Polar Science最新文献

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.

Bromine chemistry plays an important role in tropospheric ozone depletion events in polar regions. Autocatalytic reactions lead to bromine explosion events, causing ozone depletion to near-zero levels in the polar troposphere. Bromine chemistry over Antarctica is not fully understood, and ground-based observations are scarce. This work presents year-long observations of bromine oxide (BrO) over the Bharati station (69.41°S, 76.19°E) using Multi-axis Differential Optical Absorption Spectroscopy (MAX-DOAS) from December 2018 to February 2020. The results show that elevated BrO mixing ratios were found during spring (September), with a maximum value of 10.21 ± 4.38 pptv for clear sky conditions and 33.15 ± 2.23 pptv for cloudy conditions. BrO was not observed above the detection limit (∼3 × 10¹³ molecule cm⁻²) outside spring on clear days. In general, lower mixing ratios were observed on clear days over Bharati compared to stations in West Antarctica. This indicates a different source strength over East Antarctica compared to West Antarctica. BrO vertical column densities were high during spring, with a maximum value of 1.34 ± 0.35 × 10¹⁴ molecule cm⁻². The vertical profiles of the BrO mixing ratios show a peak at the surface during spring (average of 6.5 ± 1.91 pptv), decreasing sharply with altitude. Back trajectories show that air masses passing over the first year ice showed higher BrO, although factors such as meteorology play an important role in determining the absolute levels. Using a box model, we show that bromine chemistry can deplete as much as 2.15 ppb of ozone in a day at the Bharati Station on clear days, which shows that it does not lead to complete ozone depletion events over Bharati.

Columnar aerosol loading and surface level atmospheric black carbon (BC) concentration over the Antarctic are examined using the measurements carried out at the Indian Antarctic stations, Bharati and Maitri, as part of the 36th Indian Scientific Expedition (2016–17) to Antarctica (ISEA). The mean aerosol optical depth (AOD) at wavelength 500 nm at Bharati is observed to be 0.101 ± 0.01, whereas that at Maitri is 0.047 ± 0.003. Columnar aerosol loading at Bharati is found to be more than two times that measured at Maitri. The daily mean surface level atmospheric BC concentration at Bharati in the Austral summer from December 2016 to February 2017 is 24 ± 16.5 ngm⁻³. Comparison of this measurement with earlier reported values over the same region indicates an increase in surface-level atmospheric BC concentration. Long-term (1997–2017) trend analysis carried out using MERRA-2 aerosol reanalysis data also corroborates the increasing trend in AOD and BC concentration with 0.005 (0.007) yr⁻¹ and 0.3 (0.27) ngm⁻³ yr⁻¹ over Bharati (Maitri) respectively. Spectral variations of aerosol absorption coefficients show absorption angstrom exponent values (AAE) close to unity (1.096 ± 0.029), which indicates that fossil fuel emission is the primary source of absorbing aerosols over this region. During the study period, air mass back trajectory analysis indicates that the sources are from the Antarctic, coastal, and southern ocean regions with no long-range transport from other continents in the southern hemisphere.

This study presents the mineral magnetic, particle size, and organic content data of surface soils from Larsemann Hills, East Antarctica. The analysis of isothermal remanent magnetization and the high specific magnetic susceptibility values –mean (±S.D.) values of 117.7 (±175.0) × 10⁻⁸m³kg⁻¹ for Broknes Peninsula and of 330.9 (±217.4) × 10⁻⁸m³kg⁻¹ for Grovnes Peninsula– indicate high concentrations of low-coercivity magnetic minerals. The magnetic minerals are coarse-grained in the multidomain and pseudo-single domain range, and the significant correlation between some magnetic parameters suggests the dominant control of multidomain grains. The remanent acquisition coercivity H_1/2 shows mean (±S.D.) values of 38.2 (±4.9) for Broknes and 38.3 (±3.7) mT for Grovnes soils suggesting magnetite dominance. The soils lie in the sand and loamy sand textural classes, and the concentration of organic matter is very low. Values of percentage frequency-dependent susceptibility indicate insignificant proportions of superparamagnetic grains, and therefore no significant evidence for pedogenic magnetic minerals was observed in these soils. The magnetic signal of Larsemann Hills soils was primarily terrigenous with no contributions from bacterial magnetite, authigenic greigite and anthropogenic magnetic minerals.

In this paper, we present new data on the structure of the basin of Progress Lake (Larsemann Hills, East Antarctica). Located close to major logistic facilities of the polar stations and known for regular outburst floods, this lake was an object of interest in terms of ensuring safety of logistics operations. First reconnaissance survey carried out to the west of the known boarder of the Progress Lake showed the presence of a subglacial cavity filled with water. Based on the results of detailed ground-penetrating radar survey, electro-thermal drilling, water level observations, echo-sounding survey, and underwater photography, we show that this cavity acts as a subglacial part of the Progress Lake. We present the main morphometrical characteristics of Progress Lake calculated according to the new data: total area (203 600 m²), volume (1 806 300 m³), average depth (8.9 m), maximum depth (42.3 m), length (1160 m), maximum width (330 m). We also present an updated map of the Progress Lake and hydrological data (water level changes, water temperature, salinity, ion composition). The presence of perennial ice cover above the western part of the lake basin is explained by the specific microclimatic conditions of the area.