Arctic and Antarctic Research Institute

Abstract. While air bubbles in polar ice cores are well known for archiving past atmospheric composition, the quantity of air trapped in these bubbles also carries significant paleoclimatic information. This parameter, known as Total Air Content (TAC), was first used to reconstruct past ice sheet elevation and later became an orbital dating tool after its temporal variations revealed a strong correlation with local summer insolation. However, limited understanding of relationships between TAC, pore volume at close-off depth, and surface parameters has restricted its widespread use. In this study, we investigate the link between surface parameters (e.g. temperature and accumulation) and changes in TAC at both spatial and temporal scales in order to better understand TAC as an environmental proxy and as an orbital dating tool. To do so, we first present a new dataset extending the TAC record from the EPICA Dome C (EDC) ice core back to 800 ka, as well as new TAC records from the TALDICE and EDML ice cores covering the last glacial-interglacial cycle. Second, we combine these new datasets with a compilation of published TAC data from ice cores across Antarctica and Greenland to explore the influence of surface climate parameters controlling the changes in TAC both at spatial and temporal scales. Our spatial-scale analysis first examines how recent TAC values relate to atmospheric pressure and elevation. We then investigate pore volume at close-off (i.e. TAC values corrected for ideal gas law effects) to assess the influence of mean annual temperature, accumulation rate, and local summer insolation. We evidence a strong correlation between the pore volume at close-off and local half year summer insolation for East Antarctic sites, suggesting a direct control of local insolation on firn densification in this region. Temporal-scale analyses on TAC records covering at least 40 ka confirm that TAC records contain an orbital-scale signature of local insolation but also show that local summer insolation alone cannot capture the full TAC variability. Multiple regression analysis incorporating local insolation and reconstructed surface temperatures or accumulation better predicts TAC temporal changes, particularly during glacial terminations. Our new EDC high-resolution record also revealed significant millennial-scale TAC changes during these glacial terminations. Hence, our results highlight that in addition to the orbital-scale impact of local summer insolation, millennial-to-multi-millennial-scale changes in surface climate parameters also influence the temporal-scale TAC changes. Our findings suggest that orbital tuning between TAC and local insolation that neglects surface climate controls could introduce age uncertainties of 1–5 ka, calling for surface climate-related corrections prior to TAC-based orbital dating.

During the North Pole–41 expedition, three components of the VLF electromagnetic field were simultaneously measured on a drifting ice-resistant platform and at the Lovozero and Barentsburg observatories. We consider three VLF events that occurred in magnetically quiet time. During two of them (the events on January 24, 2023 and March 12, 2024), auroral hiss bursts were recorded at three stations located in the auroral and circumpolar regions and spaced up to 2.600 km apart. The spectral and temporal characteristics of the bursts at all the stations were almost the same. The fact that hiss was recorded with the same properties at such large distances can be explained under the assumption of a homogeneous flow of auroral electrons with energies from 0.1 to 10 keV throughout the precipitation area, which generate quasi-electrostatic waves at altitudes 10–20 thousand km, along with the simultaneous presence of small-scale ionospheric irregularities in the vicinity of all three stations, where these waves are scattered into the propagation cone to the Earth surface. We examine the case of hiss recording (the January 25, 2023 event) demonstrating the locality of the hiss recording area during one day — a hiss burst is first observed at one station, then at another. This is probably due to the appearance/disappearance of local areas of small-scale irregularities, where quasi-electrostatic waves are scattered providing propagation to the Earth surface.

We study the spatiotemporal variations of ionospheric parameters over the regions of Eurasia by analyzing data from chains of high- and mid-latitude ionosondes during the extreme magnetic storm in May 2024. The analysis of ionospheric parameters allowed us to note strong latitudinal and longitudinal differences in variations of the analyzed parameters under quiet conditions before the onset of the magnetic storm and during its development. Almost immediately after the onset of the storm at 17:00 UT on May 10, 2024, according to data from all ionosondes, a sharp drop in the electron density at the height of the F2-layer maximum was recorded, regardless of the local time at the measurement point. Ionosondes of the high-latitude chain showed a complete absence of data (radio signal blackout) during the main and early recovery phases of the storm until the evening of May 12, 2024, i.e. more than one and a half days. Additional bursts of geomagnetic activity during the recovery phase of the storm were also accompanied by significant and prolonged decreases in the electron density according to ionosonde measurements at all longitudes of Eurasia. The recovery of ionospheric ionization began on May 14–15 at all longitudes of the mid- and high-latitude regions of Eurasia. A long-term negative disturbance of electron density covering a huge territory of mid-latitude Eurasia was caused by an extraordinary, catastrophic drop in the [O]/[N2] ratio according to satellite measurements of GUVI TIMED during the superstorm for almost three days. The response of the thermospheric composition of neutral gas to the processes developing at high latitudes of the Northern Hemisphere on May 10–15, 2024 was global, with penetration of the thermospheric disturbance at almost all longitudes up to the equatorial latitudes (~10° N) and with very low values of the [O]/[N2] ratio ~0.1÷0.4. Significant differences in the spatiotemporal variations of the thermospheric composition of neutral gas were revealed during the most extreme geomagnetic storms of the current 21st century — in May 2024 and October–November 2003 (Halloween storms). The magnetic superstorm in May 2024 was much more geoeffective than the superstorms in October–November 2003, and caused a significantly different ionospheric response at different longitudes and latitudes of the Northern Hemisphere.

Abstract. A multi-year analysis of aerosol optical depth (AOD, τ) and Ångström exponent (α) was conducted using ground-based photometer data from 15 Arctic and 11 Antarctic sites. Extending the dataset of (Tomasi et al., 2015) through December 2024, the study incorporates stellar and lunar photometric observations to fill data gaps during the polar night. Daily mean values of τ at 0.500 µm and α (0.440–0.870 µm) were used to derive monthly means and seasonal histograms. In the Arctic, persistent haze events in winter and early spring lead to peak τ values. A decreasing trend in Arctic τ suggests the impact of European emission regulations, while biomass-burning aerosols are becoming more significant. In Antarctica, τ increases from the plateau to the coast. Fine-mode aerosols dominate in summer-autumn, while coarse-mode particles are more prevalent in winter-spring. Shipborne photometer data align well with ground-based measurements, confirming the reliability of mobile observations. Trend analyses using the Mann-Kendall test and Theil-Sen regression indicate a significant negative trend in τ at Andenes (−2.43 % per year), likely driven by reduced anthropogenic emissions. Antarctic stations such as Syowa and South Pole show positive trends (+3.84 % and +3.54 % per year), though these are subject to uncertainties from data limitations and instrument changes. This work contributes to the Polar-AOD network (https://polaraod.net/, last access: 15 May 2025), enhancing the understanding of aerosol variability and long-term trends in polar regions while promoting open data access for the scientific community.

In East Antarctica, ice-free areas (oases) exhibit a wide range of environmental conditions that influence soil development. Exploring the interactions between biological and abiotic factors, along with the composition and behavior of soil organic matter, offers valuable insights into how Antarctic ecosystems react to environmental stresses. This study examined the biogeochemical characteristics and molecular composition of soil organic matter in Cryosols of the Thala Hills oasis, Enderby Land, East Antarctica. The soils studied are generally shallow, with mostly coarse textures, slightly acidic to near-neutral pH levels (from 5.40 to 6.87), and very low organic carbon content in most of the samples (TOC

A comprehensive oceanographic study was conducted by a Russian oceanographic group as part of the oceanographic program during the International Antarctic Coastal Circumnavigation Expedition 2024–2025 (ICCE) aboard the R/V Akademik Tryoshnikov in November–January 2024–2025. The preliminary results of the expedition are discussed.

The results of verification of the aerodynamic method for calculating turbulent heat fluxes between the glacier and the atmosphere using the eddy covariance method are presented. The experiment was conducted on Aldegondabreen, Svalbard, in August 2022. Comparison of the methods showed a high agreement between the fluxes estimated by the two methods (R2 = 0.7), but the aerodynamic method underestimated the flux (with a mean error of 14%). The eddy covariance method allowed us to estimate the aerodynamic roughness length parameter for Aldegondabreen z0m = 0.8 mm, and the thermal roughness length z0h = 0.08 mm. The uncertainty analysis of the aerodynamic method revealed systematic errors related to the wind flow direction. The coefficient of proportionality was 0.67–0.70 for the wind direction along the glacier slope and 0.98 for the wind direction perpendicular to the glacier slope. Mean values of heat fluxes during the ablation season for the period 1991–2020 were calculated for Aldegondabreen: the shortwave balance is 72.6–113.8 W m–2; the longwave balance is 14.5 W m–2; the turbulent fluxes of sensible and latent heat determined by the aerodynamic method are 20.5 and about 1 W m–2, respectively. Thus, even allowing for a systematic method error of 14% (~3 W m–2), the total turbulent heat exchange of 24.5 W m–2 was lower than the mean estimates for the shortwave balance.

Ice cover is one of the main parameters describing the state of various water areas. The simplicity of calculation determines the frequency of using the indicator in research both for reading the seasonal course and interannual changes in the state of the ice cover and for verifying model data or reanalysis data. In this paper, ice cover is calculated based on five data sources. The comparison is based on satellite data from the NSIDC DAAC archives (October 26, 1978, to March 31, 2023; spatial resolution is 25 × 25 km, temporal resolution is 1 day; the data were collected by SMMR, SSM/I, and SSMI/S sensors on the DMSP program satellites, as well as the Nimbus-7 satellite and OSISAF (product code OSI-401-d; March 1, 2005, to present; spatial resolution is 10 × 10 km and temporal resolution is 1 day; the data were collected by the SSMI/S sensor on the DMSP program satellites). Model data from the international CMIP (Coupled Model Intercomparison Project) project are used for comparison and verification. Of the more than 40 models of the sixth phase of the project, two were selected that provided the necessary data and were suitable in terms of spatial and temporal resolution: MPI-ESM1-2-HR and AWI-CM-1-1-MR of the Max Planck Institute and the Alfred Wegener Institute, respectively. For all obtained coverage series, the mean, standard deviation, range, correlation intervals, trend coefficients, and standard error were estimated relative to the NSIDC series for the data intersection period of September 19, 2016 to June 31, 2023, in each of the Russian Arctic seas, as well as for the water area as a whole. Using the statistical characteristics, satellite data on ice cover were compared with the results of modeling in accordance with different socioeconomic trajectories (Shared Socioeconomic Pathways (SSPs)) for both models, the quality of ice cover modeling was assessed, and scenarios were selected that most closely matched the satellite data for both the entire Russian Arctic water area and for individual seas. Based on the optimal scenarios, possible changes in ice content were predicted.

<strong class="journal-contentHeaderColor">Abstract.</strong> A multi-year analysis of aerosol optical depth (AOD, &tau;) and Ångström exponent (&alpha;) was conducted using ground-based photometer data from 15 Arctic and 11 Antarctic sites. Extending the dataset of Tomasi et al. 2015 through December 2024, the study incorporates stellar and lunar photometric observations to fill data gaps during the polar night. Daily mean values of &tau; at 0.500 <em>&mu;</em>m and &alpha; (0.440&ndash;0.870 <em>&mu;</em>m) were used to derive monthly means and seasonal histograms. In the Arctic, persistent haze events in winter and early spring lead to peak &tau; values. A decreasing trend in Arctic &tau; suggests the impact of European emission regulations, while biomass-burning aerosols are becoming more significant. In Antarctica, &tau; increases from the plateau to the coast. Fine-mode aerosols dominate in summer-autumn, while coarse-mode particles are more prevalent in winter-spring. Shipborne photometer data align well with ground-based measurements, confirming the reliability of mobile observations. Trend analyses using the Mann-Kendall test and Theil-Sen regression indicate a significant negative trend in &tau; at Andenes (-2.43 % per year), likely driven by reduced anthropogenic emissions. Antarctic stations such as Syowa and South Pole show positive trends (+3.84 % and +3.54 % per year), though these are subject to uncertainties from data limitations and instrument changes. This work contributes to the Polar-AOD network (<a href="https://polaraod.net/" target="_blank" rel="noopener">https://polaraod.net/</a>; last access 15/05/2025), enhancing the understanding of aerosol variability and long-term trends in polar regions while promoting open data access for the scientific community.

Sea ice dirtiness is an important characteristic that is a marker of many processes occurring in sea ice cover throughout the period of ice formation. Data on dirty ice in the Arctic are scarce; the observations are spatially limited as they usually obtained during ship-based expeditions. There are also automated methods for dirty ice detection from satellite data. The paper presents, for the first time, maps of ice dirtiness in the East Siberian Sea based on four-class classification, drawn manually using satellite images in the visible range for the entire available period of Moderate Resolution Imaging Spectroradiometer (MODIS) data from 2000 to 2025. The spatial and temporal variability of dirty ice, as well as the conditions and causes of its formation, are studied. The study reveals that there are sea areas where the ice is always heavily dirty. At the same time, the area and location of dirty ice in the sea varies greatly from year to year. Our analysis of the interannual variability of dirty ice in the East Siberian Sea reveals an increase in dirty ice area, which is associated with the intensification of dynamic processes leading to ice contamination during its formation. The study finds that vast areas of dirty ice are formed immediately after strong wind-wave activity, which induces resuspension of sediments in the shallow water. The influx of ice from the Chukchi Sea also makes a significant contribution to the amount of dirty ice in the East Siberian Sea.