Morten Frederiksen, Olivier Gilg, Glenn Yannic. (2021). Cross-icecap spring migration confirmed in a high-Arctic seabird, the Ivory Gull Pagophila eburnea (Vol. 163).
Abstract: Seabirds rarely cross major terrestrial barriers during seasonal migration, possibly because they have a limited ability to build up fat stores. For the first time, we tracked two Ivory Gulls with GPS loggers during spring migration from the wintering area in Davis Strait to the breeding colony in north-east Greenland. While one bird migrated in March around the southern tip of Greenland, the other delayed migration until May and crossed the Greenland icecap north of 70°N, covering 1345 km in 29 h. Several aspects of the crossing were noteworthy: the track was remarkably direct, the bird made several stops (totalling 6 h) on the icecap, and the bird increased its flying altitude to nearly 3000 m over West Greenland and > 4000 m over East Greenland.
Keywords: ecological barrier Greenland icecap high-altitude migration
Programme: 1210
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Juan Pedro Rodríguez-López, Brigitte Van Vliet-Lanoë, Jerónimo López-Martínez, Rebeca Martín-García. (2021). Scouring by rafted ice and cryogenic patterned ground preserved in a Palaeoproterozoic equatorial proglacial lagoon succession, eastern India, Nuna supercontinent (Vol. 123).
Abstract: The Chaibasa Formation contains the oldest known record of ploughmarks formed by rafted ice preserved on Earth. The Palaeoproterozoic (Orosirian-Rhyacian, 1.86–2.1 Ga) Chaibasa Formation in the Dhalbhumgarh area, eastern India, represents sedimentation in an ice-contact proglacial lagoon affected by iceberg (bits and growlers) calving and lake-ice rafting. Ice scouring, both on muddy and sandy substrates, as well as ice “rosettes” developed as consequence of the ploughing action of floating icebergs that were moved by wind, meltwater floods and tidal currents on soft sediments. Muddy flats surrounding the proglacial lagoon underwent seasonal deep freezing conditions developing cryogenic patterned ground containing reticulate ice, ice veins and sand wedges, suggesting the occurrence of proglacial permafrost areas coeval with Proterozoic glaciers. The central part of the proglacial lagoon was characterized by deposition of glacial varves punctuated by pebble and cobble size angular dropstones accumulated in the basin as ice-rafted debris from floating ice. Evidences provided in this paper reinforced the idea that 1.86–2.1 Ga ago glacial conditions prevailed after the supposed ending of the Huronian glaciation. This paper provides detailed examples that can be used to recognize possible floating/drifted ice scours in other Precambrian successions, as these elements have largely passed undetected, being probably widely reported in the literature as generic soft-sediment deformation structures. Similar soft-sediment deformations from Precambrian clastic depositional systems should be re-evaluated as there is a significant possibility that most of the Precambrian iceberg-related structures had escape notice, as originally suggested Eyles et al. in 1997.
Keywords: Ice-rafted debris Iceberg scouring India Palaeoproterozoic Permafrost Proglacial Reticulate ice
Programme: 316
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Christophe Barbraud, Baudouin des Monstiers, Adrien Chaigne, Cédric Marteau, Henri Weimerskirch, Karine Delord. (2021). Predation by feral cats threatens great albatrosses (Vol. 23).
Abstract: Feral cats (Felis catus) are a potential threat for several seabird species including medium sized albatrosses, but studies documenting predation behavior, demographic impacts and effects of predator control are scarce. Here, we present data on feral cat predation behavior on one of the world’s largest seabirds, the wandering albatross (Diomedea exulans) at Kerguelen Island, and show how it affects breeding success and rate of population growth. We assess the effect of a feral cat control experiment on breeding success and population viability. Using 32 camera traps we monitored 25 nests of albatross and detected 295 events showing a potential predator. Of these, 75.2% and 24.8% involved feral cats and giant petrels, respectively. Giant petrels were never implicated in direct predation. We recorded 17 attacks of feral cats on 13 albatross chicks. Attacks lasted in average 52.1 ± 72.9 min, and resulted in the death of 10 of the 13 (76.9%) monitored chicks. Breeding success where attacks were recorded was low (12%) compared to areas with no attack (86%). Mean breeding success during 3 years before cat control was 26% and increased to 80% during the 3 years following the experiment. According to predation scenarios, population modelling showed that the albatross population would decline by 2.7–4.5% per year without cat control. Following cat control the population would increase at 1.8% per year. Our results demonstrate that feral cats predate and have negative impacts on breeding success and population growth rate of wandering albatrosses at Kerguelen Island. We provide recommendations on feral cat control and eradication to mitigate the risk of population decline or local extinction of large albatrosses.
Programme: 109
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Ryo Okuwaki, Stephen P. Hicks, Timothy J. Craig, Wenyuan Fan, Saskia Goes, Tim J. Wright, Yuji Yagi. (2021). Illuminating a Contorted Slab With a Complex Intraslab Rupture Evolution During the 2021 Mw 7.3 East Cape, New Zealand Earthquake (Vol. 48).
Abstract: The state-of-stress within subducting oceanic plates controls rupture processes of deep intraslab earthquakes. However, little is known about how the large-scale plate geometry and the stress regime relate to the physical nature of the deep intraslab earthquakes. Here we find, by using globally and locally observed seismic records, that the moment magnitude 7.3 2021 East Cape, New Zealand earthquake was driven by a combination of shallow trench-normal extension and unexpectedly, deep trench-parallel compression. We find multiple rupture episodes comprising a mixture of reverse, strike-slip, and normal faulting. Reverse faulting due to the trench-parallel compression is unexpected given the apparent subduction direction, so we require a differential buoyancy-driven stress rotation, which contorts the slab near the edge of the Hikurangi plateau. Our finding highlights that buoyant features in subducting plates may cause diverse rupture behavior of intraslab earthquakes due to the resulting heterogeneous stress state within slabs.
Keywords: earthquake rupture finite-fault inversion Hikurangi intraslab earthquakes slab geometry source imaging
Programme: 133
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Crouzet N. (2021). Monitoring warm transiting exoplanets for Ariel with ASTEP+.
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Akers P., Savarino, J., Caillon, N. (2021). Reconstructing Antarctic snow accumulation using nitrogen isotopes of nitrate.
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Barbero A., Grilli R., Blouzon C., Ahmed S., Thomas J.L., Frey M., Huang Y., Caillon N., Savarino J. (2021). Innovative approach for new estimation of NOx snow-source on the Antarctic Plateau.
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G. Hubert, S. Aubry. (2021). Study of the Impact of Past Extreme Solar Events on the Modern Air Traffic (Vol. 19).
Abstract: The ancient solar energetic particle (SEP) events of 774/775 CE and 993/994 CE were characterized thanks to radionuclide productions stored in environmental archives as ice cores or tree rings. Primary cosmic ray spectra deduced from these cosmogenic isotope data indicate that the impact of these extreme SEP events would have been much more significant than any of the ones observed during the modern era. However, the impact of these should be studied more accurately in the framework of the ambient dose equivalent impacting aircrew and passengers in the air traffic context by considering physical parameters such as time profile or anisotropy properties. In this study, the impact that 774/775 CE and 993/994 CE past extreme SEP events could have had on modern air traffic is discussed. Possible event spectra for these ancient events are derived from the spectra ground-level enhancement (GLE) 5 and GLE 69, which have been observed during the modern era and have been widely studied/characterized using measurements. The investigations include the impact of the SEP activity on ambient dose equivalent, including detailed analyses considering route, airplane characteristics (departure, arrival, continent, airplane type), and the time occurrence of the SEP event. Statistical analyses show that additional dose levels can reach values on the order of 70 mSv, which is absolutely significant considering the current air traffic recommendations. The orders of magnitude of the ambient dose equivalent induced during past extreme SEP events raises a number of issues, both for aircrews and for avionics hardware. This study demonstrates that simulations can be useful for the evaluation of risks in case of extreme SEP events.
Programme: 1112
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P. Alken, E. Thébault, C. D. Beggan, J. Aubert, J. Baerenzung, W. J. Brown, S. Califf, A. Chulliat, G. A. Cox, C. C. Finlay, A. Fournier, N. Gillet, M. D. Hammer, M. Holschneider, G. Hulot, M. Korte, V. Lesur, P. W. Livermore, F. J. Lowes, S. Macmillan, M. Nair, N. Olsen, G. Ropp, M. Rother, N. R. Schnepf, C. Stolle, H. Toh, F. Vervelidou, P. Vigneron, I. Wardinski. (2021). Evaluation of candidate models for the 13th generation International Geomagnetic Reference Field (Vol. 73).
Abstract: In December 2019, the 13th revision of the International Geomagnetic Reference Field (IGRF) was released by the International Association of Geomagnetism and Aeronomy (IAGA) Division V Working Group V-MOD. This revision comprises two new spherical harmonic main field models for epochs 2015.0 (DGRF-2015) and 2020.0 (IGRF-2020) and a model of the predicted secular variation for the interval 2020.0 to 2025.0 (SV-2020-2025). The models were produced from candidates submitted by fifteen international teams. These teams were led by the British Geological Survey (UK), China Earthquake Administration (China), Universidad Complutense de Madrid (Spain), University of Colorado Boulder (USA), Technical University of Denmark (Denmark), GFZ German Research Centre for Geosciences (Germany), Institut de physique du globe de Paris (France), Institut des Sciences de la Terre (France), Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (Russia), Kyoto University (Japan), University of Leeds (UK), Max Planck Institute for Solar System Research (Germany), NASA Goddard Space Flight Center (USA), University of Potsdam (Germany), and Université de Strasbourg (France). The candidate models were evaluated individually and compared to all other candidates as well to the mean, median and a robust Huber-weighted model of all candidates. These analyses were used to identify, for example, the variation between the Gauss coefficients or the geographical regions where the candidate models strongly differed. The majority of candidates were sufficiently close that the differences can be explained primarily by individual modeling methodologies and data selection strategies. None of the candidates were so different as to warrant their exclusion from the final IGRF-13. The IAGA V-MOD task force thus voted for two approaches: the median of the Gauss coefficients of the candidates for the DGRF-2015 and IGRF-2020 models and the robust Huber-weighted model for the predictive SV-2020-2025. In this paper, we document the evaluation of the candidate models and provide details of the approach used to derive the final IGRF-13 products. We also perform a retrospective analysis of the IGRF-12 SV candidates over their performance period (2015–2020). Our findings suggest that forecasting secular variation can benefit from combining physics-based core modeling with satellite observations.
Keywords: Geomagnetism IGRF Magnetic field modeling
Programme: 139
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Alexandre Corbeau, Julien Collet, Adrien Pajot, Rocío Joo, Thibaut Thellier, Henri Weimerskirch. (2021). Differences in foraging habitat result in contrasting fisheries interactions in two albatross populations (Vol. 663).
Abstract: Albatrosses attend fishing boats to feed on fishing discards but are often at risk of accidental bycatch. To examine whether populations (same species) and sexes differ in their overlap with fisheries due to differences in habitat use, we combined the use of recently developed loggers equipped with GPS and boat radar detectors with Automatic Identification System (AIS) data. Our study indicates that incubating wandering albatrosses Diomedea exulans from Crozet and Kerguelen foraged in different habitats although the duration of trips was similar. Both female and male Kerguelen birds took advantage of the large and productive surrounding shelf, whereas Crozet birds used the small shelf around the islands to a lesser extent. In Crozet, there was segregation between males and females, the latter favouring deeper and warmer waters. The 2 strategies of habitat use led to different overlap and attraction to boats, with Kerguelen birds encountering and attending boats for longer and at closer proximity to the colony than Crozet birds. Crozet females encountered boats at greater distances from the colony than males. Because of their different habitat use and foraging outside exclusive economic zones (EEZ) and further from the colony, Crozet birds attended more non-declared boats (without AIS) than Kerguelen birds. Albatrosses were more attracted by fisheries than cargo vessels and were especially attracted by fishing discards that led them to attend vessels for longer periods for both sexes and populations. The differences found between populations and individuals in terms of habitat specialization and encounter rate of fisheries should be considered for future assessments of risk of bycatch.
Keywords: Boat attraction Crozet Diomedea exulans Fisheries Fisheries discards Kerguelen
Programme: 109
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