Polar Science最新文献

We report, in this work, the changes in the thermal structure of the mesosphere-lower thermosphere (MLT) region over an Indian Antarctic station Bharati (69.4° S, 76.2° E, CGM coordinates 75° S, 97° E) brought about by an intense geomagnetic storm of 23–24 March 2023 (Dst ∼ −155 nT). We use the temperature and OH airglow measurements of the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard NASA's Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission satellite to compare the thermal field of the MLT region on these disturbed days with the neighbouring quietest days of 27–28 March. Such comparison reveals both warming and cooling in the MLT region associated with the storm. An extension of this comparative study in the latitude region located poleward of Bharati also shows similar behavior of the MLT region during this geomagnetic storm. Overall, this study reveals the maximum temperature enhancement of ∼39–43 K to occur at around 99 km, a significant warming of ∼4–43 K in 95–105 km, and a decrease of ∼12–16 K in 80–87 km. While the enhancement of temperature in 95–105 km appears to be a consequence of the auroral heating associated with this storm; we are unable to account for the cooling below based on existing theories. Present observation of the development of cooling underneath the region of temperature enhancement during the geomagnetic storm is rare and demands further investigation.

The National Remote Sensing Centre (NRSC) has established its ground station named Antarctica Ground Station for Earth Observation Satellites (AGEOS) at Bharati station located at Larsemann hills area of Antarctica for the tracking and data acquisition from polar orbiting satellites. A communication link through a geostationary satellite in C-band is being used for transferring data to the mainland. There is a need to enhance the data rate in the near future considering the huge volume of data being acquired at AGEOS. A satellite link operating at Ka-band is proposed for accommodating the bandwidth requirements. It is necessary to estimate the worst case atmospheric attenuation at Ka-band over Larsemann hills area for calculating the link margins required. The India Meteorological Department (IMD) has setup a wide range of meteorological instruments at Bharati station and the local data collected for the years 2020, 2021 and 2022 are used in this study. The link is assumed to operate at a frequency of 20 GHz with linear polarization. An exceedance probability of 0.1% is used to arrive at the annual statistics of the attenuation. Recommendations by the International Telecommunication Union (ITU) are followed and the estimation is carried out using MATLAB. An estimated total atmospheric attenuation of 2.28 dB is obtained. The results are used further for carrying out link budgeting for a Ka-band satellite communication link between Bharati station and India.

Supraglacial discharge of limiting micronutrients such as iron (Fe) into high-nutrient low-chlorophyll (HNLC) regions like the Southern Ocean has recently drawn global attention. In this study, we aim to understand the contribution of cryoconite holes (comprising a meltwater column with an underlying layer of sediment) to the discharge of Fe through the glacier runoff. Cryoconite hole meltwater collected from the Larsemann Hills, East Antarctica showed a higher concentration of dissolved Fe (dFe: 71.2 μgL⁻¹) and total Fe extractable from suspended sediments (exFe: 362.1 μgL⁻¹) than in the adjacent streams (dFe: 30.5 μgL⁻¹; exFe: 21.2 μgL⁻¹) and melt pools (dFe: 42.3 μgL⁻¹; exFe: 5.8 μgL⁻¹). Predictive pathways (using PICRUSt2) show that cryoconite hole bacterial communities could acquire Fe and other trace elements using different mechanisms, such as the biosynthesis of siderophores, and transport proteins, therefore influencing the trace metal chemistry in these and other environments that drain cryoconite hole contents. Estimated discharge of dFe (11.4 kg km⁻² a⁻¹) and exFe (57.9 kg km⁻² a⁻¹) within cryoconite holes are 2 and 17 times higher, respectively than the discharge from the adjacent supraglacial streams, indicating that cryoconite holes are an important source of potentially bioavailable Fe to the HNLC region.

Study on the measurement of background radiation level in and around Bharati station, Larsemann Hills region of East Antarctica was taken up using different types of detectors. The radiation levels due to cosmogenic (especially neutron) and terrestrial origin (gamma and neutron) and natural radioactivity due to presence of primordial radionuclide in the samples of soil, rock, lake water, ice and air were measured. The data on radionuclide activities of soil and lake water are presented pictorially using surfer plot. The study was further extended to the in-situ measurement of Radon/Thoron concentration in soil pores. Measurement of gross alpha and beta activity in air samples was also carried out. These studies were conducted during several Indian Scientific Expeditions to Antarctica (ISEA) (32^nd to 36^th) for the period from 2012 to 2017. Some of the data generated during the above mentioned expeditions are already published previously and hence mentioned very briefly in the text whereas the unpublished data are presented and discussed in this article for the first time.

The untouched condition of Antarctica's environment is a result of its inherent absence of human activity. Nevertheless, with the introduction of scientific research stations and human presence, a considerable volume of wastewater has been produced by these research facilities. The wastewater needs to be treated before discharge and has strict rules and regulations set by the Antarctic Treaty (Annexure III). However, the performance of the wastewater treatment plant and the data on the quality of the effluents being discharged into the sea by different stations are limited. In this study, the performance of the wastewater treatment plant at Bharati research station located at Larsemann Hills, East Antarctica was investigated from 2015 to 2022. Physical and chemical parameters such as pH, EC, NH₄–N and COD were determined in effluents from the drinking water plant, blackwater and greywater plant from Bharati station. The pH and EC of the effluents were measured using portable probes, ammonia was measured spectrophotometrically, and COD was measured using the closed reflux digestion method. The monthly data of the effluents from 2015 to 2022 for pH, EC, NH₄–N and COD indicate values within the permissible limits except for a few parameters at a certain time frame. It was observed that the pH of black, grey and drinking water varied between pH 6.5 and 9.1. Both grey and blackwater showed a decreasing conductivity trend, suggesting decreased ionic content. The blackwater exhibited an increase in ammonia concentration and COD trend, indicating higher organic pollution levels, while the grey water displayed a decreasing trend in COD, indicating a reduction in organic matter content. The study also investigated the correlation between NH₄–N concentration in wastewater and greywater with levels of COD and compared these levels with standard values to assess effluent water quality. The data will provide baseline values to assess any malfunctioning of the wastewater system in treating the contaminants. Effluent data from other Antarctic stations show a high value compared with the effluents from Bharati station. Such variability largely depends on the station size, water usage and number of expedition members during the summer and winter seasons.

Antarctica serves as an ideal prototype to study past climatic condition as the ice core records dates back to 100,000 years. Microbiological research on ice core has opened a doorway to our understanding on biodiversity and its contribution to the frozen ecosystem. In this review, the ice core bacterial diversity of East and West Antarctica has been documented. Cold-adapted bacteria hold immense potential in biotechnological applications as they possess functional advantages over mesophilic bacteria. Some of the neoteric applications of bioproducts of Antarctic bacteria have been stated in this review. The current climate change due to global warming exerts a humongous effect on the ecosystem of the polar region. The region being susceptible to any fluctuation in temperature, the exacerbated melting of Antarctic glaciated mass contributes to the rise of global sea level, with loss of ice harbouring unknown microbial entities. This review mainly focuses on the bacterial diversity of East and West Antarctic counterparts, the prevalence of antibiotic-resistant genes, the adaption strategies conferred by bacteria thriving in Antarctic habitats and their potential biotechnological applications.

Phytoplankton, the primary producers of all aquatic systems, form the base of the marine food web. Any change in the environmental settings of the given ecosystem will affect the phytoplankton community structure of the region. In the present work, water sampling was carried out from the poorly explored polar region, beneath the sea ice during the melting phase of land-fast ice near Indian Antarctic Research Station Bharati in Prydz Bay, East Antarctica. The water samples were analyzed for phytoplankton species diversity, nutrients, temperature, salinity, and Chlorophyll a (Chl a). Our observations indicate marked variations in phytoplankton biomass and community. A shift from diatom (Thalassiosira sp., Fragilariopsis sp.) to dinoflagellate (Protoperidinium sp.) community, along with the emergence of grazers was seen by the end of the observation period. The background environmental conditions also showed marked variations, as the concentration of nitrate at 0m depth reduced from 31.8 μM at Obs-1 to a non-detectable limit at Obs-3. Furthermore, at 0m depth, temperature increased from −1.32 °C at Obs-1 to −0.38 °C at Obs-3 while salinity decreased from 34.11 at Obs-1 to 33.68 at Obs-3, thus indicating the melting phase of sea ice from Obs-1 to Obs-3. These observations showed vertical stratification resulting from the basal melting of land-fast sea ice resulted in better availability of light, phytoplankton community change due to nutrient availability/utilization/limitation, followed by the presence of grazer community. This preliminary understanding will serve as a baseline dataset to design the targeted sampling/experiments in the future from the land-fast ice ecosystem.

The Rauer Group and Vestfold Hills are critical components of the East Antarctic Shield and are believed to have been parts of the supercontinents Rodinia and Gondwana. The Rauer Group is characterized by Archean to Pan-African thermal history, while the Pan-African signature in the Vestfold Hills is restricted to its southwestern margin. The correlation between the Rauer Group and Vestfold Hills remains controversial, while the significance of amalgamation between these two terranes remains unclear. Most importantly, the precise nature and timing of the Rauer-Vestfold contact is disputed. In this review, we compare the available structural, metamorphic, geochronological and geophysical data in these two East Antarctic terranes and suggest that (i) the Rauer Group and Vestfold Hills of East Antarctica were amalgamated during the late Mesoproterozoic to early Neoproterozoic (∼1000 Ma), and (ii) the Rauer-Vestfold contact is located beneath the Sørsdal Glacier in the East Antarctic Shield. Finally, we argue that juxtaposition of the Rauer-Vestfold contiguous crustal unit with the Eastern Ghats Province (EGP)-Rayner amalgam took place in the Pan-African time (∼500 Ma).

This study presents a mathematical model of heat and mass transfer for modelling the formation and evolution of taliks in the upper subsurface of the Larsemann Hills in East Antarctica. Four simulation scenarios were considered. The first one showed that thawed areas cannot form under snowfields. The second and third scenarios demonstrated the taliks did not form if the snow melted immediately after set the positive air temperatures and covered the surface 20 days before the set of negative air temperatures or immediately after that. According to the last scenario, talik forms when snow cover persists even with positive air temperature, and snow falls before the air temperature becomes negative. Modelling demonstrates that taliks in the Larsemann Hills exist, but they are mostly in an unstable state.

Antarctica contains 90% of the Earth's ice; if it melts, it can significantly contribute to the rise in global sea levels. Over Antarctica, short-term atmospheric warming events have led to significant surface melt in summer. Understanding the conditions of such warming events and subsequent surface melt is highly prioritized in Polar Research. The austral summer of 2016-17 witnessed the largest melt duration of the 21^st century over Ingrid Christensen Coast (ICC), East Antarctica. Being situated on the grounded ice near four research stations, understanding the melt over the region has both scientific and operational importance. Here, we investigate the drivers of four major melt events identified over ICC for the austral summer of 2016-17 using the reanalysis dataset, ERA5. The first melt event, coinciding with the season's highest air temperature, was triggered by high turbulent heat flux from strong katabatic winds, while the rest of the events were triggered by low-level, liquid cloud-induced longwave radiation. During the melt events, anomalous high pressure ridges were present over the continent causing low pressure systems to remain stationary for an extended period and direct warm, moist air towards the ICC, facilitating melting. The present study observed melting occurring above the grounding zone, and if such melting extends to a larger scale beyond ice shelves, it could raise significant concerns regarding the hydrodynamics and stability of ice sheets in the future.