Search

A new species of nephropid lobster, Hoploparia echinata sp. nov., from the James Ross Island in the Antarctic Peninsula is here described and illustrated. The material was collected in the Santa Marta Formation (Santonian–-Campanian), the basal unit of the Marambio Group, Larsen Basin, located in the western portion of the Antarctic Peninsula. Hoploparia echinata sp. nov. can easily be differentiated from its congeners by the presence of distinct short spines on dorsal and ventral margins on the third maxillipeds, merus of the chelipeds and pereopods; these are the characters not described in other Hoploparia species so far.

In February 2019, during fieldwork at Harmony Point, Nelson Island, South Shetland Islands, Antarctica, a large population of the rare liverwort Hygrolembidium isophyllum (Lepidoziaceae) was discovered. The occurrence of this rare species reinforces the need to preserve Antarctic Specially Protected Area 133.

We developed a high-performance, multichannel, ultra-wideband radar system for measurements of the base and interior of the East Antarctic Ice Sheet. We designed the radar to be of high power (4000-W peak) yet portable and to be able to operate with 60-MHz bandwidth at a center frequency of 200 MHz, providing high sensitivity and fine vertical resolution relative to current technology. We used the radar to perform extensive measurements as a part of a multinational collaboration. We collected data onboard a tracked vehicle outfitted with an array of high-gain antennas. We sounded 2- to 3-km thick ice near Dome Fuji. Preliminary ice thickness data match those obtained via semicoincident measurements performed with a different surface-based pulse modulated radar system operated during the same field campaign, as well as previous airborne measurements. In addition, we mapped internal reflection horizons with fine vertical resolution from 300 m below the ice surface to ∼100 m above the bed. In this article, we provide a detailed overview of the radar instrument design, implementation, and field measurement setup. We present sample data to illustrate its capabilities and discuss how the data collected with it will be valuable for the assessment of promising drilling sites to recover ice cores that are 0.9–1.5 million years old.

In this article, we analyze the impacts of climate change on Antarctic marine ecosystems. Observations demonstrate large-scale changes in the physical variables and circulation of the Southern Ocean driven by warming, stratospheric ozone depletion, and a positive Southern Annular Mode. Alterations in the physical environment are driving change through all levels of Antarctic marine food webs, which differ regionally. The distributions of key species, such as Antarctic krill, are also changing. Differential responses among predators reflect differences in species ecology. The impacts of climate change on Antarctic biodiversity will likely vary for different communities and depend on species range. Coastal communities and those of sub-Antarctic islands, especially range-restricted endemic communities, will likely suffer the greatest negative consequences of climate change. Simultaneously, ecosystem services in the Southern Ocean will likely increase. Such decoupling of ecosystem services and endemic species will require consideration in the management of human activities such as fishing in Antarctic marine ecosystems.

The Retrospective Analysis of Antarctic Tracking Data (RAATD) is a Scientific Committee for Antarctic Research project led jointly by the Expert Groups on Birds and Marine Mammals and Antarctic Biodiversity Informatics, and endorsed by the Commission for the Conservation of Antarctic Marine Living Resources. RAATD consolidated tracking data for multiple species of Antarctic meso- and top-predators to identify Areas of Ecological Significance. These datasets and accompanying syntheses provide a greater understanding of fundamental ecosystem processes in the Southern Ocean, support modelling of predator distributions under future climate scenarios and create inputs that can be incorporated into decision making processes by management authorities. In this data paper, we present the compiled tracking data from research groups that have worked in the Antarctic since the 1990s. The data are publicly available through biodiversity.aq and the Ocean Biogeographic Information System. The archive includes tracking data from over 70 contributors across 12 national Antarctic programs, and includes data from 17 predator species, 4060 individual animals, and over 2.9 million observed locations.

The Filchner-Ronne Ice Shelf, fringing the southern Weddell Sea, is Antarctica's second largest ice shelf. At present, basal melt rates are low due to active dense water formation; however, model projections suggest a drastic increase in the future due to enhanced inflow of open-ocean warm water. Mooring observations from 2014 to 2016 along the eastern flank of the Filchner Trough (76°S) revealed a distinct seasonal cycle with inflow if Warm Deep Water during summer and autumn. Here we present extended time series showing an exceptionally warm and long inflow in 2017, with maximum temperatures exceeding 0.5°C. Warm temperatures persisted throughout winter, associated with a fresh anomaly, which lead to a change in stratification over the shelf, favoring an earlier inflow in the following summer. We suggest that the fresh anomaly developed upstream after anomalous summer sea ice melting and contributed to a shoaling of the shelf break thermocline.

The Southern Ocean is chronically undersampled due to its remoteness, harsh environment, and sea ice cover. Ocean circulation models yield significant insight into key processes and to some extent obviate the dearth of data; however, they often underestimate surface mixed layer depth (MLD), with consequences for surface water-column temperature, salinity, and nutrient concentration. In this study, a coupled circulation and sea ice model was implemented for the region adjacent to the West Antarctic Peninsula, a climatically sensitive region which has exhibited decadal trends towards higher ocean temperature, shorter sea ice season, and increasing glacial freshwater input, overlain by strong interannual variability. Hindcast simulations were conducted with different air-ice drag coefficients and Langmuir circulation parameterizations to determine the impact of these factors on MLD. Including Langmuir circulation deepened the surface mixed layer, with the deepening being more pronounced in the shelf and slope regions. Optimal selection of an air-ice drag coefficient also increased modeled MLD by similar amounts and had a larger impact in improving the reliability of the simulated MLD interannual variability. This study highlights the importance of sea ice volume and redistribution to correctly reproduce the physics of the underlying ocean, and the potential of appropriately parameterizing Langmuir circulation to help correct for biases towards shallow MLD in the Southern Ocean. The model also reproduces observed freshwater patterns in the West Antarctic Peninsula during late summer and suggests that areas of intense summertime sea ice melt can still show net annual freezing due to high sea ice formation during the winter.

Understanding climate proxy records that preserve physical characteristics of past climate is a prerequisite to reconstruct long-term climatic conditions. Water stable isotope ratios (δ18O) constitute a widely used proxy in ice cores to reconstruct temperature and climate. However, the original climate signal is altered between the formation of precipitation and the ice, especially in low-accumulation areas such as the East Antarctic Plateau. Atmospheric conditions under which the isotopic signal is acquired at Aurora Basin North (ABN), East Antarctica, are characterized with the regional atmospheric model Modèle Atmosphérique Régional (MAR). The model shows that 50% of the snow is accumulated in less than 24 days year−1. Snowfall occurs throughout the year and intensifies during winter, with 64% of total accumulation between April and September, leading to a cold bias of −0.86°C in temperatures above inversion compared to the annual mean of −29.7°C. Large snowfall events are associated with high-pressure systems forcing warm oceanic air masses toward the Antarctic interior, which causes a warm bias of +2.83°C. The temperature-δ18O relationship, assessed with the global atmospheric model ECHAM5-wiso, is primarily constrained by the winter variability, but the observed slope is valid year-round. Three snow δ18O records covering 2004–2014 indicate that the anomalies recorded in the ice core are attributable to the occurrence of warm winter storms bringing precipitation to ABN and support the interpretation of δ18O in this region as a marker of temperature changes related to large-scale atmospheric conditions, particularly blocking events and variations in the Southern Annular Mode.

I denne oppgaven er forekomsten av fasescintillasjoner på GNSS-signaler over deler av Dronning Maud Land i Antarktis kartlagt, ved bruk av scintillasjonsmottakere på Troll stasjonen (geografiske koordinater: 72.0◦S, 2.5◦Ø, magnetiske koordinater: 62.8◦S, 47.8◦Ø) og SANAE IV (geografiske koordinater: 71.7◦S, 2.8◦V, magnetiske koordinater: 62.0◦S, 45.0◦Ø). Ionosfæren i dette området er lite studert tidligere, og dette er de første resultatene som presenteres fra det nylig etablerte Troll ionosfæriske observatoriet. Den første delen av oppgaven er en statistisk studie hvor forekomsten av scintillasjoner i 2018 er kartlagt. Hovedfunnet i denne studien er at høye fasescintillasjoner kun forekommer ved høy geomagnetisk aktivitet, forekomsten av scintillasjoner er høyere postmidnatt enn premidnatt og at scintillasjoner forekommer både innenfor og nord for den statistiske auroraovalen. I denne oppgaven er det også gjennomført to kasusstudier, en fra februar 2018 og en fra mars 2018. Kasusstudiene brukte satellittdata fra solvinden, Swarm, DMSP og bakkebaserte instrumenter: scintillasjonsmottakere, magnetometere og Superdarn, fra både den nordlige og sørlige halvkule. Hovedfunnene fra kasusstudiene er at scintillasjoner på Troll og Sanae kan assosieres med partikkelnedbør, sterke vestgående strømmer og høye konveksjonshastigheter. De viste også en hvis symmetri i forekomsten av scintillasjoner, men scintillasjonene var kraftigere og var til stede over en lengre tidsperiode i Antarktis enn på Færøyene.

The shape of ice shelf cavities are a major source of uncertainty in understanding ice-ocean interactions. This limits assessments of the response of the Antarctic ice sheets to climate change. Here we use vibroseis seismic reflection surveys to map the bathymetry beneath the Ekström Ice Shelf, Dronning Maud Land. The new bathymetry reveals an inland-sloping trough, reaching depths of 1,100 m below sea level, near the current grounding line, which we attribute to erosion by palaeo-ice streams. The trough does not cross-cut the outer parts of the continental shelf. Conductivity-temperature-depth profiles within the ice shelf cavity reveal the presence of cold water at shallower depths and tidal mixing at the ice shelf margins. It is unknown if warm water can access the trough. The new bathymetry is thought to be representative of many ice shelves in Dronning Maud Land, which together regulate the ice loss from a substantial area of East Antarctica.

Antarktis kan virke som det sover under en beskyttende dyne av snø og is. Kontinentet har vært lite påvirket av menneskelig aktivitet, men har nå begynt å våkne. Klimaendringene har nådd fram til det frosne kontinentet ved Sørpolen. Relativt varme og salte havstrømmer kommer seg nå helt inn til isen. Men satellitter viser at det smelter mindre is enn det som hadde vært mulig med den tilgjengelige mengden varme. Vi har brukt observasjoner og resultater fra laboratoriet for å forklare hvor det varme vannet blir av.

Combining information from several channels of the Norwegian Institute for Air Research (NILU-UV) irradiance meter, one may determine the total ozone column (TOC) amount. A NILU-UV instrument has been deployed and operated on two locations at Troll research station in Jutulsessen, Queen Maud Land, Antarctica, for several years. The method used to determine the TOC amount is presented, and the derived TOC values are compared with those obtained from the Ozone Monitoring Instrument (OMI) located on NASA’s AURA satellite. The findings show that the NILU-UV TOC amounts correlate well with the results of the OMI and that the NILU-UV instruments are suitable for monitoring the long-term change and development of the ozone hole. Because of the large footprint of OMI, NILU-UV is a more suitable instrument for local measurements.

Abstract Individual heterogeneity in diet and foraging behaviour is common in wild animal populations, and can be a strong determinant of how populations respond to environmental changes. Within populations, variation in foraging behaviour and the occurrence of individual tactics in relation to resources distribution can help explain differences in individual fitness, and ultimately identify important factors affecting population dynamics. We examined how foraging behaviour and habitat during the breeding period related to the physiological state of a long-ranging seabird adapted to sea ice, the Antarctic petrel Thalassoica antarctica. Firstly, using GPS tracking and state-switching movement modelling (hidden Markov models) on 124 individual birds, we tested for the occurrence of distinct foraging tactics within our study population. Our results highlight a large variation in the movement and foraging behaviour of a very mobile seabird, and delineate distinct foraging tactics along a gradient from foraging in dense pack ice to foraging in open water. Secondly, we investigated the effects of these foraging tactics on individual state at return from a foraging trip. We combined movement data with morphometric and physiological measurements of a suite of plasma metabolites that provided a general picture of a bird's individual state. Foraging in denser sea ice was associated with lower gain in body mass during brooding, as well as lower level of energy acquisition (plasma triacylglycerol) during both brooding and incubation. We found no clear relationship between the foraging tactic in relation to sea ice and the energetic stress (changes in plasma corticosterone), energetic balance (β-hydroxybutyrate) or trophic level (δ15N). However, a shorter foraging range was related to both the energetic balance (positively) and the trophic level (negatively). Our results highlight a diverse range of foraging tactics in relation to sea ice in Antarctic petrels. While the various foraging tactics do not seem to strongly alter energetic balance, they may affect other aspects of Antarctic petrels' physiology. Future changes in sea-ice habitats can thus be expected to have an impact on the individual state of seabirds such as Antarctic petrels, which could ultimately affect their population dynamics. Nonetheless, strong individual heterogeneity in the use of sea-ice habitats by a typical pagophilic species might strengthen its resilience to environmental changes and in particular to forecasted sea-ice loss. A free Plain Language Summary can be found within the Supporting Information of this article.

Microcontinents and continental fragments are small pieces of continental crust that are surrounded by oceanic lithosphere. Although classically associated with passive margin formation, here we present several preserved microcontinents and continental fragments associated with subduction systems. They are located in the Coral Sea, South China Sea, central Mediterranean and Scotia Sea regions, and a “proto-microcontinent,” in the Gulf of California. Reviewing the tectonic history of each region and interpreting a variety of geophysical data allows us to identify parameters controlling the formation of microcontinents and continental fragments in subduction settings. All these tectonic blocks experienced long, complex tectonic histories with an important role for developing inherited structures. They tend to form in back-arc locations and separate from their parent continent by oblique or rotational kinematics. The separated continental pieces and associated marginal basins are generally small and their formation is quick (<50 Myr). Microcontinents and continental fragments formed close to large continental masses tend to form faster than those created in systems bordered by large oceanic plates. A common triggering mechanism for their formation is difficult to identify, but seems to be linked with rapid changes of complex subduction dynamics. The young ages of all contemporary pieces found in situ suggest that microcontinents and continental fragments in these settings are short lived. Although presently the amount of in-situ subduction-related microcontinents is meager (an area of 0.56% and 0.28% of global, non-cratonic, continental crustal area and crustal volume, respectively), through time microcontinents contributed to terrane amalgamation and larger continent formation.

Winter to summer CO2 dynamics within landfast sea ice in McMurdo Sound (Antarctica) were investigated using bulk ice pCO2 measurements, air-snow-ice CO2 fluxes, dissolved inorganic carbon (DIC), total alkalinity (TA), and ikaite saturation state. Our results suggest depth-dependent biotic and abiotic controls that led us to discriminate the ice column in three layers. At the surface, winter pCO2 supersaturation drove CO2 release to the atmosphere while spring-summer pCO2 undersaturation led to CO2 uptake most of the time. CO2 fluxes showed a diel pattern superimposed upon this seasonal pattern which was potentially assigned to either ice skin freeze-thaw cycles or diel changes in net community production. In the ice interior, the pCO2 decrease across the season was driven by physical processes, mainly independent of the autotrophic and heterotrophic phases. Bottom sea ice was characterized by a massive biomass build-up counterintuitively associated with transient heterotrophic activity and nitrate plus nitrite accumulation. This inconsistency is likely related to the formation of a biofilm. This biofilm hosts both autotrophic and heterotrophic activities at the bottom of the ice during spring and may promote calcium carbonate precipitation.

Mass loss from the Antarctic Ice Sheet to the ocean has increased in recent decades, largely because the thinning of its floating ice shelves has allowed the outflow of grounded ice to accelerate. Enhanced basal melting of the ice shelves is thought to be the ultimate driver of change, motivating a recent focus on the processes that control ocean heat transport onto and across the seabed of the Antarctic continental shelf towards the ice. However, the shoreward heat flux typically far exceeds that required to match observed melt rates, suggesting that other critical controls exist. Here we show that the depth-independent (barotropic) component of the heat flow towards an ice shelf is blocked by the marked step shape of the ice front, and that only the depth-varying (baroclinic) component, which is typically much smaller, can enter the sub-ice cavity. Our results arise from direct observations of the Getz Ice Shelf system and laboratory experiments on a rotating platform. A similar blocking of the barotropic component may occur in other areas with comparable ice–bathymetry configurations, which may explain why changes in the density structure of the water column have been found to be a better indicator of basal melt rate variability than the heat transported onto the continental shelf. Representing the step topography of the ice front accurately in models is thus important for simulating ocean heat fluxes and induced melt rates.

Dronning Maud Land (DML) is a key area for the better understanding of the geotectonic history and amalgamation processes of the southern part of Gondwana. Here, we present comprehensive new zircon U–Pb–Hf–O, whole-rock Sm–Nd isotopic and geochemical data for late Neoproterozoic-Cambrian igneous rocks along a profile from central to eastern DML, which provides new insights into the crustal evolution and tectonics of the region. In central DML, magmatism dominantly occurred at 530–485 Ma, with 650–600 Ma charnockite and anorthosite locally distributed at its eastern periphery. In contrast, eastern DML experienced long-term and continuous granitic magmatism from ca. 650 Ma to 500 Ma. In central DML, the 650–600 Ma samples are characterized by highly elevated δ18O (7.5–9.5‰) associated with slightly negative to positive εHf(t) values (−1 to +3), indicating significant addition of high-δ18O crustal components, such as sedimentary material at the margin of the Kalahari Craton. Evolved Hf isotopic signatures (εHf(t) = −15 to −6) and moderately elevated O isotopic data (δ18O = 6–8‰) of the Cambrian granitic rocks from central DML indicate a significant incorporation of the pre-existing, old continental crust. In eastern DML, the suprachondritic Hf–Nd isotope signatures and moderate δ18O values of the late Neoproterozoic granites (650–550 Ma) from the Sør Rondane Mountains support the view that they mainly originated from crust of the Tonian Oceanic Arc Super Terrane (TOAST). The post-540 Ma granites, however, have more evolved Hf and Nd isotopic compositions, suggesting an increasing involvement of older continental components during Cambrian magmatism. Nd isotopes of the Cambrian granitic rocks in DML display an increasingly more radiogenic composition towards the east with model ages ranging from late Archean to Mesoproterozoic times, which is in line with the isotopic trend of the Precambrian basement in this region. The late Neoproterozoic (>600 Ma) igneous rocks in central and eastern DML were emplaced in two independent subduction systems, at the periphery of the eastern Kalahari Craton and somewhere within the Mozambique Ocean respectively. The accretion and assembly of the TOAST to the eastern margin of the Kalahari Craton and their collision with surrounding continental blocks was followed by extensive post-collisional magmatism due to delamination tectonics and orogenic collapse in the Cambrian. The late Neoproterozoic–Cambrian igneous rocks in DML thus record an orogenic cycle from subduction-accretion, continental collision to post-collisional process during and after the assembly of Gondwana.