Polar Science最新文献

The article presents a two-dimensional three-layer non-stationary thermodynamic model allowing to calculate the annual variation (thermodynamic evolution) of the ice ridge using external meteorological and hydrological parameters as well as the information on the initial ice ridge porosity. For the test model simulation, the results of the study of morphometric characteristics of the ice ridge carried out in May-June 2011 and in April 2012 at « North Pole −38» and «North Pole −39» drifting stations were used. These studies were conducted using electric thermal drilling with computer recording of the penetration rate. Boreholes were drilled along the cross-section of the ridge crest at 0.5 m intervals. Cross-sectional profiles of ice ridge are illustrated. Applying the proposed model, it was possible to adequately reproduce the observed evolutionary changes in the main morphometric parameters (sail height, keel depth, thickness of the consolidated layer) of the investigated ice ridge.

This research note presents a report documenting a rare phenomenon observed in Sanionia uncinata (Hedw.) Loeske, entailing the presence of sporophytes across eight distinct locations on King George Island, Antarctica. Additionally, it briefly explores the potential correlation between regional warming air temperatures, water availability, and the emergence of these structures, suggesting their utility as indicators of climate change. Given that S. uncinata is recognized as a hygrophilic moss species typically found in well-hydrated environments, our hypothesis posits that the unprecedented development of substantial sporophyte numbers might be a consequence of rapid regional warming in the vicinity of the Antarctic Peninsula. Further investigations are essential to elucidate the potential interplay between shifting climate patterns and the observed proliferation of Sanionia uncinata sporophytes, thereby contributing to a more comprehensive understanding of their ecological responses to environmental fluctuations.

During geomagnetic quiet conditions, Indian Antarctic stations are considered to be located outside the auroral oval: Maitri (CGM coordinates: 63.3°S, 54.2°E) is equatorward and Bharati (CGM coordinates: 74.8°S, 98.4°E) is poleward of the auroral oval. Simultaneous observations of magnetic field variations at these two locations for 10-years (2013–2022) provide an opportunity to study quiet-time magnetic field patterns, if any. Geomagnetic quiet days with ΣKp ≤ 3 are selected, during which the lower values of solar wind and interplanetary parameters are also confirmed. Maitri station exhibits clear southern hemispheric solar quiet (Sq) type of magnetic field variation on geomagnetic quiet days in all seasons, indicating the influence of ionospheric dynamo due to thermospheric winds. Interestingly, Bharati station also displays regular and systematic magnetic field variations in all three components. The D-component at Bharati exhibits very strong variation at early morning hours (7–8 MLT), which is ∼2–4 times stronger than that of H-component, driving strong equatorward/northward currents during all seasons. Both stations show annual type of seasonal variation with peak amplitude during summer and least during winter. The schematic illustration of global and polar Sqs proposed here explains the results obtained through 10-years’ statistical study.

During the Austral summer of 2022, a study was conducted to investigate the physical properties of six lakes in the Larsemann Hills, East Antarctica. The lake water column's key properties, viz. temperature, salinity, density, fluorescence, and depth, were examined using a CTD profiler to establish a high-resolution description of their variations and identify the factors influencing intra and inter-lake variations. The results indicated that the shallow lakes LH14, LH04, and Discussion were well mixed. Lakes LH04 and LH14 on Stornes were affected by salinity, likely sea spray. In contrast, the deeper lakes, namely Nella, Cameron and Progress, were primarily driven by temperature and density dynamics. The hydrological characteristics of Cameron and Progress were notably impacted by their proximity to the ice sheet, while Nella was influenced by the presence of a partial lake ice cover. The lake depth, geographical location and presence of ice cover in the catchment significantly influenced temperature and salinity variations within the lakes. Deep lakes may be more sensitive to changes in temperature and density as compared to shallow lakes and could potentially affect other physical lake parameters. This baseline information is a valuable reference for future investigations on these lakes and similar environments.

The study includes ground-based data of surface mass balance calculations to assess the input of climate change on the ice sheet health. The study covers an approximately 471 km² area of the ice sheet that lies in between the Dålk and Polarårboken glaciers, Larsemann Hills, Prince Elizabeth, East Antarctica. Snow accumulation/ablation data is collected from 13 stake networks and 06 single stakes installed on the ice sheet. The monitored area is extrapolated on the basis of elevation and glaciological parameters using ArcGIS 10.8.1. The exposed height and precise locations of stakes have been recorded using DGPS and compared with the preceeding year's datasets. The annual measure accumulation/ablation data is processed in ArcGIS for the estimation of surface mass balance since 2018. The accumulation/ablation rate of the ice sheet is not uniform and influenced by the meteorological parameters i.e. temperature, precipitation and wind speed. The values of net surface mass balance are 0.027 Gt yr⁻¹, 0.088 Gt yr⁻¹, 0.044 Gt yr⁻¹, and 0.026 Gt yr⁻¹ since 2018 to 2021 respectively.

Geomorphometric modeling is widely used in geosciences. However, geomorphometric modeling and mapping of Antarctic oases has not been performed so far. This article presents the first results of our work on geomorphometric modeling and mapping of the Larsemann Hills obtained in the frameworks of the 68th Russian Antarctic Expedition in January–April 2023. As input data, we used a fragment of the Reference Elevation Model of Antarctica (REMA). From the extracted and edited digital elevation model, we derived digital models and maps of the following 17 morphometric variables: slope, aspect, horizontal curvature, vertical curvature, mean curvature, Gaussian curvature, minimal curvature, maximal curvature, unsphericity curvature, difference curvature, vertical excess curvature, horizontal excess curvature, ring curvature, accumulation curvature, catchment area, topographic index, and stream power index. We also conducted a field geomorphometric interpretation work to provide correct physical geographic, geological, and geomorphological interpretations of morphometric maps. In the fieldwork, we carried out 54 foot routes with the total length of about 422 km. During the routes, we collected 150 rock samples for further petrological and mineralogical analyses as well as three-dimensional modeling of the samples. Derived morphometric maps can be useful for structural geological and process-oriented hydrological studies. The ultimate goal of the ongoing work is to create a large-scale geomorphometric atlas of Antarctic oases and other ice-free Antarctic territories.

The lichen flora of coastal (Larsemann Hills, Landing Bluff, Rouer Islands) and internal (Clemence Massif, Radok Lake, Luff Nunatak, Stinear, Rymill and Bloomfield Mountains and others) oases (Princess Elizabeth Land and Mac Robertson Land, Antarctica) was investigated. 72 lichen species (incl. 48 species known for the Larsemann Hills) belonging to 34 genera and 14 families were recorded. Investigated species are listed and data on localities, habitats and frequency of occurrence are provided. The most common lichens in the area are Candelariella flava, Lecidea cancriformis, Lecanora fuscobrunnea, Buellia frigida, Rinodina olivaceobrunnea and Acarospora gwynnii.

Simultaneous observations of the atmospheric electric potential gradient (PG) at Bharati and Maitri stations were studied from 2014 to 2016. A new regional diurnal pattern of fair-weather PG for the coastal Antarctic region, perhaps the ubiquitous characteristics of the PG for the coastal Antarctic region, has been identified. This pattern has a significant broad minimum around noon hours. It is around this time the wind speed is also maximum. The PG data of past years of Syowa, Vostok, and Carnegie Cruise were also used in this study. The surface wind distorts the fair-weather diurnal pattern of PG over Bharati more intensely than at Maitri. The katabatic wind effect on the PG at Bharati appears to be more intense than at Maitri. The topography and katabatic winds associated with the Lambert glacier could be the reason. The observation of Bipolar Air Ion Concentration (BAIC) suggests that the wind speed significantly affects the concentration by accumulation and dispersion. The concentration is maximum when the wind speed is minimum. As the air ion concentration controls the conductivity, the PG is expected to be minimum during these hours to produce an anomalous diurnal pattern in the PG at Bharati. Data quality is improved by measuring the PG with a field monitor at the surface level instead of at an elevated position. This study provides new hope in pursuing globally representative data of the PG for further investigations on the global thunderstorm activity and the solar-terrestrial weather relationship.

Lichen communities are known to be most resistant and adapted organisms to the extreme environments; however, their abundance is not well mapped. Extensive lichen surveys were conducted as part of the 39th Indian scientific expedition and in-situ spectra (350 nm–2500 nm) of lichens were collected in the Larsemann Hills, East Antarctica during austral summer of 2020. Lichen abundance mapping was carried out with the help of Sentinel-2 MSI L2 data and surveyed records along with in-situ spectra. We generated feature collections for lichen, snow, water, bare surface and trained a random forest (RF) classification algorithms implemented in GEE and generated multi-class outputs. We finally merged all non-lichen classes and produced binary pixels with a confidence value (between 0 and 100) depicting similarity of its spectral response to that of a lichen pixel. Total 92 lichen points, 20 bare rock points, 26 points of water and 74 snow points were used to generate the probabilistic lichen abundance map. Resubstitution accuracy of 97.31% was obtained with 10 number of RF trees. Validation was done with geotagged ground photographs having 232 lichens, 20 bare rocks, 22 water and 69 snow points and achieved test accuracy of 82.44%.

Antarctica, the southernmost ice-covered continent, plays a pivotal role in unraveling Earth's intricate evolutionary processes. Several studies have been conducted to comprehend the crustal structure of West Antarctica. However, our understanding of the sub-surface structure in the East Antarctica region, particularly along Princess Elizabeth Land (PEL), remains limited due to the scarcity of geophysical data. To bridge this knowledge gap, we (NCESS) established a permanent broadband seismological observatory in the captivating region of Larsemann Hills, East Antarctica. In addition, we investigate the noise characteristics at the station, employing power spectral density (PSD) measurements. Results have been promising, indicating that the noise levels are within the range of New High Noise Model and New Low Noise Model. Monthly variations in PSD reveal different noise levels throughout the year, with winter months exhibiting lower levels of microseismic noise attributed to lower temperatures and frozen sea surfaces. The long-period noise is higher in April & May, possibly due to high-speed winds and lower in September & October. The outcomes serve as a testament to the success of our installation and ensure a valuable data set. The data will contribute to a comprehensive investigation of sub-surface structures in the PEL region of East Antarctica, enhancing our understanding of geological processes and tectonic evolution. Furthermore, the findings will serve as a valuable resource for future research and contribute to our knowledge of Earth's dynamic processes.