 ppb), respectively. In the austral summer, dominant winds at the IAS are from the east, northeast, and southeast.

Climate variability is thought to have an impact on the Ronne Ice Shelf (RIS), one of the largest ice shelf in Antarctica, located at the mouth of the Weddell Sea. However, investigations evaluating the impact of climate variability on the geometry (front edge) of this ice body have not yet been done. This study examines a spatial-temporal shift in the front edge of the Ronne Ice Shelf during the years 2004–2019 using an integrated approach based on remote sensing and climate data. The Moderate Resolution Imaging Spectro-radiometer (MODIS) satellite images have been used to study the changes in the ice shelf along transects drawn at a constant interval of 5 km throughout the 16-year period over the second half of the austral summer months (February to March). The study reveals that there has been net progradation of ∼20 km in the front edge of the ice shelf in the sector 2 between 2004 and 2019. This progradation in the ice shelf may be attributed to draining of upper ice streams to the RIS and the decrease in temperature. Thus, the present study establishes how a combination of the use of satellite imagery and statistics can effectively be used to comprehend and quantify changes in the variability of the front edge of the ice shelf.

Concentrations and isotopic compositions of noble gases (He, Ne, Ar, Kr, and Xe) and nitrogen in two ordinary chondrites (OCs), Zag (H3-6) and ALH 77216 (L3.7–3.9), are presented. The aim of the study is to examine the cosmic ray exposure history, radiogenic ages and isotopic signatures of trapped gases in them. The results of stepwise heating analyses indicate that light noble gases (He and Ne) are mixture of trapped and cosmic ray produced components. Neon isotopes are enriched from solar wind (SW), while shows a trend towards galactic cosmic ray (GCR) region in both the meteorites. Phase-Q neon is not observed in any of the meteorite. The heavy noble gases Ar, Kr and Xe indicate mixture of Q-HL-SW and cosmogenic. Elemental ratios of trapped ³⁶Ar, ⁸⁴Kr and ¹³²Xe indicate that noble gases in Zag and ALH 77216 are mixtures of the three components Q, HL and SW. The cosmic-ray exposure (CRE) ages calculated from neon for Zag and ALH 77216 are 5.6 ± 0.3 Ma and 28.5 ± 0.4 Ma, respectively. These ages are within the range typically observed for the respective meteorite types of OCs. Nitrogen isotopes indicate presence of multiple components in both the chondrites. Isotopic signature of trapped nitrogen in both the chondrites is distinct from that of SW, Q and HL, indicating additional source of nitrogen in the meteorites.