Morphological and physico-chemical properties of Cryosoils in the Bulgarian antarctic base on Livingston island, Antarctica

Under the global climatic changes and anthropogenic impacts on the environment, information about characteristics and specific features of soils in remote regions as Antarctica is valuable and could be used as references. This study focuses on the analyses of original data about the physico-chemical composition and micromorphological structure of Cryosols, collected in 2019 from the sampling area of the Bulgarian Antarctic Base “St. Kl. Ohridski” located on Livingston Island, Antarctica. The studied Cryosols are moderately acidic with slow and incomplete transformation of organic residues. The organic carbon content is low, except for soils formed under the influence of an ornithogenic factor. The mezo- and micromorphological observations show a predominance of the mineral phase, weakly affected by weathering processes. Many soil pores and voids are observed, which facilitates water-air and intra-soil exchange during the short Antarctic summer. The analyses showed an evidence for the connection of the processes of soil formation of Cryosols in the region with the pulsating degradation of the glaciers.

A new neutron monitor at the Juan Carlos I Spanish Antarctic Station (Livingston Island-Antarctic Peninsula)

Last January 2019, a new neutron monitor was installed at Juan Carlos I Spanish Antarctic Station (62º 39’ 46’’ S, 60º23’20’’ W, 12 m asl) located in Livingston Island (South Shetland Archipelago) close to the Antarctic Peninsula. The vertical rigidity cut-off for this new station is estimated as 3.52 GV. This new station (ORC) is composed of a BF3-based 3NM64 (ORCA) and 3 bare BF3 counters (ORCB). The neutron monitor is complemented by a muon telescope sharing a common room in a single stack. ORCA and ORCB with the Castilla-La Mancha neutron monitor (CaLMa) are the Spanish contributions to the Neutron Monitor Data Base. Because Juan Carlos I station is a summer station, one minute data is providing once a day during the Antarctic summer. One hour data are sent once a day during Antarctic winter. First measurements and future plans are provided in this work.

Evaluation of the MODIS (C6) Daily Albedo Products for Livingston Island, Antarctic

Although extensive research of Moderate Resolution Imaging Spectroradiometer (MODIS) albedo data is available on the Greenland Ice Sheet, there is a lack of studies evaluating MODIS albedo products over Antarctica. In this paper, MOD10A1, MYD10A1, and MCD43 (C6) daily albedo products were compared with the in situ albedo data on Livingston Island, South Shetland Islands (SSI), Antarctica, from 2006 to 2015, for both all-sky and clear-sky conditions, and for the entire study period and only the southern summer months. This is the first evaluation in which MYD10A1 and MCD43 are also included, which can be used to improve the accuracy of the snow BRDF/albedo modeling. The best correlation was obtained with MOD10A1 in clear-sky conditions (r = 0.7 and RMSE = 0.042). With MCD43, only data from the backup algorithm could be used, so the correlations obtained were lower (r = 0.6). However, it was found that there was no significant difference between the values obtained for all-sky and for clear-sky data. In addition, the MODIS products were found to describe the in situ data trend, with increasing albedo values in the range between 0.04 decade−1 and 0.16 decade−1. We conclude that MODIS daily albedo products can be applied to study the albedo in the study area.

Epiphytic diatom community structure and richness is determined by macroalgal host and location in the South Shetland Islands (Antarctica)

The marine waters around the South Shetland Islands are paramount in the primary production of this Antarctic ecosystem. With the increasing effects of climate change and the annual retreat of the ice shelf, the importance of macroalgae and their diatom epiphytes in primary production also increases. The relationships and interactions between these organisms have scarcely been studied in Antarctica, and even less in the volcanic ecosystem of Deception Island, which can be seen as a natural proxy of climate change in Antarctica because of its vulcanism, and the open marine system of Livingston Island. In this study we investigated the composition of the diatom communities in the context of their macroalgal hosts and different environmental factors. We used a non-acidic method for diatom digestion, followed by slidescanning and diatom identification by manual annotation through a web-browser-based image annotation platform. Epiphytic diatom species richness was higher on Deception Island as a whole, whereas individual macroalgal specimens harboured richer diatom assemblages on Livingston Island. We hypothesize this a possible result of a higher diversity of ecological niches in the unique volcanic environment of Deception Island. Overall, our study revealed higher species richness and diversity than previous studies of macroalgae-inhabiting diatoms in Antarctica, which could however be the result of the different preparation methodologies used in the different studies, rather than an indication of a higher species richness on Deception Island and Livingston Island than other Antarctic localities.

Approach to study the seismicity in the Perunica Glacier, Livingston Island, Antarctica

<p>The seismicity caused by the movement of glaciers was discovered only 30-40 years ago, and it was initially assumed that only glaciers in Greenland create this type of seismicity. Today, a significant part of the earthquakes registered by the Antarctic seismic stations are of glacial origin. In recent years, scientists' interest in studying the seismic activity of glaciers and its relationship to various environmental factors has increased due to the response of the ice mass to climate change.</p><p>The interest of studying seismicity of Antarctica has increased in the last decade with installation of a growing number of seismic stations in the region.</p><p>In 2015, with the first installation of the LIVV seismic station, Bulgarian seismologists began studying the seismicity of the Perunika Glacier, located on Livingston Island, Antarctica. Between 2015 and 2018, seismic recordings were made only in the astral summer, and from January 2020 the seismic station was installed for year-round operation. The seismic station is located near the glacier.</p><p>In this study, an approach to analyze the ice generated events recorded during all working period of the LIVV station is presented. Depending on the source mechanism and therefore the different waveform shapes, several types of icequakes and earthquakes are distinguished.</p><p><span>Registered icequakes are more than 16000. Its duration varies between less than a second and more than a minute. A few events are several minutes long. We</span> <span>have noticed that from 2015 to 2020, the number of glacier events is increasing while its duration is decreasing. </span></p><p>Localization of the ice generated events with duration below 1 s is calculated. In the localization procedure, a velocity model developed for the area of the seismic station is applied. The produced icequake epicenters are grouped in several clusters within the Perunika glacier. The nature of these glacier events are still studying.</p><p><span>Another approach to study the seismic activity of the glacier is carried out by estimating the ambient seismic noise. Frequent and spectral distribution of the power of seismic noise is made over the seismic data recorded during all working periods. It is concluded that </span><span>t</span>he noise sources in the periods around 0.5 s are linked to the dynamic processes in the Perunika Glacier<span>.</span> Some relationship between the change in <span>the </span>noise power in the 0.2-0.6s period band and tidal cycles has been found.</p><p><span><strong>Acknowledgment:</strong></span><span> The presented study is supported by project: No 70.25-171/22.11.2019 “Study the activity of the Perunika glacier during year-round deployment” funded by the </span><span>National Center for Polar Studies, Bulgaria</span><span>.</span></p>

Post-Last Glacial Maximum ice thinning and glacier dynamics in the Hurd Peninsula ice cap (Livingston Island, South Shetland Islands, Antarctic Peninsula)

<p>In the Antarctic Peninsula (AP), the small ice caps distributed across its periphery and surrounding islands have recorded important ice volume changes since the end of the Last Glacial Cycle. These volume changes have occurred in the form of surface extent shrinking and ice thinning. The latter has been investigated only at a reduced number of locations. In this context, nunataks constitute key spots to assess the environmental evolution of deglaciated areas as they offer the opportunity to track the deglaciation history and reconstruct past ice losses by using Cosmic-Ray Exposure (CRE) dating. Indeed, nunataks are supposed to have played a prominent role in the vegetal and animal colonization of Antarctica.</p><p>The South Shetland Islands archipelago is one of the AP areas where past ice thinning has been least investigated, with only one study conducted in King George Island. In order to shed some light on the last deglaciation and its associated ice thinning, we apply <sup>10</sup>Be CRE dating to vertical sequences of glacially polished outcrops on two palaeonunataks and one nunatak distributed across the ice-cap covering part of the Hurd Peninsula (SW of Livingston Island): Reina Sofía Peak (62°40'8" S, 60°22'51" W, 273 m a.s.l.), Moores Peak (62°41'21" S, 60°20'42" W, 407 m a.s.l.) and Napier Peak (62°40'18"S, 60°19'31" W, 382 m a.s.l.).</p><p>Most of the resulting exposure ages provided a logical chronological sequence and allowed reconstructing past vertical changes of the ice surface. The uppermost surfaces of the Moores and Reina Sofía peaks became deglaciated during the Last Glacial Maximum (LGM), between ~24 ka and ~20 ka. Following the LGM, between ~20 and ~14 ka (Termination-1), a massive deglaciation occurred. This trend was especially exacerbated at around ~14 ka, triggering the onset of the deglaciation at other nunataks, such as the Napier Peak, in good agreement with the coetaneous global melt-water pulse 1a. From our results, we infer that ice shrinking during the Holocene must have been very limited compared to the post-LGM period.</p><p>Nevertheless, some of the exposure ages were either anomalously old or inconsistent, such as those found at the summits of the Reina Sofía and Moores peaks or at the base of the Napier nunatak. These artifacts suggest the occurrence of nuclide inheritance and are indicative of the conservation of previously exposed surfaces. These ages allow to qualitatively infer cold-based regimes characterized by basal ice frozen to bed, with slow mobility and inefficient subglacial erosion due to the gentle slope gradient, not capable of removing inherited nuclides accumulated during former exposure periods. But, as a whole, the dataset adds valuable knowledge on the polythermal character of the Hurd Peninsula Ice cap.</p><p> </p><p>This paper was supported by the project NUNANTAR (02/SAICT/2017 – 32002; Fundação para a Ciência e a Tecnologia, Portugal) and the College on Polar and Extreme Environments (University of Lisbon).</p>

Tephra layers in Perunika Glacier, Livingston Island, Antarctica

<p>Perunika Glacier is an 8 km long and 3 km wide roughly crescent-shaped glacier in Livingston Island, South Shetland Islands, Antarctica. The glacier is heavily crevassed in its lower half receiving ice influx from snowfields and from part of the islands ice cap.</p><p>Tephra layers recorded in the ice caps are very common in Antarctica, and Perunika Glacier is not an exception. The glacier contains several dark layers of unconsolidated ash (tephra), resulting the most probably from volcanic activities at Deception Island, a large active volcano in Bransfield Strait situated 40 km south of the tephra outcrops on Livingston Island (Pallas et al., 2001). Three eruptions have been documented in recent history – 1967, 1969 and 1970. The most powerful and intensive of which was in 1970.</p><p>The ice and tephra stratigraphy seen in the ice cliffs is the result of deposition within the accumulation zone in the interior of the island. The distortion of tephra layers during glacial transport and ablation may result in different local tephra stratigraphies. The distinctive grouping and spacing of the multiple tephra layers is repeated at many localities.</p><p>In the cliff of Perunika Glacier there are 10 tephra layers. During the 26th Bulgarian Antarctic Expedition 7 of them were observed, the other were inaccessible. The lower six levels are located at relatively equal intervals and have thicknesses between 3 cm and 5 cm. The layer 7 is situated about 10 m above the others and is 10–12 cm thick. All tephra layers consist predominantly of black and subordinately of red components. In this research is shown data about phase composition of the tephra layers, based on X-ray diffraction analysis.</p><p>The obtained phase composition by Powder X-ray diffraction corresponds with basalt and basaltic andesite from the published data on chemical content of the tephroid levels by Pallas et al. (2001). As main phases of samples at 7 assayed levels were determained plagioclase (34–47%) and pyroxene (7–10%). Diffraction lines analysis defines two types of plagioclase – anorthite and sodic anorthite. Comparison between registered diffraction lines and different pyroxene types from the reference database identifies pyroxene from all samples as ferrian diopside. In three of the levels was discovered andalusite (2–6%) and mica (5–7%). Due to low mica content in the samples, it is difficult to define its type by powder analysis. However, in samples from levels 1, 2, 3, 5, and 7 the mica is probably sericite type and in levels 4 and 6 – biotite type. The presence of xenocrystals of andalusite and micas (biotite and sericite) is interesting. Considering their metamorphic genesis, the most reasonable source is the metamorphic fundament of this Antarctic area. The lithotypes it is built are represented by phyllites, schists, Ca-silicate rock types, marbles, rare amphibolites and fine layers of volcanic metaconglomerates (Marsh, Thompson, 1985).</p>

Transition from a Subaerial to a Subnival Permafrost Temperature Regime Following Increased Snow Cover (Livingston Island, Maritime Antarctic)

The Antarctic Peninsula (AP) region has been one of the regions on Earth with strongest warming since 1950. However, the northwest of the AP showed a cooling from 2000 to 2015, which had local consequences with an increase in snow accumulation and a deceleration in the loss of mass from glaciers. In this paper, we studied the effects of increased snow accumulation in the permafrost thermal regime in two boreholes (PG1 and PG2) in Livingston Island, South Shetlands Archipelago, from 2009 to 2015. The two boreholes located c. 300 m apart but at similar elevation showed different snow accumulation, with PG2 becoming completely covered with snow all year long, while the other remained mostly snow free during the summer. The analysis of the thermal regimes and of the estimated soil surface energy exchange during the study period showed the effects of snow insulation in reducing the active layer thickness. These effects were especially relevant in PG2, which transitioned from a subaerial to a subnival regime. There, permafrost aggraded from below, with the active layer completely disappearing and the efficiency of thermal insulation by the snowpack prevailing in the thermal regime. This situation may be used as an analogue for the transition from a periglacial to a subglacial environment in longer periods of cooling in the paleoenvironmental record.