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The paper studies the ice cover of the Trooz Glacier, Kyiv Peninsula, West Antarctic Peninsula. The main goal of the work is to study the velocity dynamics of various parts of the Trooz Glacier in 2016-2022 based on remote sensing data and to compare them with changes in meteorological variables. The glacier's velocity was determined using 7-year data from the Copernicus Sentinel-1 satellite system based on the offset tracking technique. The characteristics of climatic changes during the same time intervals were determined according to the POWER project from NASA. To analyze the velocity field of the Trooz Glacier over time, 100 control points were selected along the entire valley from the mouth to the upland of the tributaries. For these points, values of the glacier velocity were calculated every 12 days for seven years, from 23.11.2015 to 28.12.2022. The entire glacier valley was divided into subclusters with their own average surface velocities and accelerations. To determine the level of climate change's influence on the velocities of different parts of the Trooz Glacier, we used the method of cross-correlation. The ice flow reacted to climatic changes with a certain delay. Annual velocity fluctuations of various parts and a slight glacier movement acceleration from 2015 to 2022 were identified. The latter amounted to 7-9% of the 2016-year speed. At the same time, only in the terminus area during the studied period was there a slight slowdown in the average annual velocity detected from 2.25 m day-1 in 2016 to 2.1 m day-1 in 2022. The most intensive climatic parameters affect the middle and lower parts of the Trooz Glacier. Among the main parameters, the near-surface environment temperature can be seen as the most influential force. Temperature changes impact the glacier velocity within the first 12 to 36 days; the effect can appear later with lag intervals of up to 120 days. The role of environmental temperature is significant for the middle part of the glacier, where its valley becomes wide. For the lower part and terminus region of the glacier, the temperature effect is most significant, with the reaction of the ice flow to temperature changes occurring in the coming days. Shortwave solar radiation and ultraviolet index were also established as influencers, but only for the lower and middle glacier parts, with a lag from 12 to 48 days. The influence of the precipitation amount was the most detectable only in the lower part of the glacier. [ABSTRACT FROM AUTHOR]

Background: This dataset relates to the biodiversity census carried out during the Belgica 121 (B121) expedition to the Western Antarctic Peninsula from February to March 2019. One of the aims of the campaign was to explore the surroundings of the Gerlache Strait and to carry out a detailed biodiversity census focusing on inter- and subtidal shallow-water areas using both classic descriptive marine ecology methods, as well as state-of-the art techniques (habitat mapping, genetics, trophic ecology). The biodiversity census was carried out onboard a nimble research vessel, RV Australis. This dataset will offer access to the raw data on biodiversity occurrences, obtained using a range of methods described in this data paper. New information: New raw biodiversity data for a poorly-sampled region (Western Antarctic Peninsula) with a special focus on shallow ecosystems. [ABSTRACT FROM AUTHOR]

The upward evolution of temperatures in the Antarctic Peninsula has weakened and even reversed in the last two decades. Due to the long-term variability in the region it is not easy to assess whether recent cooling trends are consistent with the internal variability or not. For this reason, this paper assesses the robustness of the trends by analysing their sensitivity with respect to the period selected. Every possible temperature trend in the interval 1958–2016 has been calculated and displayed in a two-dimensional parameter diagram. The results suggest that the warming observed in the Antarctic Peninsula since 1958 is quite robust, as all periods longer than 30 years exhibit statistically significant changes, especially in summer (with lower magnitude and higher significance) and autumn and winter (with larger magnitude and lower significance). Periods shorter than 30 years exhibit alternations of warming and cooling periods, and therefore do not represent robust trends even if they are statistically significant. Consequently, the recent 20-year cooling trend cannot be considered at the moment as evidence of a shift in the overall sign of the trend. [ABSTRACT FROM AUTHOR]

Although the relationship between surface air temperature and glacial discharge has been studied in the Northern Hemisphere for at least a century, similar studies for Antarctica remain scarce and only for the past four decades. This data scarcity is due to the extreme meteorological conditions and terrain inaccessibility. As a result, the contribution of glacial discharge in Antarctica to global sea-level rise is still attached with great uncertainties, especially from partly glaciated hydrological basins as can be found in the Antarctic Peninsula. In this paper, we propose a simplified model based on the Monte Carlo method and Fourier analysis for estimating discharge in partly glaciated and periglacial hydrological catchments with a summer melt period. Our model offers the advantage of scarce data requirements and quick recognition of periglacial environments. Discharge was found to be highly correlated with surface air temperature for the partially glaciated hydrological catchments on Potter Peninsula, King George Island (Isla 25 Mayo). The model is simple to implement and requires few variables to make most versatile simulations. We have obtained a monthly simulated maximum flow estimates between 0.74 and 1.07m³ s-1 for two creeks (South and North Potter) with a very good fit to field observations. The glacial mean monthly discharge during summer months was estimated to 0.44 ± 0.02m³ s-1 for South Potter Creek and 0.55 ± 0.02m³³ s-1 for North Potter Creek. This article is part of the theme issue 'The marine system of the West Antarctic Peninsula: status and strategy for progress in a region of rapid change'. [ABSTRACT FROM AUTHOR]

The Antarctic Peninsula is under pressure from non-native plants and this risk is expected to increase under climate warming. Establishment and subsequent range expansion of non-native plants depend in part on germination ability under Antarctic conditions, but quantifying these processes has yet to receive detailed study. Viability testing and plant growth responses under simulated Antarctic soil surface conditions over an annual cycle show that 16 non-native species, including grasses, herbs, rushes and a succulent, germinated and continued development under a warming scenario. Thermal germination requirement (degree day sum) was calculated for each species and field soil-temperature recordings indicate that this is satisfied as far south as 72° S. Here, we show that the establishment potential of non-native species, in number and geographical range, is considerably greater than currently suggested by species distribution modelling approaches, with important implications for risk assessments of non-native species along the Antarctic Peninsula. Stef Bokhorst et al. simulate a warming scenario in Antarctic soil under laboratory conditions and report the germination and growth of sixteen non-native plant species. These experimental results, combined with calculations of thermal germination requirement at +3 °C and +5 °C warming scenarios demonstrate that the risk of establishment by non-native species in Antarctica may be greater than previously suggested by species distribution modelling approaches. [ABSTRACT FROM AUTHOR]

Parts of Antarctica were amongst the most rapidly changing regions of the planet during the second half of the Twentieth Century. Even so, today, most of Antarctica remains in the grip of continental ice sheets, with only about 0.2% of its overall area being ice-free. The continent's terrestrial fauna consists only of invertebrates, with just two native species of insects, the chironomid midges Parochlus steinenii and Belgica antarctica. We integrate ecophysiological information with the development of new high-resolution climatic layers for Antarctica, to better understand how the distribution of P. steinenii may respond to change over the next century under different IPCC climate change scenarios. We conclude that the species has the potential to expand its distribution to include parts of the west and east coasts of the Antarctic Peninsula and even coastal ice-free areas in parts of continental Antarctica. We propose P. steinenii as an effective native sentinel and indicator species of climate change in the Antarctic. [ABSTRACT FROM AUTHOR]

Climate‐induced range overlap can result in novel interactions between similar species and potentially lead to competitive exclusion. The West Antarctic Peninsula (WAP) is one of the most rapidly warming regions on Earth and is experiencing a poleward climate migration from a polar to subpolar environment. This has resulted in a range expansion of the ice‐intolerant gentoo penguins (Pygoscelis papua) and a coincident decrease in ice‐obligate Adélie penguins (P. adeliae) near Palmer Station, Anvers Island, WAP. Ecologically similar species that share a limited prey resource must occupy disparate foraging niches in order to co‐exist. Therefore, we determined the extent of foraging and dietary niche segregation between Adélie and gentoo penguins during the austral breeding season near Palmer Station. This research was conducted across six breeding seasons, from 2009 to 2014, which allowed us to investigate niche overlap in the context of interannual resource variability. Using biotelemetry and diet sampling, we found substantial overlap in the diets of Adélie and gentoo penguins, who primarily consumed Antarctic krill (Euphausia superba); however, our results showed that Adélie and gentoo penguins partitioned this shared prey resource through horizontal segregation of their core foraging areas. We did not find evidence that Antarctic krill were a limiting resource during the breeding season or that climate‐induced sympatry of Adélie and gentoo penguins resulted in competition for prey or caused the subsequent differing population trajectories. This apparent absence of resource competition between Adélie and gentoo penguins throughout this study implies that current population trends in this region are governed by other biological and physical factors. Our results highlight the importance of understanding the mechanistic processes that influence top predator populations in the context of climate‐driven ecosystem shifts. In this study, we investigated foraging and dietary niche partitioning between two recently sympatric Pygoscelis penguin populations on the West Antarctic Peninsula. We did not find evidence that climate‐induced sympatry in this scenario resulted in competitive exclusion. The results of this study provide important and timely insight into the underlying mechanistic processes driving penguin population changes in the Southern Ocean. [ABSTRACT FROM AUTHOR]

Almost three decades of bottom pressure recorder (BPR) measurements at the Drake Passage, and 31 years of hourly tide gauge data from the Vernadsky Research Base on the Antarctic Peninsula, have been used to investigate the temporal and spatial variations in this region of the three main long-period tides Mf, Mm and Mt (in order of decreasing amplitude, with periods of a fortnight, a month and one-third of a month, respectively). The amplitudes of Mf and Mt, and the phase lags for all three constituents, vary over the nodal cycle (18.61 years) in essentially the same way as in the equilibrium tide, so confirming the validity of Doodson's "nodal factors" for these constituents. The amplitude of Mm is found to be essentially constant, and so inconsistent at the 3δ level from the ±13% (or ~ ±0:15 mbar) anticipated variation over the nodal cycle, which can probably be explained by energetic non-tidal variability in the records at monthly timescales and longer. The north-south differences in amplitude for all three constituents are consistent with those in a modern ocean tide model (FES2014), as are those in phase lag for Mf and Mt, while the phase difference for Mm is smaller than in the model. BPR measurements are shown to be considerably superior to coastal tide gauge data in such studies, due to the larger proportion of non-tidal variability in the latter. However, correction of the tide gauge records for non-tidal variability results in the uncertainties in nodal parameters being reduced by a factor of 2 (for Mf at least) to a magnitude comparable (approximately twice) to those obtained from the BPR data. [ABSTRACT FROM AUTHOR]

Abstract: The western Antarctic Peninsula (WAP) is a bellwether of global climate change and natural laboratory for identifying interactions between climate and ecosystems. The Palmer Long‐Term Ecological Research (LTER) project has collected data on key ecological and environmental processes along the WAP since 1993. To better understand how key ecological parameters are changing across space and time, we developed a novel seascape classification approach based on in situ temperature, salinity, chlorophyll a, nitrate + nitrite, phosphate, and silicate. We anticipate that this approach will be broadly applicable to other geographical areas. Through the application of self‐organizing maps (SOMs), we identified eight recurrent seascape units (SUs) in these data. These SUs have strong fidelity to known regional water masses but with an additional layer of biogeochemical detail, allowing us to identify multiple distinct nutrient profiles in several water masses. To identify the temporal and spatial distribution of these SUs, we mapped them across the Palmer LTER sampling grid via objective mapping of the original parameters. Analysis of the abundance and distribution of SUs since 1993 suggests two year types characterized by the partitioning of chlorophyll a into SUs with different spatial characteristics. By developing generalized linear models for correlated, time‐lagged external drivers, we conclude that early spring sea ice conditions exert a strong influence on the distribution of chlorophyll a and nutrients along the WAP, but not necessarily the total chlorophyll a inventory. Because the distribution and density of phytoplankton biomass can have an impact on biomass transfer to the upper trophic levels, these results highlight anticipated links between the WAP marine ecosystem and climate. [ABSTRACT FROM AUTHOR]

Southern Hemisphere humpback whales breed in tropical waters and migrate to Antarctica to forage. While the breeding grounds are well defined, the population structure on Antarctic feeding grounds is poorly described. The Western Antarctic Peninsula (WAP) is of particular interest, where rapidly changing environmental conditions could alter prey distribution or migration pathways. To examine changes in the population of whales around the WAP, we used mitochondrial DNA (mtDNA) and 15 microsatellite loci. We compared our WAP dataset to a dataset collected 18 years earlier, and identified new haplotypes for the region, but found no significant difference between the datasets. We compared whales from the WAP to breeding populations in Oceania, Colombia, and Brazil. We used an Analysis of Molecular Variance to confirm significant genetic differentiation between the WAP and each breeding ground (overall FST = 0.035/0.007 mtDNA/microsatellite, p < 0.001) except Colombia. Bayesian mixed-stock analyses showed a large apportionment to Colombia (mtDNA 93.0%; CL 91–99%; microsatellites 86%; CL 72–93%) and a small apportionment to French Polynesia/Samoan Islands (mtDNA 2.9%; CL 0.0–11.5%; microsatellites 8.9%; CL 0–22%), supporting the strong connection between Colombia and the WAP. Assignment tests allocated 81 individuals to Colombia and two to French Polynesia/Samoan Islands. No other breeding grounds had significant apportionments. Direct connectivity of French Polynesia to the WAP was confirmed with the first genotype match of French Polynesia to a feeding area. Continued genetic monitoring will highlight the complex patterns of humpbacks in this rapidly changing climate. Our results serve as a baseline for humpback whale population structure, illustrate mixed-stock analysis as a useful tool for migrating wildlife, and aid in future management considerations for humpbacks. [ABSTRACT FROM AUTHOR]

The present study characterizes the spatial distribution of seaweed diversity on eight islands from the South Shetlands based on an updated taxonomic survey, discussing the higher number of species compared with previous studies and the possible relationships with environmental parameters. Seaweeds were sampled in Deception, Livingston, Halfmoon, Robert, Nelson, King George, Penguin, and Elephant Islands during the austral summer between 2010 and 2013 in intertidal and shallow subtidal zones. The taxonomic analyses evaluated morphological characteristics, reproductive structures, and molecular features. Physicochemical parameters of seawater were also monitored using standard analytical methods. A total of 104 species of benthic marine algae were identified (28 Phaeophyceae, 24 Chlorophyta, and 52 Rhodophyta), ~82% of all seaweeds taxa described to Antarctica, including six new records previously recorded only at lower latitudes, four confirmed taxa, and two putative new species. Spatial variation in species diversity was observed among the collecting sites, and Livingston and King George Islands showed the highest diversity among the islands. Deception, an area with geothermal activity and intense tourism, was dominated by opportunistic and broadly distributed filamentous green algae. Antarctic macroalgae diversity was higher than in previous studies, most likely due to more efficient techniques of sampling, and combined taxonomical methods. However, changes in the biogeographical distribution or introduction of some taxa, resulting from anthropogenic activities and/or climate changes, should be considered. Therefore, the higher number of taxa and the new records reported in this study suggest the need for long-term monitoring in the area for conservation purposes. [ABSTRACT FROM AUTHOR]

Sponge communities on the Antarctic continental shelf currently represent one of the most extensive sponge grounds in the world, and all sponge classes are known to occur in the Southern Ocean. Main objectives of this study conducted at the tip of the Antarctic Peninsula were (1) to identify all sampled sponges and (2) to investigate whether the species composition and species richness of Southern Ocean sponge communities in the area of the Antarctic Peninsula are significantly influenced by environmental variables. The studied material originated from 25 AGT catches and was sampled during the expedition ANT-XXIX/3 of RV Polarstern. Samples were collected in three large-scale areas in the vicinity of the Antarctic Peninsula: Bransfield Strait, Drake Passage and Weddell Sea. The following six environmental variables were measured from bottom water samples (except for sea-ice cover): depth (m), light transmission (%), oxygen (µmol/kg), salinity, sea-ice cover (%) and temperature (°C). Two hundred and sixty-three sponge samples were analyzed, and 81 species of 33 genera from all Porifera classes (Calcarea, Demospongiae, Hexactinellida and Homoscleromorpha) were identified. Total numbers of sponge species per sample station ranged from 1 to 29. A detrended correspondence analysis and a backward-stepwise model selection were performed to check whether species composition and richness were significantly influenced by environmental variables. The analyses revealed that none of the measured environmental variables significantly influenced species composition but that species richness was significantly influenced by (1) temperature and (2) the combination of temperature and depth. Results of this study are of crucial importance for development, performance and assessment of future protection strategies in case of ongoing climatic changes at the Antarctic Peninsula. [ABSTRACT FROM AUTHOR]

Benthic ecological surveys using standardized methods are crucial for assessing changes associated with several threats in the Southern Ocean. The acquisition of data on assemblage structure over a variety of spatial scales is important to understand the variation of biodiversity patterns. During the ANT XXIX/3 (PS81) expedition of RV Polarstern, three different regions at the tip of the Antarctic Peninsula were sampled: the northwestern Weddell Sea, the Bransfield Strait, and the northern boundary of the South Shetland Archipelago in the Drake Passage. The aim of this study was to characterize the distribution and biodiversity patterns of ophiuroid assemblages in these regions and depths. We quantified different community parameters in terms of the number of species, abundance, and biomass. Additionally, we calculated various components of species diversity (alpha, beta, and gamma diversity) over the three regions. Based on the benthic surveys, we collected 3331 individuals that were identified to species level (17 species). Overall, species diversity, as measured based on rarefaction, species richness and evenness estimators, was higher in the Bransfield Strait compared to the Weddell Sea and Drake Passage. Two deep stations in the Weddell Sea showed high dominance only of Ophionotus victoriae. Significant differences in the patterns of alpha diversity were found among the regions but not between depth zones, whereas beta diversity showed no differences. Regarding the resemblance among the ophiuroid assemblages of each region, there was a significant gradient from east to west with a maximum distance between the stations in the Drake Passage and the Weddell Sea. This study provides a baseline for detecting potential effects related to climate change, and it furnishes a basis for the implementation of monitoring schemes of Antarctic assemblages. [ABSTRACT FROM AUTHOR]

The Antarctic Peninsula is one of the areas where the climate is changing at the fastest pace, having several effects on the populations of pygoscelid penguins. Few studies have analysed the variation in immune parameters of antarctic birds in a geographical context; thus, analyses of geographical differences in the immune components of wild pygoscelid penguins are still scarce. Leukocyte counts in birds provide information on their immunity and physiological stress. The objective of this study was to analyse the leukocyte counts in penguins of the genus Pygoscelis (gentoo, Adélie and chinstrap penguins), covering sites along the South Shetland Islands and some islands on the west coast of the Antarctic Peninsula. Our results revealed differences in the number of heterophils and eosinophils and in the heterophil/lymphocyte ratio in the northeastern populations of gentoo and Adélie penguins as compared to the rest of the colonies studied. The results contribute to better understanding of the variations in physiological parameters of penguins related to a geographical context. [ABSTRACT FROM AUTHOR]

At a global scale, there is no evidence for synchronous multi-decadal warm (‘Medieval Warm Period’, MWP) or cold (‘Little Ice Age’, LIA) periods in the late Holocene. On the other hand, there is good correspondence globally in the timing of MWP or LIA and phases of glacier retreat and advance, respectively, with local exceptions mainly explained by the precipitation regime. Antarctica exhibits contrasting patterns, both regarding the existence of these two historical climatic periods and the glacial responses to climatic forcing. Here, we present evidence for glacial retreat corresponding to the MWP and a subsequent LIA advance at Rothera Point (67°34′S; 68°07′W) in Marguerite Bay, western Antarctic Peninsula. Deglaciation started at ca. 961–800 cal. yr BP or before, reaching a position similar to or even more withdrawn than the current state, with the subsequent period of glacial advance commencing between 671 and 558 cal. yr BP and continuing at least until 490–317 cal. yr BP. Based on new radiocarbon dates, during the MWP, the rate of glacier retreat was 1.6 m yr−1, which is comparable with recently observed rates (~0.6 m yr−1 between 1993 and 2011 and 1.4 m yr−1 between 2005 and 2011). Moreover, despite the recent air warming rate being higher, the glacial retreat rate during the MWP was similar to the present, suggesting that increased snow accumulation in recent decades may have counterbalanced the higher warming rate. [ABSTRACT FROM AUTHOR]

Intense regional warming was observed in the western Antarctic Peninsula ( WAP) over the last 50 years. Here, we investigate the impact of climate change on primary production ( PP) in this highly productive region. This study is based on temporal data series of ozone thickness (1972-2010), sea ice concentration (1978-2010), sea-surface temperature (1990-2010), incident irradiance (1988-2010) and satellite-derived chlorophyll a concentration (Chl-a, 1997-2010) for the coastal WAP. In addition, we apply a photosynthesis/photoinhibition spectral model to satellite-derived data (1997-2010) to compute PP and examine the separate impacts of environmental forcings. Since 1978, sea ice retreat has been occurring earlier in the season (in March in 1978 and in late October during the 2000s) while the ozone hole is present in early spring (i.e. August to November) since the early 1990s, increasing the intensity of ultraviolet-B radiation ( UVBR, 280-320 nm). The WAP waters have also warmed over 1990-2010. The modelled PP rates are in the lower range of previously reported PP rates in the WAP. The annual open water PP in the study area increased from 1997 to 2010 (from 0.73 to 1.03 Tg C yr−1) concomitantly with the increase in the production season length. The coincidence between the earlier sea ice retreat and the presence of the ozone hole increased the exposure to incoming radiation ( UVBR, UVAR and PAR) and, thus, increased photoinhibition during austral spring (September to November) in the study area (from 0.014 to 0.025 Tg C yr−1). This increase in photoinhibition was minor compared to the overall increase in PP, however. Climate change hence had an overall positive impact on PP in the WAP waters. [ABSTRACT FROM AUTHOR]

Sinking of dense water from Antarctic coastal polynyas produces Antarctic Bottom Water (AABW), which is the densest water in the global overturning circulation and is a key player in climate change as a significant sink for heat and carbon dioxide. Very recent studies have suggested that landfast sea ice (fast ice) plays an important role in the formation and variability of the polynyas and possibly AABW. However, they have been limited to regional and case investigations only. This study provides the first coincident circumpolar mapping of Antarctic coastal polynyas and fast ice. The map reveals that most of the polynyas are formed on the western side of fast ice, indicating an important role of fast ice in the polynya formation. Winds diverging from a boundary comprising both coastline and fast ice are the primary determinant of polynya formation. The blocking effect of fast ice on westward sea ice advection by the coastal current would be another key factor. These effects on the variability in sea ice production for 13 major polynyas are evaluated quantitatively. Furthermore, it is demonstrated that a drastic change in fast ice extent, which is particularly vulnerable to climate change, causes dramatic changes in the polynyas and possibly AABW formation that can potentially contribute to further climate change. These results suggest that fast ice and precise polynya processes should be addressed by next-generation models to produce more accurate climate projections. This study provides the boundary and validation data of fast ice and sea ice production for such models. [ABSTRACT FROM AUTHOR]

The effects of climate change along the climatically sensitive Western Antarctic Peninsula (WAP) on active layer dynamics have just begun to be monitored. But extreme climates and difficult access make borehole installation here challenging. This study was designed to examine the ability of two commonly used, minimally intrusive techniques (the Stefan and Kudryavtsev equations) to predict active layer temperature dynamics and maximum active layer thickness (ALT) on Amsler Island, on the WAP. The ALT in soils and unconsolidated materials was predicted to be between 4.7 and 8.7 m, and between 11.9 and 18.6 m in bedrock, consistent with measurements made in a 14.6 m deep borehole. The thermal model HYDRUS accurately predicted temperature dynamics at several monitored borehole depths. The success of the HYDRUS method indicates that the model can be a useful tool in predicting active layer temperatures and approximating ALTs in regions that are too difficult to install monitoring boreholes. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Rapidly rising sea temperatures off the western Antarctic Peninsula ( WAP) are placing the Antarctic benthos at risk of increasing predation from durophagous (shell-breaking) brachyuran and anomuran crabs. Crabs are at present excluded from Antarctic-shelf environments by their limited capacity to down-regulate magnesium ions in their blood, a constraint that paralyses and kills them under cold conditions. Interspecific variation in the ability of Subantarctic crabs to flush out magnesium ions predicts which species should be capable of extending their ranges to shelf environments along the Antarctic Peninsula. In agreement with those predictions, the brachyuran Halicarcinus planatus was recently found in the shallow subtidal zone at Deception Island, an emergent volcanic cone located off the WAP. Geothermal activity at Deception Island provides a warm-water opportunity for persistence in a cold ocean, and heavy ship-traffic there could accelerate the delivery of non-native species. Large populations of anomuran king crabs (Lithodidae) have recently been discovered on the continental slope off the WAP, at ambient sea temperatures slightly warmer than the waters over the shelf. The lithodids are generalized, durophagous predators that could expand to shelf habitats as the overlying waters warm rapidly. Another brachyuran, the globally invasive, durophagous European green crab Carcinus maenas, also appears poised to expand to nearshore habitats in Antarctica. Successful expansion of predators and other benthic species to the Antarctic shelf would accelerate the global trend towards functional homogenization of the marine biota. Long-term monitoring programmes should be established immediately to assess the extent of the problem in Antarctica. [ABSTRACT FROM AUTHOR]

Sixty-seven species of diatoms of 28 genera were identified in Core GC03-C2 acquired from the north slope of Elephant Island, Antarctic Peninsula. The number of diatom valves per gram of dry sediment ranged from 0.2∼17.3×10g, and these were dominated by Fragilariopsis kerguelensis (65.8%). Diatom assemblage analysis reconstructed the Quaternary paleoclimatic change the Elephant Islands. Four diatom assemblage zones were identified according to the frequency of critical taxa as follows: zone I, from 830 to 710 cm (Antarctic Cold Reversal); zone II, from 700 to 550 cm (Deglaciation zone); zone III, from 540 to 260 cm (warm period; Holocene); and zone IV, from 250 to 0 cm (cool period; Holocene). The high abundance of reworked species includes Actinocyclus ingens, Denticulopsis hustedtii, D. praedimorpha, and D. dimorpha appeared in Zone I by turbidity currents and ice rafting in the area during the glaciations-deglaciation event. [ABSTRACT FROM AUTHOR]

We show an annual overview of the sea-air CO2 exchanges and primary drivers in the Gerlache Strait, a hotspot for climate change that is ecologically important in the northern Antarctic Peninsula. In autumn and winter, episodic upwelling events increase the remineralized carbon in the sea surface, leading the region to act as a moderate or strong CO2 source to the atmosphere of up to 40 mmol m–2 day–1. During summer and late spring, photosynthesis decreases the CO2 partial pressure in the surface seawater, enhancing ocean CO2 uptake, which reaches values higher than − 40 mmol m–2 day–1. Thus, autumn/winter CO2 outgassing is nearly balanced by an only 4-month period of intense ocean CO2 ingassing during summer/spring. Hence, the estimated annual net sea-air CO2 flux from 2002 to 2017 was 1.24 ± 4.33 mmol m–2 day–1, opposing the common CO2 sink behaviour observed in other coastal regions around Antarctica. The main drivers of changes in the surface CO2 system in this region were total dissolved inorganic carbon and total alkalinity, revealing dominant influences of both physical and biological processes. These findings demonstrate the importance of Antarctica coastal zones as summer carbon sinks and emphasize the need to better understand local/regional seasonal sensitivity to the net CO2 flux effect on the Southern Ocean carbon cycle, especially considering the impacts caused by climate change. [ABSTRACT FROM AUTHOR]