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ABSTRACT Antarctic krill (Euphausia superba; krill) and the pelagic tunicate (Salpa thompsoni; salps) are crucial to the Southern Ocean ecosystem, and krill supports the largest fishery in the Southern Ocean in term of catch. Given recent climatic changes in the northern Antarctic Peninsula (NAP), the distribution of krill and salps are shifting poleward. Unlike krill, salps thrive in warmer water temperatures and can form large blooms under favorable conditions, potentially outcompeting krill for resources. However, krill are ecologically more important, serving as a primary food source for higher trophic levels. The interspecific interactions, including hotspots and ecological niches, of krill and salps in the NAP were therefore investigated using historical datasets and species distribution models. We found that both spatial separation and overlap occurred between krill and salps hotspots, with the primary overlap occurring around Elephant Island. Furthermore, there was a significant overlap in their ecological niches, suggesting that they may have similar ecological requirements. This study emphasized the importance of krill and salps interactions in the Southern Ocean ecosystem. The krill habitat and therefore food web of the Southern Ocean could be influenced significantly if salps continue to shift poleward in the future. The information provided in this study aids in the conservation and management of the Southern Ocean ecosystem. [ABSTRACT FROM AUTHOR]

Historical data on chinstrap penguin (Pygoscelis antarctica) breeding population sizes are sparse and sometimes highly uncertain, making it hard to estimate true population trajectories. Yet, information on population trends is desirable as changes in population size can help inform conservation assessments. Recently, Krüger (2023) (Diversity 2023, 15, 327) used chinstrap penguin nest count data to predict breeding colony size trends between 1960 and 2020, to estimate whether the level of population change within three generations exceeded IUCN Red List Criteria for "Vulnerable" populations. Chinstrap penguin population trends are an important research topic, but we caution that Krüger (2023)'s statistical analyses (intended to form the foundation for drawing valid, evidence-based inferences from sparse data) contain fundamental errors that invalidate that paper's findings. We discuss oversights in several key steps (data processing, exploratory data analysis, model fitting, model evaluation, and prediction) of that paper's analysis to help others detect and avoid some of the pitfalls associated with estimating population trends via mixed models. We also show through reanalysis that improved statistical modelling can yield better predictions of chinstrap penguin population trends, at least within the range of observed data. This case study highlights (1) the profound influence that seemingly minor differences in modelling procedures (both unintentional errors and other decisions) can have on predictions of population trends, and (2) the substantial inherent uncertainty in population trend predictions derived from sparse, heterogenous data. [ABSTRACT FROM AUTHOR]

The diet of the Antarctic shags was investigated at Paradise Bay, Antarctic Peninsula, by the analysis of 20 pellets collected during the 2015/16 breeding season. Fish were the most frequent and important prey, accompanied by Polychaetes. Amongst fish, only benthic-demersal species were represented in the diet. Harpagifer antarcticus, followed by Notothenia coriiceps, was the most frequent prey and the most important by number and mass. The results are compared with the diet reported for this shag at other localities of the South Shetland Islands and of the Antarctic Peninsula and discussed in terms of geographical significance, breeding output, and population trend. [ABSTRACT FROM AUTHOR]

The Scotia Sea is the most densely distributed area of Antarctic krill (Euphausia superba) resources, and is also the traditional fishing ground for krill fishery, but population structure of krill is complex and varies widely in this region. It plays the key role of females in the population for stabling structure and maintaining size of population. In order to understand the population dynamics of krill in this region, the temporal and spatial variability in female stock of krill resource in this region was analyzed using samples randomly collected by fishery surveys from January to September, 2016 to 2022. The results showed that there were significant differences in the development stages of krill annually. During 2016-2022, female krill stock was mainly dominated by subadults, followed by adults, and the proportion of juveniles was low. For the perspective of the annual variation of sexual maturity, the proportions of subadults (stages 2FC and 2FD) were generally higher than that of stage 2FB individuals. In terms of seasons, the female stock structure was relatively simple in winter and spring, while that was very complex in summer and autumn, the subadults was predominant in the stock. In addition, the structure of female krill stock was different between regions, the proportion of adults in the South Orkney Islands was the highest (65. 4%), while the subadults was predominant in the stock (89. 9%) and no juveniles occurred at South Georgia. [ABSTRACT FROM AUTHOR]

The Pelagornithidae are an extinct group of soaring birds that lived all over the world between the early Palaeocene and the Pliocene-Pleistocene and are characterised by the presence of hollow denticles along the tomial edges formed by the expansion of the premaxillary, maxillary, and dentary bones. The presence of distinctive sulci in the upper and lower jaws together with the absence of wearing signs on the denticles, attributable to the handling of the prey, indicates the development of a resistant and compound rhamphotheca. To reconstruct it, we turned to the evidence provided by extant representatives with similar configurations and the osteological correlates of the beak. As a result, we propose a model for the middle-latest Eocene Antarctic Pelagornithidae, in which the rhamphotheca would have been formed by thick horny plates. The culminicorn was separated from the laternicorn by an extense sulcus nasi that continuous caudally to the apertura nasi ossea, a sturdy and hooked unguis maxillaris covering the rostrum, with small nares opening at the cranial end of the apertura nasi ossea, dorsal and ventral ramicorns, and a thick unguis mandibularis with a pseudomental fold and a sulcus on the mandible. [ABSTRACT FROM AUTHOR]

Predator-prey interactions in marine ecosystems control population sizes, maintain species richness, and provide intermediate disturbance. Such ecosystem structuring interactions may be rare in Antarctic epibenthic communities, which are unique among marine ecosystems worldwide for their dominance of soft bodied fauna (sponges, soft and hard corals, and echinoderms) and a simultaneous paucity of shell crushing predators (sharks, rays and durophagous decapods). In the shallow benthos, instead of durophagy, important Antarctic predators such as starfish, pycnogonids (sea spiders), nemertean worms, and nudibranchs employ grazing, scavenging, or sucking strategies. Far less is known about deep sea (>1000 m) Antarctic benthic communities due to the challenging nature of polar data collection, so that photographic surveys provide one of the only means of making in situ observations of these deep sea communities. We used seabed photographs of the deep (~2000m) slope of the Powell Basin, northwest Weddell Sea, taken by the Ocean Floor Observation and Bathymetry System on board the RV Polarstern (PS118, April 2019) to investigate the epibenthic community composition, and Bayesian Network Inference (BNI) to determine the ecological network, namely the ecological associations, including potential invertebrate predator-prey relationships between taxa. Photographs show that the rocky substrates of the basin slope support between 10-22 morphotaxa per photo, and highly abundant communities (density between 106 to 553 individuals/m2). BNI results reveal a network of associations between the sessile and mobile suspension and filter feeding organisms and their physical environment. However, associations between invertebrate predators like starfish, and other organisms, were not detected in the network. This lack of inclusion within the network suggests that, despite the presence of these normally important mobile predators, invertebrate predator-prey interactions on the rocky Powell Basin slope do not have the same ecosystem-regulating impact that they do on shallow Antarctic epibenthic communities. [ABSTRACT FROM AUTHOR]

We developed an enhanced Kalman‐based approach to quantify abrupt changes and significant non‐linearity in vertical land motion (VLM) along the coast of Chile and the Antarctic Peninsula using a combination of multi‐mission satellite altimetry (ALT), tide gauge (TG), and GPS data starting from the early 1990s. The data reveal the spatial variability of co‐seismic and post‐seismic subsidence at TGs along the Chilean subduction zone in response to the Mw8.8 Maule 2010, Mw8.1 Iquique 2014, and Mw8.3 Illapel 2015 earthquakes that are not retrievable from the interpolation of sparse GPS observations across space and time. In the Antarctic Peninsula, where continuous GPS data do not commence until ∼1998, the approach provides new insight into the ∼2002 change in VLM at the TGs of +5.3 ± 2.2 mm/yr (Palmer) and +3.5 ± 2.8 mm/yr (Vernadsky) due to the onset of ice‐mass loss following the Larsen‐B Ice Shelf breakup. We used these data to constrain viscoelastic Earth model parameters for the northern Antarctic Peninsula, obtaining a preferred lithosphere thickness of 115 km and upper mantle viscosity of 0.9 × 1018 Pa s. Our estimates of regionally‐correlated ALT systematic errors are small, typically between ∼±0.5–2.5 mm/yr over single‐mission time scales. These are consistent with competing orbit differences and the relative errors apparent in ALT crossovers. This study demonstrates that, with careful tuning, the ALT‐TG technique can provide improved temporal and spatial sampling of VLM, yielding new constraints on geodynamic models and assisting sea‐level change studies in otherwise data sparse regions and periods. Plain Language Summary: The difference in sea‐level records from satellite altimeters and coastal tide gauges can reveal the Earth surface's vertical land motion (VLM) and potential errors in either system. Time‐varying changes in the VLM can occur because of phenomena such as earthquakes or glacier melt which changes the mass load on the crust. We developed a flexible data combination framework to use records from multi‐mission altimeters (ALTs), tide gauges (TGs), and GPS sites to allow the estimation of substantial non‐linear VLM that complements the previous estimates which can be sparse in the 1990s especially. We considered the study period since the launch time of TOPEX mission in ∼1992. We used our new approach to investigate the earthquake‐induced deformation at TG locations along the near‐coast subduction zone in Chile that could not be inferred from temporally and spatially sparse GPS records. We also provide insights into the rapid change in VLM at coastal TGs in the Antarctic Peninsula after the Larsen‐B Ice Shelf breakup in ∼2002, where the existing knowledge dates to ∼1998 from only one GPS at Palmer station. These significant insights into present‐day deformation help to fill the knowledge gap from GPS‐inferred records and improve VLM sampling across space and time. More generally, this new approach may assist resolve complex VLM for sea‐level studies globally and could add new constraints to inverse geophysical modeling, especially where GPS data are sparse in space and/or time. Key Points: We developed an advanced Kalman approach to estimate highly non‐linear vertical land motion using altimeter, tide gauge and GPS data, while simultaneously capturing significant mission‐specific systematic errorsWe derived new estimates of pre‐seismic velocity, co‐seismic jumps, and post‐seismic velocity at tide gauges in Chile that add additional constraints on the solid‐Earth response to major earthquakes in the regionWe observed the onset of rapid uplift at tide gauges in the Antarctic Peninsula caused by the 2002 breakup of the Larsen‐B Ice Shelf, filling a historical knowledge gap from GPS records and further constraining modeled viscoelastic deformation [ABSTRACT FROM AUTHOR]

The Antarctic Digital Magnetic Anomaly Project is an international research effort to construct a magnetic map of the continent based on ground, satellite, marine, and aeromagnetic surveys. This paper reports the magnetic mapping of the shelf zone in the SE part of the Wilhelm Archipelago, West Antarctica, based on magnetic surveys conducted with Zodiac boats. A spectacular feature of this area is the strong magnetic anomaly of the Antarctic Peninsula (AP) batholith, which was the product of subduction-related Mesozoic–Cenozoic arc magmatism on the former margin of Western Gondwana. We constructed and analyzed a detailed magnetic map of magnetic field anomalies using field observations of rock exposures on the islands and magnetic properties of rocks from laboratory data. The oldest volcanic rocks of Jurassic to Lower Cretaceous age relate to N-NE trending bands of negative magnetic field. The largest feature in the study area is an Upper Cretaceous/Paleogene granodiorite complex that produces a positive magnetic anomaly. Many smaller anomalies are also present over gabbroid bodies of Cretaceous age. Two-dimensional magnetic modeling shows that heterogeneities in the upper crust may have magnetic susceptibilities in the range of 0.005–0.13 SI. Magnetic field anomalies also delineate an orthogonal system of tectonic faults, including the main NE fault along the Penola Strait (sub-parallel to the AP coastline) and four intersecting faults. These fault systems may be associated with different stages of continental margin evolution along the Antarctic Peninsula. [ABSTRACT FROM AUTHOR]

Several studies have examined the potential impacts of climate change on the abundance and distribution of Antarctic penguin species, particularly in the genus Pygoscelis. However, less attention has been given to traditionally sub-Antarctic penguin species. The Macaroni Penguin (Eudyptes chrysolophus) is one such sub-Antarctic species whose presence in Antarctica has historically been restricted to colonies on the South Shetland Islands and adjacent islands, but their status in the region has not been updated in decades. We compiled census data on all known Macaroni Penguin breeding colonies in the Antarctic Peninsula region in order to estimate the total Antarctic population. We estimate a population of 8053 breeding pairs for the region, which represents an approximately 10.7% increase since the last regional census in 1993. We identify local population changes at different colonies in comparison to historical census data. We also identify vagrant sightings in the region, as they may reflect prospecting of new breeding habitat, especially as ice-free areas continue to expand due to climate change. Our assessment identifies the South Shetland Islands and South Orkney Islands as notable data gaps. [ABSTRACT FROM AUTHOR]

Geochemical compositions can be used to determine the tectonic setting of sedimentary basins, while where the link of source to sink is no longer preserved, detrital zircon age patterns can aid in resolving the original basin setting. The metasedimentary Legoupil Formation, located at Cape Legoupil and the Schmidt Peninsula, could give a hint for the tectonic evolution of Antarctic Peninsula. In this contribution, we constrain the sedimentary provenance of the Legoupil Formation through geochemistry and detrital zircon U-Pb geochronology. The petrography and geochemical features indicate that the provenance of the Legoupil Formation could be felsic rocks. Detrital zircon grains record a steady supply of Permian and Ordovician material into the Legoupil Formation. The youngest concordant zircon ages of 262 Ma suggest that the depositional time of Legoupil Formation is no older than Late Permian. The detrital zircon age spectrum of Legoupil Formation suggests that the Legoupil Formation sediments should be derived from regional sources endemic to western Gondwana prior to its breakup. Together with the previous studies, geochemistry and detrital zircons reflect an active continental margin tectonic setting and the detrital zircon spectra of Legoupil Formation are similar to the ones deposited in forearc tectonic setting. [ABSTRACT FROM AUTHOR]

Several new gabbroid intrusions were discovered in the process of geological surveying in the area of the Ukrainian research station in the West Antarctica. One of them is located in the hard-to-reach Girard Bay on the western coast of the Kyiv Peninsula. The authors investigated the mode of occurrence, petrography and mineral chemistry of Girard Bay gabbroids in order to clarify their geological position and petrogenetic conditions of their formation. It was found that the newly discovered gabbroids make up a stock-like intrusive body with a horizontal dimension of more than 3 km. Gabbroids unconformably intrude the Kyiv Peninsula volcanic formation. The apical part of this gabbroid intrusion is exposed fragmentarily on the southern coast of Girard Bay. The petrographic diversity of the studied gabbroids depends on the heterogeneous manifestation of local low-temperature hydrothermal transformations (amphibolization, prenitization and silicification). In addition, the presence of hidden magmatic layering, which is characteristic of other gabbroid intrusions of the region, is assumed. The main petrographic representatives are gabbronorites and amphibolized gabbros, among which mesocratic and leucocratic varieties have been identified. The gabbronorites exposed on the southern coast of Girard Bay represent one of the lowest degrees of the post-magmatic transformation. Mineralogical and petrographic features point to hypabyssal depths of their formation. The chemistry of pyroxenes and plagioclases indicates the most high-temperature conditions of crystallization in comparison with other representatives of gabbroids both on the Kyiv Peninsula and on the neighbouring Wilhelm Archipelago. The geological age of Girard Bay gabbroids is preliminarily defined as post-Jurassic and requires further clarification using the isotopic geochronology methods. Given the possible post-magmatic re-equilibration of primary mineral paragenesis, zircon is recommended as a chronometer mineral. [ABSTRACT FROM AUTHOR]

Predator-prey interactions in marine ecosystems control population sizes, maintain species richness, and provide intermediate disturbance. Such ecosystem structuring interactions may be rare in Antarctic epibenthic communities, which are unique among marine ecosystems worldwide for their dominance of soft bodied fauna (sponges, soft and hard corals, and echinoderms) and a simultaneous paucity of shell crushing predators (sharks, rays and durophagous decapods). In the shallow benthos, instead of durophagy, important Antarctic predators such as starfish, pycnogonids (sea spiders), nemertean worms, and nudibranchs employ grazing, scavenging, or sucking strategies. Far less is known about deep sea (>1000 m) Antarctic benthic communities due to the challenging nature of polar data collection, so that photographic surveys provide one of the only means of making in situ observations of these deep sea communities. We used seabed photographs of the deep (~2000m) slope of the Powell Basin, northwest Weddell Sea, taken by the Ocean Floor Observation and Bathymetry System on board the RV Polarstern (PS118, April 2019) to investigate the epibenthic community composition, and Bayesian Network Inference (BNI) to determine the ecological network, namely the ecological associations, including potential invertebrate predator-prey relationships between taxa. Photographs show that the rocky substrates of the basin slope support between 10-22 morphotaxa per photo, and highly abundant communities (density between 106 to 553 individuals/m2). BNI results reveal a network of associations between the sessile and mobile suspension and filter feeding organisms and their physical environment. However, associations between invertebrate predators like starfish, and other organisms, were not detected in the network. This lack of inclusion within the network suggests that, despite the presence of these normally important mobile predators, invertebrate predator-prey interactions on the rocky Powell Basin slope do not have the same ecosystem-regulating impact that they do on shallow Antarctic epibenthic communities.

Historical data on chinstrap penguin (Pygoscelis antarctica) breeding population sizes are sparse and sometimes highly uncertain, making it hard to estimate true population trajectories. Yet, information on population trends is desirable as changes in population size can help inform conservation assessments. Recently, Krüger (2023) (Diversity 2023, 15, 327) used chinstrap penguin nest count data to predict breeding colony size trends between 1960 and 2020, to estimate whether the level of population change within three generations exceeded IUCN Red List Criteria for “Vulnerable” populations. Chinstrap penguin population trends are an important research topic, but we caution that Krüger (2023)’s statistical analyses (intended to form the foundation for drawing valid, evidence-based inferences from sparse data) contain fundamental errors that invalidate that paper’s findings. We discuss oversights in several key steps (data processing, exploratory data analysis, model fitting, model evaluation, and prediction) of that paper’s analysis to help others detect and avoid some of the pitfalls associated with estimating population trends via mixed models. We also show through reanalysis that improved statistical modelling can yield better predictions of chinstrap penguin population trends, at least within the range of observed data. This case study highlights (1) the profound influence that seemingly minor differences in modelling procedures (both unintentional errors and other decisions) can have on predictions of population trends, and (2) the substantial inherent uncertainty in population trend predictions derived from sparse, heterogenous data.

The response to climate change in highly dimorphic species can be hindered by differences between sexes in habitat preferences and movement patterns. The Antarctic fur seal, Arctocephalus gazella, is the most abundant pinniped in the Southern Hemisphere, and one of the main consumers of Antarctic krill, Euphausia superba, in the Southern Ocean. However, the populations breeding in the Atlantic Southern Ocean are decreasing, partly due to global warming. Male and female Antarctic fur seals differ greatly in body size and foraging ecology, and little is known about their sex‐specific responses to climate change. We used satellite tracking data and Earth System Models to predict changes in habitat suitability for male and female Antarctic fur seals from the Western Antarctic Peninsula under different climate change scenarios. Under the most extreme scenario (SSP5‐8.5; global average temperature +4.4°C projected by 2100), suitable habitat patches will shift southward during the non‐breeding season, leading to a minor overall habitat loss. The impact will be more pronounced for females than for males. The reduction of winter foraging grounds might decrease the survival of post‐weaned females, reducing recruitment and jeopardizing population viability. During the breeding season, when males fast on land, suitable foraging grounds for females off the South Shetland Islands will remain largely unmodified, and new ones will emerge in the Bellingshausen Sea. As Antarctic fur seals are income breeders, the foraging grounds of females should be reasonably close to the breeding colony. As a result, the new suitable foraging grounds will be useful for females only if nearby beaches currently covered by sea ice emerge by the end of the century. Furthermore, the colonization of these new, ice‐free breeding locations might be limited by strong female philopatry. These results should be considered when managing the fisheries of Antarctic krill in the Southern Ocean. [ABSTRACT FROM AUTHOR]

The waters near the Antarctic Peninsula have always been a hot spot because of their variable and unique oceanographic conditions. To distinguish the differences in phytoplankton communities, we conducted a mesoscale survey during the austral summer of 2018. Samples were collected at 14 stations located in the Drake Passage, South Shetland Islands (SSI) and South Orkney Islands (SOI). A total of 615 operational taxonomic units were extrapolated using V4-5 18S rDNA sequencing collected from the chl amax layers. Three groups (I, II, and III) were divided at a similarity level of 60% by multivariate statistical analysis, and there were significant differences between groups II and III. Generally, diatoms and dinoflagellates predominated among all three groups. Chlorophyta was found in greater abundance near the SSI, whereas pennate diatoms contributed more around the SOI. The different abundance of particular dinoflagellates was the reason for grouping by SIMPER analysis. And Pseudochattonella farcimen, Micromonas sp. and Pyramimonas sp were screened out which inducing dissimilarity were less mentioned in other literatures. Temperature and salinity among stations showed little difference in our study. Phytoplankton assemblage was a complex issue and the factors induced the difference of phytoplankton communities need to further analyze. [ABSTRACT FROM AUTHOR]

The northern part of James Ross Island is the largest deglaciated area in the Antarctic Peninsula region with a unique ecosystem created during the Late Glacial. This research aims to evaluate the degree of contamination of the locality with toxic metals (As, Hg, Cd, and Pb) through bioindicators in the aquatic environment—colonies of cyanobacteria and algae. For this purpose, bottom lake sediments of Big Lachman Lake were studied for contents of Fe, As, Hg, Cd, Pb, Cr, Co, Ni, Cu, and Zn, as well as samples of cyanobacterial mat, in which Fe, As, Hg, Cd, and Pb were determined. Metal contents were determined by means of inductively coupled plasma optical emission spectrometry and atomic absorption spectrometry. The contents of metals in sediments did not differ from the usual values in the area of the Antarctic Peninsula. The bioaccumulation of metals in cyanobacterial mat was evaluated by calculating enrichment factors (the calculation to Fe as a reference element). According to this method, moderate pollution of Big Lachman Lake was confirmed for Hg and Cd. [ABSTRACT FROM AUTHOR]

Palynological analysis of Upper Cretaceous marine rocks from the Rabot and Snow Hill Island formations, James Ross Basin, northeastern Antarctic Peninsula, has revealed the record of a previously undescribed dinoflagellate cyst species, previously assigned to Oligosphaeridium sp. A. Here, we provide a formal description of this new species, which we name Stiphrosphaeridium sobralii sp. nov. and we add some features to the description of the genus Stiphrosphaeridium. The new species is found in Campanian strata, which are calibrated with magnetostratigraphic data. It is considered an important Late Cretaceous biostratigraphic marker commonly recorded in offshore environments of Antarctica.

Ice shelves play an essential role in the dynamics of the Antarctic ice sheet. The surface meltwater is important, as it can irreversibly weaken ice shelves by exerting additional hydrostatic pressure. Therefore, high-resolution snowmelt products are urgently needed to accurately analyze melting patterns of ice shelves and further estimate mass loss. In this study, a new high-resolution (40 m) snowmelt dataset over all of the Antarctic Peninsula ice shelves larger than 100 km$^2$ was developed based on the modified snowmelt detection framework by using a co-orbit normalization method. The dataset provides detailed snowmelt information on each ice shelf, including the image coverage, melting area and melting ratio every 5 days. The melting patterns of three typical ice shelves (George VI, Wilkins and Larsen C Ice Shelves) and the spatio-temporal melting distribution of the Antarctic Peninsula (AP) were further analyzed. The snowmelt information indicates that both the extent and duration of snowmelt have been increasing in the Antarctic Peninsula from 2015 to 2021, and we found that the snowmelt on the Antarctic Peninsula showed a spatial pattern of significantly intense snowmelt on the western side. We believe this study will provide essential data for ice shelf investigation to support other fields of polar research.

Snow algal blooms have a remarkable climatic or environmental effect through influencing the snow–albedo feedback, accelerating the melting of surface snow, and amplifying global warming. Snow algal blooms occurred frequently on King George Island, Antarctic, during the recent six austral summers (December to next February) through 2017–2022. Based on an assessment of satellite images, this study found that the range and amount of snow algal blooms in the summers of 2018, 2020, 2021 and 2022 are relatively larger than in the summers of 2017 and 2019. Whether meteorological conditions have shaped the year-to-year variation of algal bloom intensities is analyzed through observational composite. The results suggest that during the strong bloom summers there exist prevailing northerly or northwesterly wind anomalies which advect warm and humid airmass from the southern ocean into the island, increasing surface air temperature and humidity; the warmer and more humid surface favors melting of snow and an increase of low cloud cover, subsequently enhancing the atmospheric downward long-wave radiation and amplifying surface warmth; the increased low cloud cover reflects more ultraviolet rays back to space and weakens the short-wave radiation reaching the surface. All these factors together favor to a stronger bloom. In comparison, during 2017 and 2019 there exist weak southerly wind anomalies which induce the northward advection of cold and dry air from the Antarctic Continent and favor the cooler surface. Consequently, it is unfavorable for the snow algal bloom. Based on these results, a snow algal bloom potential index (API) integrating the meteorological conditions is constructed, and its future trend is projected based on the EC-Earth3 run attending the CMIP6 under SSP245 and SSP585. A significant increasing trend is projected especially under SSP585. Thus snow algal bloom on King George Island will become more frequent and stronger in future. This implies a potential accelerate melting of ice shelf over Antarctic Peninsula.

This note reports observations of two moulting emperor penguins (Aptenodytes forsteri) on Horseshoe Island, West Antarctica, during the Seventh Turkish Antarctic Expedition in February 2023. This is the first time this species has been documented on this island. Emperor penguins largely depend on fast-ice to breed and moult. The Antarctic Peninsula hosts few emperor penguin colonies. Horseshoe Island has become one of the northernmost points along the western Antarctic Peninsula where emperor penguins are documented to moult.

The preliminary results of geochemical analyses of the surface sediments from 4 lakes on Robert Island, South Shetland, Antarctica, are presented herein. The samples were collected during the Turkish Antarctic Expedition (TAE-II) in 2018. Sediment samples were obtained from the littoral zone (approximately 20 cm) of 4 different lakes exposed on the glacier-free land area on Robert Island. The lake sediments predominantly consist of fine-grained sand, clay, and silt particles. These particles include Fe-shale and graywacke geochemical characteristics. Their plagioclase index of alteration, chemical index of weathering, chemical index of alteration, and other weathering index values, suggest that the studied sediments have likely undergone low to moderate weathering and alteration processes. The Th/U ratios generally indicated a lower distribution relatively to the upper continental crust, and they displayed slight enrichment in alkali elements, indicating a low degree of chemical weathering that has slightly influenced the sediment chemistry. Moreover, the Gd/Yb, Zr/Y, and La/Yb ratios exhibited similarities with the surrounding volcanic rocks on Robert Island. Additionally, their chondrite-normalized rare earth element (REE) patterns exhibited a similar trend, implying that the REE composition of the sediments is predominantly controlled by the local source rocks. Nevertheless, there were slight differences in the Y/Ho ratios and heavy REE (HREE) contents, suggesting the presence of additional sources contributing to the REE supply in the lake basins. The Co/Th, La/Sc, Th/Sc, and Zr/Sc ratios mostly resembled those of basic volcanic rocks, while the Rb, K, HREE, and Ni values dominantly indicated basic rocks with a minor input from felsic magmatic or quartzose sedimentary rocks. Considering the geomorphology and location of the basins, which are mostly situated along the coast where foehn winds have a limited influence over ice-free areas, it is likely that locally resuspended materials have had a significant impact. This factor may mask any potential signals of modern dust fallout and accumulation. However, possible dust sources include nearby or distant areas, such as exposed rock and sediment within the immediate vicinity of the lakes, including dry lakebeds, glacial outwash plains, or exposed moraines. Based on multiproxy element analyses, including REEs, high field strength elements, and lithophile elements, the geochemistry of the studied sediments, the overall geochemical characteristics cannot be fully explained by the local sources, suggesting that weathering processes and minor contributions from dust materials have played a nonnegligible role in shaping their chemistry. [ABSTRACT FROM AUTHOR]

Dismal Island is located at the entrance of Marguerite Bay between Adelaide Island to the northeast and Alexander Island to the southwest within the Antarctic Peninsula (AP). Its unique position between Alexander and Adelaide islands provides the opportunity to perform testing and link these regions through Cenozoic magmatism and tectonics due to the subduction of the Pacific plate beneath the AP along the northern margin. Dismal Island was visited in February 2021 within the framework of the sixth Turkish Antarctic Expedition (TAE-VI). Thirteen samples were collected for petrography, geochronology, and low-temperature thermochronology (LTT). Of the samples, 3 were dated using laser ablation-inductively coupled plasma-mass spectrometer zircon U-Pb geochronology, 2 were dated using apatite fission-track (AFT) analysis, and 1 was dated using apatite uranium-thorium-helium (U-Th/He) (AHe) thermochronology. The island comprises massif quartz-diorite, tonalite, mafic, and felsic dikes, indicating a hybrid magma source. The 3 zircon U-Pb ages yielded a crystallization age of 47-48 for the magmatic body. The AFT ages yielded a cooling age of 41 Ma, suggesting either a shallow emplacement at a depth of ~4 km or an uplift/exhumation during middle-late Eocene boundary. In contrast, the AHe age of 1 sample was 20.1 ± 1.1 Ma, together with a fast-cooling profile during the same period, which indicated an early Miocene uplift in the region. Similar early-middle Eocene crystallization ages within similar rock outcrops were determined on Adelaide and Alexander islands, Adelaide Island Intrusive Suite. The AFT ages obtained in this study (~41 Ma), close to formation age, were also found on Adelaide and Alexander islands. The (LTT) literature of the region shows that the LTT ages get younger to the north along the AP, reflecting the northward migration of the ridge-trench collision and opening of the slab window along the western coast of the AP. The AHe age and the fast-cooling profile suggested that the ridge-subduction between the Tula and Adelaide fracture zones to the north of Dismal Island reached the region during Aquitanian-Burdigalian. [ABSTRACT FROM AUTHOR]

The activity of people increased worldwide and has become an important source of disturbance to nesting birds even in a pristine environment of the polar regions. In this study, we focused on the correlation between disturbances and incubation behaviour of two Sterna species. By video surveillance of nests on low-disturbance and high-disturbance sites we evaluated (i) whether the incubation behaviour of Arctic terns Sterna paradisaea in Svalbard differed between various levels of mostly anthropogenic (passing people) disturbances and (ii) whether the incubation behaviour of Antarctic terns Sterna vittata on the Antarctic Peninsula differed between various levels of mostly natural (predators) disturbances. We analysed whole-day continuous recordings (median length > 24 h) of 72 nests from four study sites. Incubation behaviour at high-disturbance sites was characterized by lower nest attentiveness, shorter on-bouts, and recurrent interruptions, whilst off-bout length remained mostly unchanged. The total time spent sleeping and average sleep-bout length were shorter, whilst the frequency of visual inspection of the surroundings was higher at high-disturbance sites. In all, the responses of incubating terns to human disturbance did not exceed those induced by native predators. The behavioural responses, as measured by the direction and size of effects, were remarkably consistent for both species, representing the two polar regions with different natural predation risks as well as a different history of human impacts. Unless there are specific long-term costs associated with human disturbance that we cannot evaluate here, the coexistence of people and breeding terns might be sustainable even in the polar regions. [ABSTRACT FROM AUTHOR]

The Antarctic Peninsula is one region that has recently experienced warming substantially more rapidly than the global mean over the past 50 years. Marian Cove is located in the South Shetland Islands connected to the Bransfield Strait via Maxwell Bay between King George Island and Nelson Island. In this study, we identified properties and mechanisms of seawater exchange in Marian Cove from multiple hydrographic surveys and a single bottom‐mounted mooring installed at the entrance to Marian Cove. Regardless of the season, the mean current velocity profiles at the entrance to Marian Cove were constant because of the influence of tidal forcing. Wind was the primary force that determined the variation in surface current; in response, a countercurrent occurred near the bottom area. We estimated salt transport to understand what effects Maxwell Bay′s saline water intrusion has on the Marian Cove environment. When the daily easterly wind was at its maximum of 18.5 m s−1, the salinity could increase to 7.20 × 10−4 g kg−1 in 1 day. In addition, the average freshwater residence time in Marian Cove for the quantitative evaluation of seawater exchange was approximately 9 days. However, the freshwater residence time was reduced to less than 2 days when there were extreme easterly winds. Plain Language Summary: In recent years, the Antarctic Peninsula has warmed up much faster than the global average. In the South Shetland Islands, Marian Cove is a small bay that connects to the Bransfield Strait through Maxwell Bay, which is between King George Island and Nelson Island. In this study, we used continuous observation devices at the entrance to Marian Cove to figure out how and why the seawater changes. Regardless of the season, inflow from the open sea occurs near the bottom due to the interaction of tides and friction forces. Wind was the main thing that changed the surface current, and as a result, the bottom current went in the opposite direction. We figured out how salt moves in Marian Cove, and the main thing that speeds up salt intrusion in Marian Cove is easterly wind. We try to estimate how long the water in Marian Cove stays there. On average, water can stay for about 9 days. However, when there were very strong easterly winds, the time was reduced to less than 2 days, which will be insufficient for phytoplankton growth. Key Points: Tide‐induced mean current was the primary factor sustaining mean seawater exchange at the entrance to Marian CoveSeawater exchange was mainly affected by wind forcingFreshwater residence time of Marian Cove was approximately 9 days and could be reduced to within 2 days by strong easterly winds [ABSTRACT FROM AUTHOR]

Brown Skua (Stercorarius antarcticus-lonnbergi) and South Polar Skua (Stercorarius maccormicki) occur throughout the Antarctic Peninsula and are sympatric in distribution over 500 km. In this region, hybridization between a male South Polar Skua and a female Brown Skua producing viable and fertile offspring. The present study aims to review the evolutionary history of South Polar Skua and Brown Skua to understand the hybridization process between these species better. To assess the evolutionary history between these species, 67 DNA samples were sequenced for AK1 locus, 70 samples for RAG1 locus, and 96 samples for Cytb locus, from individuals sampled at King George Island and Elephant Island. Cytb and RAG1 loci showed greater genetic diversity in samples from hybrid birds than those of non-hybrid individuals and may reflect the outcome of the heterosis. Overall, Brown Skua had higher genetic diversity than South Polar Skua. In addition, South Polar Skua showed probable populational expansion signals, in contrast to Brown Skua which showed population stability through time. However, our phylogenetic analysis did not corroborate the reciprocal monophyly between these species. Thus, South Polar Skua and Brown Skua show incomplete lineage sorting, indicating these species are a single taxonomic group. [ABSTRACT FROM AUTHOR]

Gentoo Penguin (Pygoscelis papua) is a species that reproduces in Antarctica and sub-Antarctic islands. During 2022 a Gentoo Penguin with an unusual plumage coloration was recorded at Esperanza/Hope Bay, north of the Antarctic Peninsula (63°24′ S, 57°01′ W). The coloring of plumage is achieved by two types of pigments known as carotenoids and melanins. Two different types of melanin (phaeomelanin and eumelanin) are responsible of producing different pigmentation patterns that oscillates between reddish-blackish coloration. The unusual coloration of the penguin was identified as melanism, a genetic condition that causes an excess of melanin pigment in feathers. This particular individual appeared to be in good health and exhibited normal behavior. As far as we know this is the second official report of melanism for the species since the first one in 1997 and it is the first report for the colony. [ABSTRACT FROM AUTHOR]

Abstract The oceans play an important role in mitigating climate change by acting as large carbon sinks, especially at high latitude regions. The Southern Ocean plays a major role in the global carbon dioxide (CO2) budget. This work aims to investigate the behavior of turbulent CO2 fluxes and quantify it under different atmospheric and oceanic conditions in the Drake Passage and Bransfield Strait regions on high spatiotemporal resolutions when compared with traditional CO2 fluxes estimations. The atmospheric stability condition was used to corroborate the description of CO2 fluxes. In situ, satellite, and reanalysis data from 08 to 22 November 2018, were used in this work. The Bransfield Strait uptaked 38.59% more CO2 than the Drake Passage due to the cold and fresh waters, allied to the influence of glacial meltwater dilution. Which increased the CO2 solubility, directing the CO2 fluxes to the ocean. The Bransfield Strait had predominantly stable atmospheric conditions, which contributed to this region acting as a CO2 sink. The Drake Passage, on average, behaved as a CO2 sink, mainly due to physical characteristics. This research contributes to a better understanding of the Southern Ocean’s role in the global carbon balance on scales that are very difficult to monitor.

Osteohistological studies allow us to obtain valuable information on different aspects related to the bone microstructure, physiology and ecology of organisms. Although the anatomy and morphology of penguin bones are well known, studies in osteohistology are still insufficient. In order to analyze the osteohistological variations between male and female adults of Pygoscelis adeliae (Aves, Spheniscidae), histological sections were prepared from various bones including appendicular (humerus, radius, ulna, carpometacarpus, femur, tibiotarsus, tarsometatarsus) and axial (vertebral and sternal ribs) elements. The results indicate that all sections showed compact tissue with reduced or absent medullary cavities and high bone density due to internal tissue compaction. Histologically, we identified three distinct tissue regions based on their bone matrix, vascular channels organization and compactions degree. Our results indicate osteohistological variations between sexes throughout the whole skeleton, including the first definitive evidence of medullary bone in the Sphenisciformes females. While the male specimen exhibited a medullary cavity characterized by an inner circumferential layer, the female displayed a medullary region without an inner circumferential layer, lower bone compaction, presence of medullary bone in all the sections, and greater development of intertrabecular spaces. These results are consistent with previous reports of medullary bone in females from other birds and provided an auxiliary criterion for sex differentiation. [ABSTRACT FROM AUTHOR]

The Antarctica Peninsula (AP) has experienced more frequent and intense surface melting recently, jeopardizing the stability of ice shelves and ultimately leading to ice loss. Among the key phenomena that can initiate surface melting are atmospheric rivers (ARs) and leeside foehn; the combined impact of ARs and foehn led to moderate surface warming over the AP in December 2018 and record‐breaking surface melting in February 2022. Focusing on the more intense 2022 case, this study uses high‐resolution Polar WRF simulations with advanced model configurations, Reference Elevation Model of Antarctica topography, and observed surface albedo to better understand the relationship between ARs and foehn and their impacts on surface warming. With an intense AR (AR3) intrusion during the 2022 event, weak low‐level blocking and heavy orographic precipitation on the upwind side resulted in latent heat release, which led to a more deep‐foehn like case. On the leeside, sensible heat flux associated with the foehn magnitude was the major driver during the night and the secondary contributor during the day due to a stationary orographic gravity wave. Downward shortwave radiation was enhanced via cloud clearance and dominated surface melting during the daytime, especially after the peak of the AR/foehn events. However, due to the complex terrain of the AP, ARs can complicate the foehn event by transporting extra moisture to the leeside via gap flows. During the peak of the 2022 foehn warming, cloud formation on the leeside hampered the downward shortwave radiation and slightly increased the downward longwave radiation. Plain Language Summary: On the Antarctic Peninsula (AP), when ice shelves break up, glaciers flow faster from the land into the sea, leading to ice loss and increasing sea level rise. Surface warming is projected to double by 2050 over Antarctica and may have led to ice shelf collapse. Two phenomena that enhance surface warming are atmospheric rivers, (long corridors of moisture in the atmosphere) and leeside foehn effects (cooler and moist air advection on the upwind side that becomes warmer and drier when descending on the leeside). Here we study two combined atmospheric river and foehn events that led to surface warming on the AP, occurring in December 2018 and February 2022. The main warming mechanism in the northeastern AP during the nighttime was transfer of heat from the air to the ice surface (sensible heat flux), while the main mechanism during the daytime was intense sunlight, which was able to reach the surface because of clear skies on the opposite (lee) side caused by foehn. However, complicating the picture, there are gaps in the AP mountain range that let the atmospheric river through, allowing clouds to form on the other side, which then blocked some of the sunlight. Key Points: This study investigates the atmospheric river and foehn warming over the Antarctic Peninsula via observations and model simulationsAtmospheric rivers led to stronger precipitation on the upwind side and favored the foehn‐related sensible heat transfer on the leesideUnder the combined atmospheric rivers and foehn, shortwave radiation contributed the most to the ice surface warming, followed by sensible heat flux [ABSTRACT FROM AUTHOR]

Abstract—A method is proposed for constructing a regional algorithm to calculate the thickness of the euphotic zone from in situ measurements of the vertical profiles of the beam attenuation coefficient under the condition of one-parameter optical properties of water (Case-1 water). Using the proposed methodology, a regional algorithm for determining the thickness of the photic zone was developed based on the results of synchronous measurements of the beam attenuation coefficient and photosynthetically active radiation, performed in January 2022 as part of cruise 87 of the R/V Akademik Mstislav Keldysh for the northwestern Weddell Sea. For this region, an equation was obtained that can estimate the depth of the photic zone with a relative reconstruction error of 18%. [ABSTRACT FROM AUTHOR]

Active continental margins are tectonic sites with complex sedimentary processes. Tectono–sedimentary interactions occur over geological time and determine the modern morphology of the margin. However, such interactions have been poorly documented in high‐latitude regions. This study focuses on deep‐water sedimentary systems on the South Shetland convergent margin, which is the only remaining active continental margin in Antarctica. Numerous gullies, 20 canyons and three contourite drifts are identified by interpreting bathymetry, oceanography and reflection seismic data. Heavy mineral contents of a gravity core, located at a downslope elongated mounded drift, show the asynchronous interplay of downslope and alongslope processes. The rest of the margin is dominated by turbidity currents. Variations in the slope gradient control thalweg profiles and sinuosity of canyons. Tectonic‐related morphology restricts the distribution of contourite drifts. Earthquakes triggered by underplating and tectonic compression may induce slope instability at the lower flank of the plastered drift. Tectonic uplift influences the amount of sediments transported by ice sheets and controls the shelf stacking pattern. The mixed turbidite–contourite system transitions to separated canyon and drift systems from passive to active continental margins under the influence of the tectonic‐related morphology. A systematic comparison has been made among several convergent margins with similar tectonic settings. Results suggest that submarine canyons on these shelf‐slope systems have similar morphological features and are comparable in size. Coarse sediment input and steep continental slopes (mean slope 7 to 10°) control the canyon morphology on these margins. Therefore, this research has important implications for furthering the current understanding of sedimentary systems on high‐latitude convergent margins and tectono–sedimentary interactions. [ABSTRACT FROM AUTHOR]

In the second half of the 20th century, the western Antarctic Peninsula recorded the highest mean annual air temperature rise in the Antarctic. The South Shetland Islands are located about 100 km northwest of the Antarctic Peninsula. The mean annual air temperature at sea level in this Maritime Antarctic region is close to −2 °C and, therefore, very sensitive to permafrost degradation following atmospheric warming. Among geomorphological indicators of permafrost are rock glaciers found below steep slopes as a consequence of permafrost creep, but with surficial movement also generated by solifluction and shallow landslides of rock debris and finer sediments. Rock glacier surface velocity is a new essential climate variable parameter by the Global Climate Observing System, and its historical analysis allows insight into past permafrost behavior. Recovery of 1950s aerial image stereo-pairs and structure-from-motion processing, together with the analysis of QuickBird 2007 and Pleiades 2019 high-resolution satellite imagery, allowed inferring displacements of the Hurd rock glacier using compression ridge-and-furrow morphology analysis over 60 years. Displacements measured on the rock glacier surface from 1956 until 2019 were from 7.5 m to 22.5 m and surface velocity of 12 cm/year to 36 cm/year, measured on orthographic images, with combined deviation root-mean-square of 2.5 m and 2.4 m in easting and northing. The inferred surface velocity also provides a baseline reference to assess today's displacements. The results show patterns of the Hurd rock glacier displacement velocity, which are analogous to those reported within the last decade, without being possible to assess any displacement acceleration. [ABSTRACT FROM AUTHOR]

The Antarctic Peninsula and adjacent region is one of the planet's fastest warming areas and has experienced remarkable environmental change. Planktonic ciliates are sensitive to environmental change because of their short lifespans and limited mobility. However, not much research has been done on the distribution of planktonic ciliates and their relation to environmental factors in waters around the Antarctic Peninsula and the South Orkney Plateau. Here, we investigated planktonic ciliate distribution in different areas of the Antarctic Peninsula and the South Orkney Plateau region during 26 December 2015 and 11 January 2016. Tintinnids made up less than 10% and 15% of total planktonic ciliate abundance and biomass, respectively. Aloricate ciliates and tintinnids showed different vertical profiles, indicating their different responses to environmental change. In the Bransfield Strait, tintinnids mainly occurred in the south side of the strait. In the South Orkney Plateau with well-stratified water column, Laackmanniella naviculaefera occurred in the surface 0–25-m Summer Surface Water (SSW), while Cymatocylis cf. cristallina occurred in the 50–150-m Winter Water. Along a transect between the Central Basin and Eastern Basin, warmer Antarctic Circumpolar Current waters intruded southward and overlay the SSW of the Weddell Sea confluence. Consequently, L. naviculaefera was suppressed into deeper water than in the South Orkney Plateau. This study showed that the characteristic hydrography of the Antarctic Peninsula and the South Orkney Plateau shaped the distribution patterns of planktonic ciliates. Our results are helpful for understanding the future dynamics of pelagic ecosystems in this rapidly changing area. [ABSTRACT FROM AUTHOR]

Previously, only three Candelariella species were known from Antarctica: C. aurella, C. flava and C. vitellina. After morphologically and phylogenetically examining our collections on soil from James Ross Island, located in the north-east Antarctic Peninsula region, and Horseshoe Island, a small rocky island in Bourgeois Fjord, Marguerite Bay in the south-west Antarctic Peninsula, we describe the lichen species Candelariella ruzgarii as new to science. Sequences of the nrITS, mtSSU and RPB1 gene regions of the new species were amplified and revealed that the phylogenetic position of the new species is in the C. aurella group, which is characterised by 8-spored asci and ± granular thalli. Candelariella ruzgarii is phylogenetically most closely related to C. aurella s. lat. but differs mainly in ecology as the new species grows on soil or on terricolous lichens, whereas the latter species grows on calcareous rocks, rarely on wood. Morphologically, C. ruzgarii is very similar to C. aggregata, a Northern Hemisphere species that grows on mosses and plant debris. Apart from the different phylogenetical position, C. ruzgarii has a thicker and sometimes slightly crenulated thalline margin and somewhat shorter ascospores than C. aggregata. We also report C. plumbea for the first time from Antarctica, a species with a thick and grey thallus that was previously known from Europe and Asia.

Aerial frames and satellite imagery are widely recognized data sources from which to produce maps. For volcanoes, maps enable the quantification of erupted ash and the destruction caused. The last eruptive sequence on Deception Island was endured from 1967 to 1970. Analogue maps were produced via classical photogrammetric methods with a high degree of human intervention mainly to analyse the volcanic-centres areas only. However, historical aerial frames cover the whole of Deception Island. Structure from motion photogrammetry, a near-automated compilation of digital image processing strategies, minimizes the degree of human intervention to produce orthographic mosaics and digital elevation models from digital aerial frames. Orthographic mosaics were produced from historical aerial frames of 1956 and 1968, and a Kompsat-3 image of 2020. Their shared root-mean-square deviation was 1.8 m and 1.7 m in easting and northing, respectively, at ground control points measured with phase-differential global navigation satellite systems. The digital elevation models were processed with a root-mean-square deviation of 2.3 m and 3.6 m from 1956 and 1968 aerial frames, respectively. As the first application, erupted ashfall and the subsequent destruction, mainly at the former Chilean and British bases, were identified, and the volume of erupted ash was assessed to be over 0.16 km3 within the area mapped by these new digital cartographic products. [ABSTRACT FROM AUTHOR]

In this study, we obtained samples through stomach lavage to determine the diet of Adelie Penguins Pygoscelis adeliae during the guard and crèche periods at Hope/Esperanza Bay, Antarctica, during four breeding seasons (2014-2019, except 2016). Antarctic krill was the dominant prey, contributing > 99.6% of the diet by mass. The remainder of prey were fish, amphipods, and mollusks. Among fish, the nototheniid Pleuragramma antarcticum was the most frequent while the bathydraconid Parachaenichthys charcoti dominated by mass. Mollusks and fish increased their contribution during the crèche period in accord with seasonal patterns elsewhere. [ABSTRACT FROM AUTHOR]

The western Antarctic Peninsula (WAP) is a climatically sensitive region where foundational changes at the basis of the food web have been recorded; cryptophytes are gradually outgrowing diatoms together with a decreased size spectrum of the phytoplankton community. Based on a 11‐year (2008–2018) in‐situ dataset, we demonstrate a strong coupling between biomass accumulation of cryptophytes, summer upper ocean stability, and the mixed layer depth. Our results shed light on the environmental conditions favoring the cryptophyte success in coastal regions of the WAP, especially during situations of shallower mixed layers associated with lower diatom biomass, which evidences a clear competition or niche segregation between diatoms and cryptophytes. We also unravel the cryptophyte photo‐physiological niche by exploring its capacity to thrive under high light stress normally found in confined stratified upper layers. Such conditions are becoming more frequent in the Antarctic coastal waters and will likely have significant future implications at various levels of the marine food web. The competitive advantage of cryptophytes in environments with significant light level fluctuations was supported by laboratory experiments that revealed a high flexibility of cryptophytes to grow in different light conditions driven by a fast photo‐regulating response. All tested physiological parameters support the hypothesis that cryptophytes are highly flexible regarding their growing light conditions and extremely efficient in rapidly photo‐regulating changes to environmental light levels. This plasticity would give them a competitive advantage in exploiting an ecological niche where light levels fluctuate quickly. These findings provide new insights on niche separation between diatoms and cryptophytes, which is vital for a thorough understanding of the WAP marine ecosystem. [ABSTRACT FROM AUTHOR]

The Southern Ocean and coastal Antarctica provide a variety of ecosystem services with benefits for humankind that are of regional and global importance. Despite being nearly uninhabited, increasing exploitation of natural resources, a growing human presence, and environmental change threaten the sustained provisioning of these services. Ecosystem service assessments have proven as a suitable tool to understand the relevance of ecosystems for human well-being and guide decision-making, but the fluid and transboundary nature of marine ecosystems poses challenges to analyzing ecosystem services in regions with large marine sections. New methods to objectively assess the supply of ecosystem services for such realms are needed, and this need is exemplified by the Antarctic Peninsula region which encompasses rich marine, coastal, and terrestrial ecosystems but faces growing impacts and needs for taking action. In this study we applied the matrix method, an expert-based approach that employs a tabular matrix of ecosystem services and service providing units (SPUs) to elicit expert knowledge and rate the actual supply of key ecosystems services from the Antarctic Peninsula region. Further, we tested the applicability of this method on conventional definitions of SPUs and on objectively defined physico-chemical seascape units for a subset of the study region. Our results show high variations in the estimated supply of ecosystem services for the Antarctic Peninsula region, both with respect to the applied data models and in terms of the assessed services. While cultural and regulating services received highest supply estimates, provisioning services were regarded less relevant for the study region. Further, experts' supply estimates were much lower for the tested physico-chemical seascape units than for bathymetrically regionalized marine areas. The results suggest that a more explicit elaboration of linkages between ecosystem functions and processes and of the actual supply of ecosystem services is required in order to tap the full potential of such seascape data models in the context of qualitative, expert-based ecosystem service assessments.

The Southern Ocean and coastal Antarctica provide a variety of ecosystem services with benefits for humankind that are of regional and global importance. Despite being nearly uninhabited, increasing exploitation of natural resources, a growing human presence, and environmental change threaten the sustained provisioning of these services. Ecosystem service assessments have proven as a suitable tool to understand the relevance of ecosystems for human well-being and guide decision-making, but the fluid and transboundary nature of marine ecosystems poses challenges to analyzing ecosystem services in regions with large marine sections. New methods to objectively assess the supply of ecosystem services for such realms are needed, and this need is exemplified by the Antarctic Peninsula region which encompasses rich marine, coastal, and terrestrial ecosystems but faces growing impacts and needs for taking action. In this study we applied the matrix method, an expert-based approach that employs a tabular matrix of ecosystem services and service providing units (SPUs) to elicit expert knowledge and rate the actual supply of key ecosystems services from the Antarctic Peninsula region. Further, we tested the applicability of this method on conventional definitions of SPUs and on objectively defined physico-chemical seascape units for a subset of the study region. Our results show high variations in the estimated supply of ecosystem services for the Antarctic Peninsula region, both with respect to the applied data models and in terms of the assessed services. While cultural and regulating services received highest supply estimates, provisioning services were regarded less relevant for the study region. Further, experts' supply estimates were much lower for the tested physico-chemical seascape units than for bathymetrically regionalized marine areas. The results suggest that a more explicit elaboration of linkages between ecosystem functions and processes and of the actual supply of ecosystem services is required in order to tap the full potential of such seascape data models in the context of qualitative, expert-based ecosystem service assessments.

There are only two species of native vascular plants found on the Antarctic Peninsula and the surrounding islands, Deschampsia Antarctica, and Colobanthus quitensis. Poa annua, a successful invasive species, poses a threat to D. antarctica and C. quitensis. This region may experience extreme changes in biodiversity due to climate change over the next 100 years. This study explores the relationship between vascular vegetation and changing temperature on the Antarctic Peninsula and uses a systems modelling approach to account for three climate change scenarios over a 100-year period. The results of this study indicate that (1) D. antarctica, C. quitensis, and P. annua will likely be impacted by temperature increases, and greater temperature increases will facilitate more rapid species expansion, (2) in all scenarios D. antarctica species occurrences increase to higher values compared to C. quitensis and P. annua, suggesting that D. antarctica populations may be more successful at expanding into newly forming ice-free areas, (3) C. quitensis may be more vulnerable to the spread of P. annua than D. antarctica if less extreme warming occurs, and (4) C. quitensis relative growth rate is capable of reaching higher values than D. antarctica and P. annua, but only under extreme warming conditions.

Accurate species identification is essential to assess biodiversity and species richness in ecosystems threatened by rapid and recent environmental changes, such as warming in most Antarctic waters. The Lepidonotothen species complex comprises demersal notothenioid fishes which inhabit the shelf areas of the Antarctic Peninsula, the Scotia Arc and sub‐Antarctic islands with a circum‐Antarctic distribution. Species determination in this group has often been problematic. In particular, whether Lepidonotothen squamifrons and Lepidonotothen kempi are valid as separate species has been questioned. In this study, we analysed the genetic variation among four nominal southern polar species within this complex (L. kempi, L. squamifrons, Nototheniops larseni, Nototheniops nudifrons) by means of three different markers (ND2 and tRNA mitochondrial genes and a panel of 16 nuclear microsatellites). We tested whether individuals morphologically assigned to L. kempi showed genetic separation from L. squamifrons. Our analyses indicated a lack of differentiation between L. kempi and L. squamifrons. However, a genetically distinct population was found for L. squamifrons at the Shag Rocks islands near South Georgia. Antarctic and sub‐Antarctic islands are known to be home to many cryptic species and further studies will elucidate if the genetically differentiated population we found potentially originated from this context and can be considered an incipient species. Our analysis contributes to further characterize the species composition of the most abundant fish suborder in the Southern Ocean, which is among the regions most threatened by climate change. [ABSTRACT FROM AUTHOR]

The bulk of the chinstrap penguin (Pygoscelis antarcticus) global population inhabits the Antarctic Peninsula and Scotia Sea, which is a region undergoing rapid environmental changes. Consequently, regional level decreases for this species are widespread. This study aimed to evaluate the level of breeding colony changes in the Antarctic Peninsula and South Orkney Islands, which, roughly, hold 60% of the global chinstrap penguin population. The results indicated that within a period of 40 to 50 years, 62% of colonies underwent decreases, and the majority of colonies experienced decreases over 50%, which is represented by numbers in the range of 2000 to 40,000 pairs. Within three generations' time, the whole population for the area had experienced decreases of around 30%. These levels of decrease add to the fact that the suspected causes are not likely reversible in the short- to mid-term, calling for increased concern about the conservation of this species. [ABSTRACT FROM AUTHOR]

Krill and salps play a pivotal role in marine food webs and ocean biogeochemistry, yet little is known about their stoichiometry, which is crucial for our understanding of the consequences of key grazer population shifts for ecosystem functioning. To assess differences in stoichiometric requirements, we compared the elemental composition of carbon (C), nitrogen (N) and phosphorus (P) in body tissue and gut content of Euphausia superba and Salpa thompsoni collected along the Northern Antarctic Peninsula and conducted a systematic literature review on the stoichiometry of 33 euphausiid and 19 salp species. Our data revealed significantly lower body C:P and N:P ratios but higher gut content N:P in S. thompsoni compared with E. superba , suggesting higher P uptake. In contrast, literature data showed higher C:N, C:P and N:P ratios in salps, potentially indicating lower nutrient demand compared with krill. However, literature data exhibited high intra- and interspecific variability potentially driven by organism size, seasonal or latitudinal variations, emphasizing that nutritional requirements are not only related to the target species, but also to its habitat. Our study provides valuable stoichiometric information for future experimental and modeling studies, fostering our ability to predict the future role of krill and salps for ocean biogeochemistry. [ABSTRACT FROM AUTHOR]

We assessed satellite‐retrieved marine aerosol in the western Antarctic Peninsula (WAP) across a 12‐year period from coarse‐mode aerosol optical depth (AODC), often used as a proxy for sea spray aerosol (SSA), and marine aerosol optical depth (MAOD), a newly developed proxy for tropospheric marine aerosol. Across open ocean to coastal regions, daily fluctuations in nighttime and daytime winds, respectively, drove increasing MAOD and AODC. MAOD depicted strong correlations with wind speed across open ocean and weak correlations in coastal regions. In the open ocean, AODC exhibited a very weak significant correlation to wind speed and a weak significant correlation to sea surface temperature (SST). We thus observed that warmer SST enhanced the production of SSA, supporting prior studies. This is the first study to assess patterns of AODC in the WAP. In contrast to the tropical Pacific, seasonal patterns showed that biological activity likely contributed toward MAOD and AODC magnitudes. Plain Language Summary: The production of marine aerosol in the Bellingshausen Sea of the western Antarctic is coupled to the environment. Processes driving marine aerosol include wind speed, which produces sea spray aerosol (SSA), sea surface temperature (SST), which can enhance the production of SSA, and seasonal dynamics of sea ice melt and phytoplankton blooms, which can contribute to production of biogenic sources of marine aerosol. To study these drivers in closer detail, we used two specialized proxies of marine aerosol concentration: coarse‐mode Aerosol Optical Depth (AODC), a proxy for SSA, and Marine Aerosol Optical Depth (MAOD) a proxy for low‐altitude marine aerosol. We examined MAOD and AODC from 2007 to 2018 and found that wind speed was a driver of day‐to‐day fluxes in marine aerosol. In contrast to the tropical Pacific in which enhanced biological activity suppresses SSA particle production, we did not observe lessening of MAOD and AODC magnitudes during the biologically productive austral summertime. In fact, summertime MAOD exhibited a weak significant correlation to daily wind speed in the coastal ocean despite a lack of significance in wintertime. This work enriches our knowledge of biotic and abiotic drivers of marine aerosol in high‐latitude environments. Key Points: The open ocean and coastal Bellingshausen Sea show weak correlations of marine aerosol optical depth (MAOD) to daily windsAODC exhibits weak correlations to sea surface temperature (SST) in the open ocean and very weak correlations to daily wind speed across all regionsSeasonal increases in MAOD dependence on daily wind speed is likely associated with higher biological activity in summer [ABSTRACT FROM AUTHOR]

We applied multi–temporal 1D magnetotelluric (MT) surveys to identify space–time anomalies of apparent resistivity ( ρ a ) in the upper lithosphere in the Antarctic Peninsula (the border between the Antarctic and the Shetland plates). We used time series over several weeks of the natural Earth's electric and magnetic fields registered at one MT station of the Universidad Nacional de Colombia (RSUNAL) located at Seymour–Marambio Island, Antarctica. We associated resistivity anomalies with contrasting earthquake activity. Anomalies of ρ a were detected almost simultaneously with the beginning of a seismic crisis in the Bransfield Strait, south of King George Island (approximately 85.000 events were reported close to the Orca submarine volcano, with focal depths < 20 km and MWW < 6.9). We explained the origin of these anomalies in response to fluid migration near the place of the fractures linked with the seismic swarm, which could promote disturbances of the pore pressure field that reached some hundreds of km away. [ABSTRACT FROM AUTHOR]

Plate reconstructions provide basic constraints on the tectonic evolution of the Antarctic Peninsula but they are limited by a scarcity of paleomagnetic data. Here, using a combination of new and published paleomagnetic data and geological evidence, we present an updated reconstruction of the plate rotation and spatio‐temporal history of magmatism of the northern Antarctic Peninsula since ∼90 Ma. The Phoenix Plate‐Antarctic Peninsula convergence variation and back‐arc extension of the Scotia Plate are correlated to five distinct plate rotation periods. The initiation of the ancestral South Sandwich subduction zone and the late Paleocene separation between the Antarctic Peninsula and South America may be explained by the small‐ and large‐scale clockwise rotation of the Antarctic Peninsula starting at ∼80 and 62 Ma, respectively. Furthermore, we have identified five pulses of magmatism, which are correlated to the Phoenix Plate‐Antarctic Peninsula convergence rates. The Antarctic Peninsula plate rotation fits well with the process observed in the Phoenix Plate subduction, long‐term variation of the magmatism and tectonic evolution in the Scotia Sea, clarifying the relationship between these geological events. Plain Language Summary: In this study, we update the northern Antarctic Peninsula‐South Shetland Islands plate rotation process since ∼90 Ma. Five new enhanced magmatic events are identified in the northern Antarctic Peninsula‐South Shetland Islands, and we also reconstruct the migration of magmatism. Then, we compare plate rotation and magmatic migration to the Phoenix Plate‐Antarctic Peninsula convergence, and find a strong correlation between these events. The abrupt change in the convergence rate is attributed to the enhanced magmatic events. The clockwise rotation of the northern Antarctic Peninsula also corresponds to the Late Cretaceous initiation of the ancestral South Sandwich subduction zone and the late Paleocene separation of the northern Antarctic Peninsula from South America, indicating a causal relationship. The counterclockwise rotation of the northern Antarctic Peninsula after ∼47 Ma facilitated lithospheric extension and basin opening in the South Scotia Ridge region, contributing to the opening of the Scotia Sea. Therefore, this study provides a comprehensive interpretation of the geological process in Scotia Sea regions, from slab subduction and overlaying plate rotation to magmatic evolution and continental separation. Key Points: We provide an updated reconstruction of the plate rotation and magmatic process of the northern Antarctic Peninsula since ∼90 MaThe relationship between Phoenix Plate subduction, northern Antarctic Peninsula plate rotation, and magmatic migration is reconstructedThe northern Antarctic Peninsula's plate rotation is linked to Weddell Sea crust subduction and the late Paleocene opening of the Scotia Sea [ABSTRACT FROM AUTHOR]

To understand the main orographic and non‐orographic sources of gravity waves (GWs) over South America during an Experiment (Rapp et al., 2021, https://doi.org/10.1175/BAMS-D-20-0034.1), we propose the application of a rotational spectral analysis based on methods originally developed for oceanographic studies. This approach is deployed in a complex scenario of large‐amplitude GWs by applying it to reanalysis data. We divide the atmospheric region of interest into two height intervals. The simulations are compared with lidar measurements during one of the flights. From the degree of polarization and the total energy of the GWs, the contribution of the upward and downward wave packets is described as a function of their vertical wavenumbers. At low levels, a larger downward energy flux is observed in a few significant harmonics, suggesting inertial GWs radiated at polar night jet levels, and below, near to a cold front. In contrast, the upward GW energy flux, per unit area, is larger than the downward flux, as expected over mountainous areas. The main sub‐regions of upward GW energy flux are located above Patagonia, the Antarctic Peninsula and only some oceanic sectors. Above the sea, there are alternating sub‐regions dominated by linearly polarized GWs and sectors of downward GWs. At the upper levels, the total available GW energy per unit mass is higher than at the lower levels. Regions with different degrees of polarization are distributed in elongated bands. A satisfactory comparison is made with an analysis based on the phase difference between temperature and vertical wind disturbances. Plain Language Summary: Atmospheric gravity waves (GWs) are of great importance in the transport of energy and momentum through the atmosphere. Their sources can be broadly classified as stationary and non‐stationary. The southern tip of South America represents one of the most important natural laboratories for detecting the coexistence of large‐amplitude GWs. We present a spectral method to establish a semi‐quantitative classification of the different groups of GWs and their main vertical direction of propagation. We apply the method on the basis of global model data. We divide the lower and middle atmosphere into two vertical intervals and compare the model with data from one of the instruments deployed during the experiment. Based on the direction of rotation of the vector defined by the GW oscillations of the two horizontal wind components, we describe the net contribution of the upward and downward wave packets as a function of their spectral harmonics. The main sub‐regions of upward GW energy flux alternate with sub‐regions dominated by linearly polarized GWs and downward GW sectors mainly above the ocean. At the upper levels, the total available GW energy per unit mass is higher than at the lower levels. A comparison is made between these results and an independent analysis based on the known polarization relations for GWs. Key Points: A rotary spectral analysis is proposed to classify possible sources of gravity waves (GWs) according to their degree of polarizationFrom reanalysis data, the method is applied at a selected position during one of the flights of the SOUTHTRAC‐GW ExperimentUpward and downward GW structures from orographic and non‐orographic origin with different degrees of polarization are observed [ABSTRACT FROM AUTHOR]