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Tifenn Le Bris, Guilhem Barruol, Emmanuel Le Meur, Florent Gimbert, Dimitri Zigone. (2023). Monitoring the cryoseismic activity of the Astrolabe glacier, Terre Adélie, Antarctica (Vol. EGU23-7489).
Abstract: In coastal Antarctica, outlet glaciers exhibit complex dynamics materialized by intense internal deformation, enhanced basal sliding and strong thermo-mechanical interactions with the ocean. Here we aim to use seismic observations to unravel these various processes and their link with glacier and ocean dynamics. As part of the SEIS-ADELICE project (2020-2024) supported by the French Polar Institute IPEV, in January 2022 we deployed four permanent and six temporary (1 month long) broadband seismic stations on and around the Astrolabe Glacier (Terre Adélie, East Antarctica), as well as four ocean-bottom seismometers at sea near the terminus of the floating tongue. In January 2023 we will be supplementing this setup by a temporary network of 50 seismic nodes above the grounding line of the glacier.
Preliminary detection and classification of seismic events reveals a wide variety of cryo-seismic signals. The most pervasive events correspond to icequakes, are located close to the surface, and exhibit clear tidal modulation. We interpret these events as being generated by the brittle fracturing of ice associated with crevasse opening. We also observe numerous short and similar repetitive events of much lower amplitude that are located at few restricted locations near the ice-bedrock interface. These events are likely produced by basal stick-slip over punctual bedrock asperities. Finally, we observe glacial tremors which could result from hydraulic sources at the ice-bedrock interface, although further analysis is required to confirm this hypothesis.
This preliminary work provides useful grounds for deeper analysis to be done in the future on source characteristics and their more quantitative links with glacier dynamics.
Programme: 411
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Jens Zinke, Juan P. D'Olivo, Christoph J. Gey, Malcolm T. McCulloch, J. Henrich Bruggemann, Janice M. Lough, Mireille M. M. Guillaume. (2019). Multi-trace-element sea surface temperature coral reconstruction for the southern Mozambique Channel reveals teleconnections with the tropical Atlantic (Vol. 16).
Abstract: Abstract. Here we report seasonally resolved sea surface temperatures for the southern Mozambique Channel in the SW Indian Ocean based on multi-trace-element temperature proxy records preserved in two Porites sp. coral cores. Particularly, we assess the suitability of both separate and combined Sr∕Ca and Li∕Mg proxies for improved multielement SST reconstructions. Overall, geochemical records from Europa Island Porites sp. highlight the potential of Sr∕Ca and Li∕Mg ratios as high-resolution climate proxies but also show significant differences in their response at this Indian Ocean subtropical reef site. Our reconstruction from 1970 to 2013 using the Sr∕Ca SST proxy reveals a warming trend of 0.58±0.1 ∘C in close agreement with instrumental data (0.47±0.07 ∘C) over the last 42 years (1970–2013). In contrast, the Li∕Mg showed unrealistically large warming trends, most probably caused by uncertainties around different uptake mechanisms of the trace elements Li and Mg and uncertainties in their temperature calibration. In our study, Sr∕Ca is superior to Li∕Mg to quantify absolute SST and relative changes in SST. However, spatial correlations between the combined detrended Sr∕Ca and Li∕Mg proxies compared to instrumental SST at Europa revealed robust correlations with local climate variability in the Mozambique Channel and teleconnections to regions in the Indian Ocean and southeastern Pacific where surface wind variability appeared to dominate the underlying pattern of SST variability. The strongest correlation was found between our Europa SST reconstruction and instrumental SST records from the northern tropical Atlantic. Only a weak correlation was found with ENSO, with recent warm anomalies in the geochemical proxies coinciding with strong El Niño or La Niña. We identified the Pacific–North American (PNA) atmospheric pattern, which develops in the Pacific in response to ENSO, and the tropical North Atlantic SST as the most likely causes of the observed teleconnections with the Mozambique Channel SST at Europa.
Programme: 688
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Philippe Ricaud, Massimo Del Guasta, Eric Bazile, Niramson Azouz, Angelo Lupi, Pierre Durand, Jean-Luc Attié, Dana Veron, Vincent Guidard, Paolo Grigioni. (2020). Supercooled liquid water cloud observed, analysed, and modelled at the top of the planetary boundary layer above Dome C, Antarctica (Vol. 20).
Abstract: Abstract. A comprehensive analysis of the water budget over the Dome C (Concordia, Antarctica) station has been performed during the austral summer 2018–2019 as part of the Year of Polar Prediction (YOPP) international campaign. Thin (∼100 m deep) supercooled liquid water (SLW) clouds have been detected and analysed using remotely sensed observations at the station (tropospheric depolarization lidar, the H2O Antarctica Microwave Stratospheric and Tropospheric Radiometer (HAMSTRAD), net surface radiation from the Baseline Surface Radiation Network (BSRN)), radiosondes, and satellite observations (CALIOP, Cloud-Aerosol LIdar with Orthogonal Polarization/CALIPSO, Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations) combined with a specific configuration of the numerical weather prediction model: ARPEGE-SH (Action de Recherche Petite Echelle Grande Echelle – Southern Hemisphere). The analysis shows that SLW clouds were present from November to March, with the greatest frequency occurring in December and January when ∼50 % of the days in summer time exhibited SLW clouds for at least 1 h. Two case studies are used to illustrate this phenomenon. On 24 December 2018, the atmospheric planetary boundary layer (PBL) evolved following a typical diurnal variation, which is to say with a warm and dry mixing layer at local noon thicker than the cold and dry stable layer at local midnight. Our study showed that the SLW clouds were observed at Dome C within the entrainment and the capping inversion zones at the top of the PBL. ARPEGE-SH was not able to correctly estimate the ratio between liquid and solid water inside the clouds with the liquid water path (LWP) strongly underestimated by a factor of 1000 compared to observations. The lack of simulated SLW in the model impacted the net surface radiation that was 20–30 W m−2 higher in the BSRN observations than in the ARPEGE-SH calculations, mainly attributable to the BSRN longwave downward surface radiation being 50 W m−2 greater than that of ARPEGE-SH. The second case study took place on 20 December 2018, when a warm and wet episode impacted the PBL with no clear diurnal cycle of the PBL top. SLW cloud appearance within the entrainment and capping inversion zones coincided with the warm and wet event. The amount of liquid water measured by HAMSTRAD was ∼20 times greater in this perturbed PBL than in the typical PBL. Since ARPEGE-SH was not able to accurately reproduce these SLW clouds, the discrepancy between the observed and calculated net surface radiation was even greater than in the typical PBL case, reaching +50 W m−2, mainly attributable to the downwelling longwave surface radiation from BSRN being 100 W m−2 greater than that of ARPEGE-SH. The model was then run with a new partition function favouring liquid water for temperatures below −20 down to −40 ∘C. In this test mode, ARPEGE-SH has been able to generate SLW clouds with modelled LWP and net surface radiation consistent with observations during the typical case, whereas, during the perturbed case, the modelled LWP was 10 times less than the observations and the modelled net surface radiation remained lower than the observations by ∼50 W m−2. Accurately modelling the presence of SLW clouds appears crucial to correctly simulate the surface energy budget over the Antarctic Plateau.
Programme: 910
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Hans-Werner Jacobi, Friedrich Obleitner, Sophie Da Costa, Patrick Ginot, Konstantinos Eleftheriadis, Wenche Aas, Marco Zanatta. (2019). Deposition of ionic species and black carbon to the Arctic snowpack: combining snow pit observations with modeling (Vol. 19).
Abstract: Abstract. Although aerosols in the Arctic have multiple and complex impacts on the regional climate, their removal due to deposition is still not well quantified. We combined meteorological, aerosol, precipitation, and snowpack observations with simulations to derive information about the deposition of sea salt components and black carbon (BC) from November 2011 to April 2012 to the Arctic snowpack at two locations close to Ny-Ålesund, Svalbard. The dominating role of sea salt and the contribution of dust for the composition of atmospheric aerosols were reflected in the seasonal composition of the snowpack. The strong alignment of the concentrations of the major sea salt components in the aerosols, the precipitation, and the snowpack is linked to the importance of wet deposition for transfer from the atmosphere to the snowpack. This agreement was less strong for monthly snow budgets and deposition, indicating important relocation of the impurities inside the snowpack after deposition. Wet deposition was less important for the transfer of nitrate, non-sea-salt sulfate, and BC to the snow during the winter period. The average BC concentration in the snowpack remains small, with a limited impact on snow albedo and melting. Nevertheless, the observations also indicate an important redistribution of BC in the snowpack, leading to layers with enhanced concentrations. The complex behavior of bromide due to modifications during sea salt aerosol formation and remobilization in the atmosphere and in the snow were not resolved because of the lack of bromide measurements in aerosols and precipitation.
Programme: 1126
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Marco Zanatta, Paolo Laj, Martin Gysel, Urs Baltensperger, Stergios Vratolis, Konstantinos Eleftheriadis, Yutaka Kondo, Philippe Dubuisson, Victor Winiarek, Stelios Kazadzis, Peter Tunved, Hans-Werner Jacobi. (2018). Effects of mixing state on optical and radiative properties of black carbon in the European Arctic (Vol. 18).
Abstract: Abstract. Atmospheric aging promotes internal mixing of black carbon (BC), leading to an enhancement of light absorption and radiative forcing. The relationship between BC mixing state and consequent absorption enhancement was never estimated for BC found in the Arctic region. In the present work, we aim to quantify the absorption enhancement and its impact on radiative forcing as a function of microphysical properties and mixing state of BC observed in situ at the Zeppelin Arctic station (78∘ N) in the spring of 2012 during the CLIMSLIP (Climate impacts of short-lived pollutants in the polar region) project. Single-particle soot photometer (SP2) measurements showed a mean mass concentration of refractory black carbon (rBC) of 39 ng m−3, while the rBC mass size distribution was of lognormal shape, peaking at an rBC mass-equivalent diameter (DrBC) of around 240 nm. On average, the number fraction of particles containing a BC core with DrBC>80 nm was less than 5 % in the size range (overall optical particle diameter) from 150 to 500 nm. The BC cores were internally mixed with other particulate matter. The median coating thickness of BC cores with 220 nm < DrBC< 260 nm was 52 nm, resulting in a core–shell diameter ratio of 1.4, assuming a coated sphere morphology. Combining the aerosol absorption coefficient observed with an Aethalometer and the rBC mass concentration from the SP2, a mass absorption cross section (MAC) of 9.8 m2 g−1 was inferred at a wavelength of 550 nm. Consistent with direct observation, a similar MAC value (8.4 m2 g−1 at 550 nm) was obtained indirectly by using Mie theory and assuming a coated-sphere morphology with the BC mixing state constrained from the SP2 measurements. According to these calculations, the lensing effect is estimated to cause a 54 % enhancement of the MAC compared to that of bare BC particles with equal BC core size distribution. Finally, the ARTDECO radiative transfer model was used to estimate the sensitivity of the radiative balance to changes in light absorption by BC as a result of a varying degree of internal mixing at constant total BC mass. The clear-sky noontime aerosol radiative forcing over a surface with an assumed wavelength-dependent albedo of 0.76–0.89 decreased, when ignoring the absorption enhancement, by −0.12 W m−2 compared to the base case scenario, which was constrained with mean observed aerosol properties for the Zeppelin site in Arctic spring. The exact magnitude of this forcing difference scales with environmental conditions such as the aerosol optical depth, solar zenith angle and surface albedo. Nevertheless, our investigation suggests that the absorption enhancement due to internal mixing of BC, which is a systematic effect, should be considered for quantifying the aerosol radiative forcing in the Arctic region.
Programme: 1126
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Hélène Angot, Olivier Magand, Detlev Helmig, Philippe Ricaud, Boris Quennehen, Hubert Gallée, Massimo Del Guasta, Francesca Sprovieri, Nicola Pirrone, Joël Savarino, Aurélien Dommergue. (2016). New insights into the atmospheric mercury cycling in central Antarctica and implications on a continental scale (Vol. 16).
Abstract: Abstract. Under the framework of the GMOS project (Global Mercury Observation System) atmospheric mercury monitoring has been implemented at Concordia Station on the high-altitude Antarctic plateau (75°06′S, 123°20′E, 3220m above sea level). We report here the first year-round measurements of gaseous elemental mercury (Hg(0)) in the atmosphere and in snowpack interstitial air on the East Antarctic ice sheet. This unique data set shows evidence of an intense oxidation of atmospheric Hg(0) in summer (24-hour daylight) due to the high oxidative capacity of the Antarctic plateau atmosphere in this period of the year. Summertime Hg(0) concentrations exhibited a pronounced daily cycle in ambient air with maximal concentrations around midday. Photochemical reactions and chemical exchange at the air–snow interface were prominent, highlighting the role of the snowpack on the atmospheric mercury cycle. Our observations reveal a 20 to 30% decrease of atmospheric Hg(0) concentrations from May to mid-August (winter, 24h darkness). This phenomenon has not been reported elsewhere and possibly results from the dry deposition of Hg(0) onto the snowpack. We also reveal the occurrence of multi-day to weeklong atmospheric Hg(0) depletion events in summer, not associated with depletions of ozone, and likely due to a stagnation of air masses above the plateau triggering an accumulation of oxidants within the shallow boundary layer. Our observations suggest that the inland atmospheric reservoir is depleted in Hg(0) in summer. Due to katabatic winds flowing out from the Antarctic plateau down the steep vertical drops along the coast and according to observations at coastal Antarctic stations, the striking reactivity observed on the plateau most likely influences the cycle of atmospheric mercury on a continental scale.
Programme: 1013
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Fabienne Joliet, Véronique Van Tilbeurgh, Anne Atlan. (2020). La valeur d’existence du monde vivant selon les Inuits du Nunavik et les Occidentaux aux Kerguelen (Vol. 732).
Abstract: Dans le contexte actuel de transition socio-écologique internationale, l’objectif de cet article est d’interroger la relation entre les humains et les autres vivants et choses naturelles dans les derniers espaces de vaste naturalité aux pôles. C’est à travers la notion de valeur d’existence que cette relation sera analysée dans ses retranchements chez les Inuits qui habitent le Nunavik en subarctique et les Occidentaux qui veillent sur les Kerguelen en subantarctique. Plus particulièrement, c’est la nature du lien qu’ils entretiennent avec les vivants non-humains et autres choses naturelles, et ses registres de valeurs qui sont étudiées.Ces enquêtes boréales et australes en zone protégée ou bien à ses abords montrent ainsi que ce qui prédomine, c’est le fait qu’il est attribué aux éléments naturels une valeur d’existence en fonction d’un esprit commun spirituel ou bien d’une enveloppe commune charnelle d’« être vivant ». Selon ces principes, les modalités prises par l’attribution de la valeur d’existence changent : les humains se concevant soit, comme une partie d’un ensemble au même titre que les autres vivants et choses naturelles ayant un esprit ou conscience, soit comme maîtres et protecteurs des autres vivants et choses naturelles, en tant qu’ayant une fonction dominante au sein d’« êtres vivants ». Dans cette perspective, le territoire joue un rôle spécifique favorisant l’existence même de cette valeur au-delà de ses fonctions de régulation couramment retenues.
Programme: 136
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Laura Andrea Alfaro Garcia, Sébastien Descamps, Dorte Herzke, Olivier Chastel, Alice Carravieri, Yves Cherel, Pierre Labadie, Hélène Budzinski, Gabriel Munoz, Paco Bustamante, Anuschka Polder, Geir Wing Gabrielsen, Jan Ove Bustnes, Katrine Borgå. (2022). Bioaccumulation of Per and Polyfluoroalkyl Substances in Antarctic Breeding South Polar Skuas (Catharacta maccormicki) and Their Prey (Vol. 9).
Abstract: Per and polyfluoroalkyl substances (PFASs) are found in Antarctic wildlife, with high levels in the avian top predator south polar skua (Catharacta maccormicki). As increasing PFAS concentrations were found in the south polar skua during the breeding season in Antarctica, we hypothesised that available prey during the breeding period contributes significantly to the PFAS contamination in skuas. To test this, we compared PFAS in south polar skuas and their main prey from two breeding sites on opposite sides of the Antarctic continent: Antarctic petrel (Thalassoica antarctica) stomach content, eggs, chicks, and adults from Svarthamaren in Dronning Maud Land and Adélie penguin chicks (Pygoscelis adeliae) from Dumont d’Urville in Adélie Land. Of the 22 PFAS analysed, seven were present in the majority of samples, except petrel stomach content [only perfluoroundecanoate (PFUnA) present] and Adélie penguins (only four compounds present), with increasing concentrations from the prey to the skuas. The biomagnification factors (BMFs) were higher at Dumont d’Urville than Svarthamaren. When adjusted to reflect one trophic level difference, the BMFs at Svarthamaren remained the same, whereas the ones at Dumont d’Urville doubled. At both the colonies, the skua PFAS pattern was dominated by perfluorooctanesulfonic acid (PFOS), followed by PFUnA, but differed with the presence of branched PFOS and perfluorotetradecanoate (PFTeA) and lack of perfluorononanoate (PFNA) and perfluorodecanoate (PFDA) at Dumont d’Urville. At Svarthamaren, the pattern in the prey was comparable to the skuas, but with a higher relative contribution of PFTeA in prey. At Dumont d’Urville, the pattern in the prey differed from the skuas, with the domination of PFUnA and the general lack of PFOS in prey. Even though the PFAS levels are low in Antarctic year-round resident prey, the three lines of evidence (pattern, BMF difference, and BMF adjusted to one trophic level) suggest that the Antarctic petrel are the significant source of PFAS in the Svarthamaren skuas, whereas the skuas in Dumont d’Urville have other important sources to PFAS than Adélie penguin, either in the continent or external on the inter-breeding foraging grounds far from Antarctica.
Programme: 109
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Petra Quillfeldt, Yves Cherel, Joan Navarro, Richard A. Phillips, Juan F. Masello, Cristián G. Suazo, Karine Delord, Paco Bustamante. (2022). Variation Among Species and Populations, and Carry-Over Effects of Winter Exposure on Mercury Accumulation in Small Petrels (Vol. 10).
Abstract: Even in areas as remote as the Southern Ocean, marine organisms are exposed to contaminants that arrive through long-range atmospheric transport, such as mercury (Hg), a highly toxic metal. In previous studies in the Southern Ocean, inter-specific differences in Hg contamination in seabirds was generally related to their distribution and trophic position. However, the Blue Petrel (Halobaena caerulea) was a notable exception among small seabirds, with higher Hg levels than expected. In this study, we compared the Hg contamination of Blue Petrels and Thin-billed Prions (Pachyptila belcheri), which both spend the non-breeding season in polar waters, with that of Antarctic Prions (Pachyptila desolata), which spend the winter in subtropical waters. We collected body feathers and blood samples, representing exposure during different time-frames. Hg concentrations in feathers, which reflect contamination throughout the annual cycle, were related to δ13C values, and varied with ocean basin and species. Blue Petrels from breeding colonies in the southeast Pacific Ocean had much higher feather Hg concentrations than expected after accounting for latitude and their low trophic positions. Both Hg concentrations and δ15N in blood samples of Blue Petrels were much lower at the end than at the start of the breeding period, indicating a marked decline in Hg contamination and trophic positions, and the carry-over of Hg burdens between the wintering and breeding periods. Elevated Hg levels may reflect greater reliance on myctophids or foraging in sea-ice environments. Our study underlines that carry-over of Hg concentrations in prey consumed in winter may determine body Hg burdens well into the breeding season.
Programme: 109
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Andrea Spolaor, Beatrice Moroni, Bartłomiej Luks, Adam Nawrot, Marco Roman, Catherine Larose, Łukasz Stachnik, Federica Bruschi, Krystyna Kozioł, Filip Pawlak, Clara Turetta, Elena Barbaro, Jean-Charles Gallet, David Cappelletti. (2021). Investigation on the Sources and Impact of Trace Elements in the Annual Snowpack and the Firn in the Hansbreen (Southwest Spitsbergen) (Vol. 8).
Abstract: We present a thorough evaluation of the water soluble fraction of the trace element composition (Ca, Sr, Mg, Na, K, Li, B, Rb, U, Ni, Co, As, Cs, Cd, Mo, Se, Eu, Ba, V, Ge, Ga, Cr, Cr, P, Ti, Mn, Zr, Ce, Zn, Fe, Gd, Y, Pb, Bi, Yb, Al, Nb, Er, Nd, Dy, Sm, Ho, Th, La, Lu, Tm, Pr, Tb, Fe, In, Tl) and their fluxes in the annual snowpack and the firn of the Hansbreen (a tidewater glacier terminating in the Hornsund fjord, southwest Spitsbergen). The trace element samples were obtained from a 3 m deep snow pit dug at the plateau of the glacier (450 m a.s.l.), and from a 2 m deep firn core collected from the bottom of the snow pit. The comparison of elemental fluxes and enrichment factors allowed us to constrain specific summer and wintertime deposition patterns of water soluble trace elements in the southern part of the Svalbard archipelago. Our results suggest that the chemical composition of the Hansbreen (and likely other glaciers where the summit is close to the equilibrium line) is mainly affected by summertime deposition of trace elements from local sources and some volatile elements, which may be transported into the Arctic when polar vortex is weak. The melting of the annual snowpack seems to have a minor influence on the overall chemical signature of the glacier ice.
Programme: 1192
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