British Antarctic Survey

During austral winter, the southern high latitudes has some of the most intense stratospheric gravity wave (GW) activity globally. However, producing accurate representations of GW dynamics in this region in numerical models has proved exceptionally challenging. One reason for this is that questions remain regarding the relative contributions of orographic and non‐orographic sources of GWs here. We use three‐dimensional (3‐D) satellite GW observations from the Atmospheric Infrared Sounder in austral winter 2012 in combination with the Gravity‐wave Regional Or Global Ray Tracer to backward trace GW rays to their sources. We trace over 14.2 million rays, through ERA5 reanalysis background atmosphere, to their lower atmospheric sources. We find that GWs observed thousands of km downstream can be traced back to key orographic regions, and that on average, all waves (orographic and non‐orographic) converge meridionally over the Southern Ocean. We estimate that across this winter, orographic sources contribute around ∼ ${\sim}$ 5%–35% to the total momentum flux (MF) observed near 60° ${}^{\circ}$S. The remaining proportion consists of waves from non‐orographic sources, which although typically carry lower MF, the large spatial extent of non‐orographic sources leads to a higher overall contribution. We also quantify the proportion of MF traced back to different regions across the whole southern high latitudes area in order to measure the relative importance of these different regions. These results provide the important insights needed to advance our knowledge of the atmospheric momentum budget in the southern high latitudes.

The Antarctic Circumpolar Current (ACC) is Earth's largest current flowing around Antarctica at all depths and connecting major ocean basins, thus representing an important component of Earth's climate. However, the timing and key controls determining ACC flow path and its strength as a function of past climatic boundary conditions that ultimately resulted in its modern configuration remain unclear due to major uncertainties in paleoceanographic and tectonic reconstructions. Here we present a unique high‐resolution laser ablation‐derived late Cenozoic seawater lead isotope record obtained from a hydrogenetic ferromanganese crust from the Pacific sector of the Southern Ocean. Our Pb isotope data reveal that the ACC has experienced five stable circulation states since the early Miocene which were separated by four major transitions observed at 17.5‐14.6, 12, 10 and 5 Ma. We suggest that the relatively abrupt transitions between ACC circulation state were mainly induced by tectonic changes, whereas the impact of climatic changes was of secondary importance. According to our data the modern ACC configuration formed 5 million years ago, likely in response to the closure of the Panama Seaway. Since the Drake Passage (DP) has already been an open seaway since at least the late Miocene, our results demonstrate that DP opening was not the only factor affecting past ACC circulation. Our data also show that changes in the latitudinal position of the ACC were linked to the middle Miocene waxing and waning of the Antarctic ice sheets, which emphasizes the ACC's critical role as a key control of Antarctic glaciation.

Drones are being increasingly used to monitor wildlife populations; their large spatial coverage and minimal disturbance make them ideal for use in remote environments where access and time are limited. The methods used to count resulting imagery need consideration as they can be time‐consuming and costly. In this study, we used a fixed‐wing drone and Beyond Visual Line of Sight flying to create high‐resolution imagery and digital surface models (DSMs) of six large king penguin colonies (colony population sizes ranging from 10,671 to 132,577 pairs) in South Georgia. We used a novel DSM‐based method to facilitate automated and semi‐automated counts of each colony to estimate population size. We assessed these DSM‐derived counts against other popular counting and post‐processing methodologies, including those from satellite imagery, and compared these to the results from four colonies counted manually to evaluate accuracy and effort. We randomly subsampled four colonies to test the most efficient and accurate methods for density‐based counts, including at the colony edge, where population density is lower. Sub‐sampling quadrats (each 25 m²) together with DSM‐based counts offered the best compromise between accuracy and effort. Where high‐resolution drone imagery was available, accuracy was within 3.5% of manual reference counts. DSM methods were more accurate than other established methods including estimation from satellite imagery and are applicable for population studies across other taxa worldwide. Results and methods will be used to inform and develop a long‐term king penguin monitoring programme.

The post-exploitation recovery of the south-west Atlantic southern right whale (SRW, Eubalaena australis ) population has been affected by widespread calf mortalities, resulting in the development of an International Whaling Commission Conservation Management Plan (IWC-CMP). The coastal waters around the Falkland Islands (Malvinas) comprise a recently documented wintering ground for the population. In July 2022, we deployed satellite tags on 10 SRWs to better understand their occurrence around the islands and their connectivity with other geographic regions. The animals remained in the islands for 1 to 57 d following tagging. High-use habitats comprised waters <10 km off the north and north-east coasts of East Falkland, where they exhibited slow and varied movements consistent with breeding and social behaviours. Six whales, including all 3 confirmed females, subsequently continued to the major calving ground located at Peninsula Valdés (Argentina), where they remained for up to 84 d. During spring, almost all tagged whales utilised the Patagonian Shelf (70-140 m depth) as a foraging habitat. Three males travelled south-east after departing the islands and variously visited higher latitude foraging grounds including the South Orkney and South Shetland islands, Scotia Sea and Antarctic Peninsula. Telemetry provided valuable information on the spatial and temporal extent to which SRWs aggregate in Falkland Islands (Malvinas) waters during winter and supports growing evidence that the region is a high-use critical habitat supporting breeding behaviour. The region should be incorporated into future region-wide conservation efforts for the south-west Atlantic SRW population and merits recognition in the IWC-CMP.

The Earth’s climate is a complex system including key components such as the Arctic Summer Sea Ice and the El Niño Southern Oscillation alongside climate tipping elements including polar ice sheets, the Atlantic Meridional Overturning Circulation, and the Amazon rainforest. Crossing thresholds of these elements can lead to a qualitatively different climate state, endangering human societies. The cryosphere elements are vulnerable at current levels of global warming (1.3 °C) while also having long response times and large uncertainties. We assess the impact of interacting Earth system components on tipping risks using an established conceptual network model of these components. Polar ice sheets (Greenland and West Antarctic ice sheets) are most decisive for tipping likelihoods and cascading effects within our model. At a global warming level of 1.5 °C, neglecting the polar ice sheets can alter the expected number of tipped elements by more than a factor of 2. This is concerning as overshooting 1.5 °C of global warming is becoming inevitable, while current state-of-the-art IPCC-type models do not (yet) include dynamic ice sheets. Our results suggest that polar ice sheets are critical to improving understanding of tipping risks and cascading effects. Therefore, improved observations and integrated model development are crucial.

Per-and polyfluoroalkyl substances (PFAS) are persistent anthropogenic contaminants, some of which are toxic and bioaccumulative. Perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs) can form during the atmospheric degradation of precursors such as fluorotelomer alcohols (FTOHs), N-alkylated perfluoroalkane sulfonamides (FASAs), and hydrofluorocarbons (HFCs). Since PFCAs and PFSAs will readily undergo wet deposition, snow and ice cores are useful for studying PFAS in the Arctic atmosphere. In this study, 36 PFAS were detected in surface snow around the Arctic island of Spitsbergen during January−August 2019 (i.e., 24 h darkness to 24 h daylight), indicating widespread and chemically diverse contamination, including at remote high elevation sites. Local sources meant some PFAS had concentrations in snow up to 54 times higher in Longyearbyen, compared to remote locations. At a remote high elevation ice cap, where PFAS input was from long-range atmospheric processes, the median deposition fluxes of C 2 − C 11 PFCAs, PFOS and HFPO−DA (GenX) were 7.6−71 times higher during 24 h daylight. These PFAS all positively correlated with solar flux. Together this suggests seasonal light is important to enable photochemistry for their atmospheric formation and subsequent deposition in the Arctic. This study provides the first evidence for the possible atmospheric formation of PFOS and GenX from precursors.

Biologging has been used on a range of wild animals to document spectacular feats of migration and behaviour. We describe the pursuit, capture, and ingestion of an adult Atlantic bluefin tuna (Thunnus thynnus) (175 cm, estimated weight: 81 kg), which was instrumented with a biologging tag, by a predator, most likely an orca (Orcinus orca). The predation event lasted over 19 min, with the tuna exhibiting elevated activity (max acceleration 3.12 g) and a rapid ascent from 126 m at 3.6 m.s− 1 followed by death and handling at the surface. Orca were separately recorded using video tags, capturing and handling tuna cooperatively in a manner consistent with the tuna data. We then present the longest orca accelerometry dataset from the ingested MiniPAT tag, with diel patterns of activity and 77 feeding events. These unique datasets provide insight into the energetic dynamics of two of the ocean’s fastest predators.

After the near-complete cessation of commercial whaling, ship collisions have emerged as a primary threat to large whales, but knowledge of collision risk is lacking across most of the world's oceans. We compiled a dataset of 435,000 whale locations to generate global distribution models for four globally ranging species. We then combined >35 billion positions from 176,000 ships to produce a global estimate of whale-ship collision risk. Shipping occurs across 92% of whale ranges, and <7% of risk hotspots contain management strategies to reduce collisions. Full coverage of hotspots could be achieved by expanding management over only 2.6% of the ocean's surface. These inferences support the continued recovery of large whales against the backdrop of a rapidly growing shipping industry.

Permafrost is a potentially important source of deglacial carbon release alongside deep-sea carbon outgassing. However, limited proxies have restricted our understanding in circumarctic regions and the last deglaciation. Tibetan Plateau (TP),the Earth's largest low-latitude and alpine permafrost region, remains underexplored. Using speleothem growth phases, we reconstruct TP permafrost thawing history over the last 500,000 years, standardizing chronology to investigateNorthern Hemisphere permafrost thawing patterns. We find that, unlike circumarctic permafrost, TP permafrost generally initiates thawing at the onset of deglaciations, coinciding with Weak Monsoon Intervals and sluggish Atlantic Meridional Overturning Circulation (AMOC) during Terminal Stadials. Modeling elaborates that the associated Asian monsoon weakening induces anomalous TP warming through local cloud–precipitation–soil moisture feedback. This, combined with high-latitude cooling, results in asynchronous boreal permafrost thawing. During the last deglaciation, however, anomalous AMOC variability delayed TP and advanced circumarctic permafrost thawing. Our results indicate that permafrost carbon release, influenced by millennial-scale AMOC variability, may have been a non-trivial contributor to deglacial CO 2 rise.

During a 2019 Chilean Antarctic Scientific Expedition (ECA 55) studying crustose coralline algae (CCA) diversity on the Antarctic Peninsula, bleaching of these algae was observed for the first time in this region. Here, we present initial findings on the physiological state of bleached and normally pigmented CCA ( Clathromorphum sp.) assessed using chlorophyll- a fluorescence induction pulse amplitude modulation. The study site experienced high light exposure and salinity in the water column. Our analyses found that bleached CCA have relatively healthy photophysiology responses but lower photosynthetic efficiency, which could be associated with the low salinities recorded in the study area. However, seasonal monitoring and mesocosm experiments across the southern polar latitudes are urgently required to confirm this hypothesis.

Visokoi is a small volcanic island in the remote South Sandwich Islands and is unique in being dominated by the basaltic andesite products of highly explosive eruptions. Here, its geology is described in detail for the first time and can be used to characterize the construction of an active glacierized volcano in an intra-oceanic volcanic arc setting. More than 90% of the volcano is submarine and is composed of (1) a ~ 2.5 km-high mound formed of pillow lava and tuff breccia flanked by a low apron of mass flow deposits, together with (2) an overlying unit ~ 200 m thick composed of Surtseyan volcanic products representing a shoaling (and ultimately emergent) volcanic stage. The succeeding island commenced as a small volcanic shield composed of subaerial ‘a ‘ā lavas whose construction terminated in a caldera collapse that repressurized the magma chamber, presaging a major transition to highly explosive pyroclastic eruptions. They were mainly of sub-Plinian and Plinian type and their recognition on the island provides the first viable explanation for the presence of compositionally similar marine tephras sampled by drilling > 500 km from source, previously considered enigmatic. Eruptions probably took place under ice-poor conditions but evidence for quenching of juvenile clasts suggests that the magmas interacted with water high in the conduit sourced from melting of a small ice cap. The major period of high-discharge sub-Plinian and Plinian eruptions appears to have ended and any future events shall probably comprise small-volume eruptions forming Strombolian scoria cones or glaciovolcanic tuff cones.

Little is known about Antarctic blue whale ( Balaenoptera musculus intermedia ) movement and migration. In many baleen whales, distinct populations arose due to inherited fidelity to migration routes between breeding and feeding areas. To assess whether population structure is present in the form of feeding area fidelity in Antarctic blue whales, we analyzed historical Discovery mark-recovery data with a multistate model to estimate historical interyear movement rates among the 3 ocean basins in the Southern Ocean (Atlantic, Indian, and Pacific) during 1926-1963. We found high probabilities of interyear movement in almost all directions: for blue whales in the Atlantic basin of the Southern Ocean, we estimated that each year 15% (95% interval: 0.66-46%) moved to the Indian and 29% (4-49%) to the Pacific basins; from the Indian basin, 13% (3-33%) moved to the Atlantic and 32% (14-48%) to the Pacific basins; and from the Pacific basin, 28% (13-46%) moved to the Indian and 8% (0.9-24%) to the Atlantic basins. These high estimated movement rates provide little evidence for population structure arising from basin-specific feeding ground fidelity by Antarctic blue whales.

An array of information about the Antarctic ice sheet can be extracted from ice-sheet internal architecture imaged by airborne ice-penetrating radar surveys. We identify, trace and date three key internal reflection horizons (IRHs) across multiple radar surveys from South Pole to Dome A, East Antarctica. Ages of ~38 ± 2.2, ~90 ± 3.6 and ~162 ± 6.7 ka are assigned to the three IRHs, with verification of the upper IRH age from the South Pole ice core. The resultant englacial stratigraphy is used to identify the locations of the oldest ice, specifically in the upper Byrd Glacier catchment and the Gamburtsev Subglacial Mountains. The distinct glaciological conditions of the Gamburtsev Mountains, including slower ice flow, low geothermal heat flux and frozen base, make it the more likely to host the oldest ice. We also observe a distinct drawdown of IRH geometry around South Pole, indicative of melting from enhanced geothermal heat flux or the removal of deeper, older ice under a previous faster ice flow regime. Our traced IRHs underpin the wider objective to develop a continental-scale database of IRHs which will constrain and validate future ice-sheet modelling and the history of the Antarctic ice sheet.

Here, we report the first discovery of Antarctic fossil resin (commonly referred to as amber) within a ~5 cm-thick lignite layer, which constitutes the top part of a ~3 m-long palynomorph-rich and root-bearing carbonaceous mudstone of mid-Cretaceous age. The sedimentary sequence was recovered by the MARUM-MeBo70 seafloor drill rig at Site PS104_20 (73.57° S, 107.09° W; 946 m water depth) from the mid-shelf section of Pine Island trough in the Amundsen Sea Embayment, West Antarctica, during RV Polarstern Expedition PS104 in early 2017. So far, amber deposits have been described from every continent except Antarctica.

Aim Ecologically similar species living in sympatry are expected to segregate to reduce the effects of competition where resources are limiting. Segregation from heterospecifics commonly occurs in space, but it is often unknown whether such segregation has underlying environmental causes. Indeed, species could segregate because of different fundamental environmental requirements (i.e., ‘niche divergence’), because competitive exclusion at sympatric sites can force species to either change the habitat use they would have at allopatric sites (i.e., ‘niche displacement’) or to avoid certain areas, independently of habitat (i.e., ‘spatial avoidance’). Testing these hypotheses requires the comparison between sympatric and allopatric sites. Understanding the competitive mechanisms that underlie patterns of spatial segregation could improve predictions of species responses to environmental change, as competition might exacerbate the effects of environmental change. Location North Atlantic and Arctic. Taxa Common guillemots Uria aalge and Brünnich's guillemots Uria lomvia. Methods Here, we examine support for these explanations for spatial segregation in two closely‐related seabird species, common guillemots ( Uria aalge ) and Brünnich's guillemots ( U. lomvia ). For this, we collated a pan‐Atlantic data set of breeding season foraging tracks from 1046 individuals, collected from 20 colonies (8 sympatric and 12 allopatric). These were analysed with habitat models in a spatially transferable framework to compare habitat preferences between species at sympatric and allopatric sites. Results We found no effect of the distribution of heterospecifics on local habitat preferences of the focal species. We found differences in habitat preferences between species, but these were not sufficient to explain the observed levels of spatial segregation at sympatric sites. Main Conclusions Assuming we did not omit any relevant environmental variables, these results suggest a mix of niche divergence and spatial avoidance produces the observed patterns of spatial segregation.

Microplastic pollution is a growing environmental problem. Consequently, an emerging area of research is the analysis of these micro-particles, to identify the distribution and impacts of plastic in the environment. This paper details the development and application of a pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) method for the quantification of microplastic pollution in terrestrial samples. Initial analysis of plastic standards using Py-GC-MS revealed diagnostic pyrolytic products, which were utilised alongside internal standards and linear regression to create calibrations for each studied synthetic plastic. A microplastic extraction protocol for soils and sediments was developed, namely an overnight density separation with wet peroxide digestion, and its efficacy confirmed through spiking and recovery experiments. Matrix effects were observed for PE, PS and PVC, highlighting the need to use multiple diagnostic compounds per plastic, where possible. Overall, these findings demonstrate that Py-GC-MS can be successfully applied for the determination of microplastic concentrations in terrestrial samples, with a view to establishing effective mitigation strategies.

The Western Antarctic Peninsula (WAP) has been experiencing rapid regional warming since at least the 1950s, however, the impacts of this warming at the local scale are variable and nuanced. Previous studies that have linked sea‐ice variability to biogeochemical cycles and food web dynamics often combine local‐scale biogeochemical data with coarse‐resolution regional satellite sea‐ice data, which may not adequately capture local sea‐ice conditions. In this study, we analyzed local‐scale in situ sea‐ice observations collected as part of a 28‐year record (1992–2020) from the Palmer Long‐Term Ecological Research site at Anvers Island, mid‐WAP, in conjunction with isotopically‐derived sea‐ice meltwater (SIM) fractions and satellite‐derived sea‐ice motion and concentration, to quantify the variability and long‐term trends in local sea‐ice behavior. In situ sea ice observations at Palmer Station displayed higher variability than satellite observations and showed no significant declines over this time, despite region‐wide declines identified in prior studies. Higher spring SIM fractions were attributed to strong northward sea‐ice motion throughout the winter. Applying these local‐scale sea‐ice insights to similarly scaled stratification and chlorophyll‐a measurements, we found that a longer‐lasting, more consistent sea‐ice pack led to greater water column stratification following the spring sea‐ice retreat. Greater sea‐ice persistence and stronger stratification led to larger peaks in chlorophyll‐a, though sea‐ice metrics did not explain the positive temporal trends in either stratification strength or chlorophyll‐a. Through this study, we identify how local sea‐ice observations and meltwater data can enhance satellite data to build an understanding of the intricate connections between ice, water column dynamics, and phytoplankton.

The benthic biodiversity of the abyssal Labrador Sea was investigated using Agassiz trawl and in situ imagery. A megafaunal scaphopod associated with an epizoic anemone was recovered from soft sediments. Morphological and molecular investigations revealed the scaphopod to be an undescribed species in the dentaliid genus Fissidentalium P. Fischer, 1885. The new scaphopod species is characterised by a large size for the genus, is moderately curved, with numerous narrow, longitudinal ribs (60 ribs at 11 mm diameter ventral aperture), a dentaliid radula, and is described herein as Fissidentalium aurae sp. nov. The new species shows a close genetic relationship to congeners of Fissidentalium and separates from the sister genera Dentalium Linnaeus, 1758 and Antalis H. Adams & A. Adams, 1854. Genetic COI barcoding of the epizoic anemone suggests the species is a member of the family Actinostolidae Carlgren, 1932. The discovered association of a burrowing scaphopod with an epifaunal anemone at abyssal depth is a new record for the region and is indicative of how little is known about symbioses in the deep sea.