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  • 1
    Publication Date: 2023-06-23
    Description: Antarctic sea ice prediction has garnered increasing attention in recent years, particularly in the context of the recent record lows of February 2022 and 2023. As Antarctica becomes a climate change hotspot, as polar tourism booms, and as scientific expeditions continue to explore this remote continent, the capacity to anticipate sea ice conditions weeks to months in advance is in increasing demand. Spurred by recent studies that uncovered physical mechanisms of Antarctic sea ice predictability and by the intriguing large variations of the observed sea ice extent in recent years, the Sea Ice Prediction Network South (SIPN South) project was initiated in 2017, building upon the Arctic Sea Ice Prediction Network. The SIPN South project annually coordinates spring-to-summer predictions of Antarctic sea ice conditions, to allow robust evaluation and intercomparison, and to guide future development in polar prediction systems. In this paper, we present and discuss the initial SIPN South results collected over six summer seasons (December-February 2017-2018 to 2022-2023). We use data from 22 unique contributors spanning five continents that have together delivered more than 3000 individual forecasts of sea ice area and concentration. The SIPN South median forecast of the circumpolar sea ice area captures the sign of the recent negative anomalies, and the verifying observations are systematically included in the 10-90% range of the forecast distribution. These statements also hold at the regional level except in the Ross Sea where the systematic biases and the ensemble spread are the largest. A notable finding is that the group forecast, constructed by aggregating the data provided by each contributor, outperforms most of the individual forecasts, both at the circumpolar and regional levels. This indicates the value of combining predictions to average out model-specific errors. Finally, we find that dynamical model predictions (i.e., based on process-based general circulation models) generally perform worse than statistical model predictions (i.e., data-driven empirical models including machine learning) in representing the regional variability of sea ice concentration in summer. SIPN South is a collaborative community project that is hosted on a shared public repository. The forecast and verification data used in SIPN South are publicly available in near-real time for further use by the polar research community, and eventually, policymakers.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 2
    Publication Date: 2023-04-17
    Description: We utilize a nudged simulation with the coupled regional atmosphere-ocean-sea ice model HIRHAM–NAOSIM over the Arctic to conduct an in-depth analysis of the impact of a sequence of three intense cyclones on the sea ice cover in the Barents and Kara Seas in February 2020. To clarify the underlying mechanisms we decompose changes in sea ice concentration (SIC) and thickness (SIT) into their dynamic and thermodynamic contributions and analyze them in concert with simulated changes in the wind forcing and the surface energy budget. Our findings reveal that changes in SIT during and after the cyclone passages are mostly driven by dynamic processes such as increased ice drift and deformation. With respect to SIC, the relative importance of dynamics and thermodynamics depends on the considered time scale and on the general conditions of the cyclone passages. If cyclones follow on each other in rapid succession, dynamic mechanisms dominate the SIC response for time scales of more than 2 weeks and thermodynamic effects via advection of warm-moist/cold-dry air masses on the cyclone’s front/back side only play a secondary role. However, if sufficiently long time elapses until the arrival of the next storm, thermodynamic SIC increase due to refreezing under the influence of cold and dry air at the backside of the cyclone becomes the dominating mechanism during the days following the cyclone passage.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 3
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    Frontiers Media SA
    In:  EPIC3Frontiers in Marine Science, Frontiers Media SA, 10, pp. 1082109-1082109, ISSN: 2296-7745
    Publication Date: 2023-03-24
    Description: In the past decades the Arctic has experienced stronger temperature increases than any other region globally. Shifts in hydrological regimes and accelerated permafrost thawing have been observed and are likely to increase mobilization of organic carbon and its transport through rivers into the Arctic Ocean. In order to better quantify changes to the carbon cycle, Arctic rivers such as the Lena River in Siberia need to be monitored closely. Since 2018, a sampling program provides frequent in situ observations of dissolved organic carbon (DOC) and colored dissolved organic matter (CDOM) of the Lena River. Here, we utilize this ground truth dataset and aim to test the potential of frequent satellite observations to spatially and temporally complement and expand these observations. We explored all available overpasses (~3250) of the Ocean and Land Colour Instrument (OLCI) on Sentinel-3 within the ice-free periods (May – October) for four years (2018 to 2021) to develop a new retrieval scheme to derive concentrations of DOC. OLCI observations with a spatial resolution of ~300 m were corrected for atmospheric effects using the Polymer algorithm. The results of this study show that using this new retrieval, remotely sensed DOC concentrations agree well with in situ DOC concentrations (MAPD=10.89%, RMSE=1.55 mg L−1, r²=0.92, n=489). The high revisit frequency and wide swath of OLCI allow it to capture the entire range of DOC concentrations and their seasonal variability. Estimated satellite-derived DOC export fluxes integrated over the ice-free periods of 2018 to 2021 show a high interannual variability and agree well with flux estimates from in situ data (RMSD=0.186 Tg C, MAPD=4.05%). In addition, 10-day OLCI composites covering the entire Lena River catchment revealed increasing DOC concentration and local sources of DOC along the Lena from south to north. We conclude that moderate resolution satellite imagers such as OLCI are very capable of observing DOC concentrations in large/wide rivers such as the Lena River despite the relatively coarse spatial resolution. The global coverage of remote sensing offers the expansion to more rivers in order to improve our understanding of the land-ocean carbon fluxes in a changing climate.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 4
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    Frontiers Media SA
    In:  Frontiers in Ecology and Evolution vol. 11 no. 1274762, pp. 1-19
    Publication Date: 2024-01-12
    Description: Modern humans are the only fully terrestrial ape. All other apes are \npartially arboreal, particularly as infants and juveniles. Precocial locomotor \ndevelopment, high frequency of arboreal locomotion in early ontogeny, and \nincreased terrestriality throughout development are ubiquitous amongst the \nhominines and likely represent the ancestral state. The role of climbing in \nhominin evolution has been debated for decades, but if hominins climbed \nregularly then subadults likely relied on it most frequently. Investigating the \nrole of climbing throughout hominin evolution requires reliable developmentally \nplastic traits that are responsive to locomotor loading and can be identified in the \nfossil record. Chimpanzees and gorillas provide a natural experiment to examine \nthe relationship between age-related variation locomotor activities and bone \nstructure. Chimpanzees and gorillas are most arboreal during infancy and \nbecome more terrestrial throughout development. Gorillas are comparatively \nmore terrestrial and transition to predominantly terrestrial locomotion at an \nearlier age. This paper has two main objectives. First, to examine if interspecific \ndifferences in the rate of locomotor development is reflected in bone structure. \nSecond, to determine if ontogenetic reductions in the frequency of arboreal \nlocomotion correspond to age-related variation in bone structure.
    Keywords: ontogeny ; locomotion ; primates ; hominin evolution ; bone ; life history
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
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  • 5
    Publication Date: 2023-03-09
    Description: 〈jats:p〉Sexually produced juvenile scleractinian corals play a key role in the adaptation process of coral reefs, as they are considered to possess an innate plasticity and thus can adjust to changing environmental parameters within a certain range. In this study we investigated in detail the early life stages of the brooding species 〈jats:italic〉Leptastrea purpurea〈/jats:italic〉 to identify, categorize and visualize the critical steps of the complex transformation process from a swimming coral larva to a sessile coral recruit and later to a coral colony. For that, we performed settlement experiments using previously known cues: cycloprodigiosin (CYPRO) and crustose coralline algae (CCA) as well as novel cues: crude extracts of 〈jats:italic〉Pseudoalteromonas espejiana〈/jats:italic〉 and 〈jats:italic〉P. piscicida〈/jats:italic〉 to identify a general, cue-independent settlement pathway. We monitored the development of 〈jats:italic〉L. purpurea〈/jats:italic〉 over 12 months using bright field and fluorescence microscopy. Also we identified the fluorescence signals of 〈jats:italic〉L. purpurea〈/jats:italic〉 with confocal microscopy at four crucial development steps: (A) swimming larva, (B) metamorphosing larva, (C) coral recruit and (D) adult coral. Our methodological approach allowed us to observe an ontogenetic shift of fluorescence signals which provokes the hypothesis that certain fluorescence patterns might be connected to distinct sequential functions in the early life cycle of scleractinian corals. Our observations showed great similarities to the early development of other brooding and spawning corals, making 〈jats:italic〉L. purpurea〈/jats:italic〉 a prospective candidate to be used as a model organism for coral research. Furthermore, our in-depth picture series provides a robust monitoring reference for coral nurseries or field applications and demonstrates the potential of fluorescence as an indicator to instantly determine the growth stage of a developing coral recruit.〈/jats:p〉
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 6
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    Frontiers Media SA
    In:  EPIC3Frontiers in Marine Science, Frontiers Media SA, 10, pp. 1092939-1092939, ISSN: 2296-7745
    Publication Date: 2023-03-06
    Description: 〈jats:p〉Plastic debris is ubiquitous in all ecosystems and has even reached locations that humans will hardly reach such as the deep ocean floor and the atmosphere. Research has highlighted that plastic debris is now pervasive even in remote Arctic regions. While modeling projections indicated local sources and long-distance transport as causes, empirical data about its origin and sources are scarce. Data collected by citizen scientists can increase the scale of observations, especially in such remote regions. Here, we report abundance and composition data of marine debris collected by citizen scientists on 14 remote Arctic beaches on the Spitsbergen archipelago. In addition, citizen scientists collected three large, industrial sized canvas bags (hereafter: big packs), filled with beached debris, of which composition, sources and origin were determined. A total debris mass of 1,620 kg was collected on about 38,000 m〈jats:sup〉2〈/jats:sup〉 (total mean = 41.83 g m〈jats:sup〉-2〈/jats:sup〉, SEM = ± 31.62). In terms of abundance, 23,000 pieces of debris were collected on 25,500 m〈jats:sup〉2〈/jats:sup〉 (total mean = 0.37 items of debris m〈jats:sup〉-2〈/jats:sup〉, SEM = ± 0.17). Although most items were plastic in both abundance and mass, fisheries waste, such as nets, rope, and large containers, dominated in mass (87%), and general plastics, such as packaging and plastic articles, dominated in abundance (80%). Fisheries-related debris points to local sea-based sources from vessels operating in the Arctic and nearby. General plastics could point to both land- and ship based sources, as household items are also used on ships and debris can be transported to the north 〈jats:italic〉via〈/jats:italic〉 the oceans current. Overall, 1% of the items (206 out of 14,707 pieces) collected in two big packs (2017 and 2021), bore imprints or labels allowing an analysis of their origin. If the categories ‘global’ and ‘English language’ were excluded, most of identifiable items originated from Arctic states (65%), especially from Russia (32%) and Norway (16%). But almost a third of the items (30%) was of European provenance, especially from Germany (8%). Five percent originated from more distant sources (e.g. USA, China, Korea, Brazil). Global measures such as an efficient and legally binding plastic treaty with improved upstream measures and waste management are urgently needed, to lower the amount of plastic entering our environments and in turn lifting the pressure on the Arctic region and its sensitive biota.〈/jats:p〉
    Repository Name: EPIC Alfred Wegener Institut
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  • 7
    Publication Date: 2024-01-03
    Description: As an expansion of a time-series study on meiobenthos in the Arctic deep sea, the diversity of free-living nematode communities along nine stations along a bathymetric transect was investigated morphologically in taxonomic and functional regards (feeding-type composition, life-history traits, tail-shape composition) and compared with previous studies of the same transect to investigate possible changes in the nematode community composition. Special emphasis was given on the analysis of sedimentary environmental parameters, which are used as proxies for food availability and sediment porosity. Multivariate statistics performed on nematode abundance data revealed a bathymetric zonation into four bathymetric zones: upper bathyal (1300 – 2000 m), lower bathyal (2500 - 3500 m), abyssal (5100 – 5600 m) and an additional ‘outgroup’ consisting of two stations with low nematode densities. Nematode densities generally decreased with increasing depth. Taxonomic diversity (EG〈jats:sub〉(50)〈/jats:sub〉, H’〈jats:sub〉(log2)〈/jats:sub〉, J’) decreased in a unimodal pattern peaking in the lower bathyal zone. A distance-based linear model revealed that 44% of the total variation in nematode abundances could be explained by the measured environmental parameters. Microbial feeders are the dominant feeding type along the transect with increasing dominance in the abyssal zone. The maturity index, a measure of environmental disturbance, decreased with depth, indicating a more colonizer-dominated community in the abyssal zone. Nematodes with long conico-cylindrical tails also become more dominant in the abyssal zone. A previous study of the same transect conducted in 2005 found a similar bathymetric zonation, but with a strikingly different dominant feeding type, i.e. epistrate feeders. Between the 2005 study and the year 2010 we conducted our study, the composition of the plankton community in the Fram Strait changed significantly due to a warm water anomaly in the region. We argue that through bentho-pelagic coupling, effects of this warm water anomaly on plankton communities could be a reason for the drastic change in dominant nematode feeding types.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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