| Records |
| Author |
Étienne Vignon, Ghislain Picard, Claudio Durán-Alarcón, Simon P. Alexander, Hubert Gallée, Alexis Berne |
| Title |
Gravity Wave Excitation during the Coastal Transition of an Extreme Katabatic Flow in Antarctica |
Type |
Journal |
| Year |
2020 |
Publication |
Journal of the Atmospheric Sciences |
Abbreviated Journal |
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| Volume |
77 |
Issue |
4 |
Pages |
1295-1312 |
| Keywords |
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| Abstract |
The offshore extent of Antarctic katabatic winds exerts a strong control on the production of sea ice and the formation of polynyas. In this study, we make use of a combination of ground-based remotely sensed and meteorological measurements at Dumont d’Urville (DDU) station, satellite images, and simulations with the Weather Research and Forecasting Model to analyze a major katabatic wind event in Adélie Land. Once well developed over the slope of the ice sheet, the katabatic flow experiences an abrupt transition near the coastal edge consisting of a sharp increase in the boundary layer depth, a sudden decrease in wind speed, and a decrease in Froude number from 3.5 to 0.3. This so-called katabatic jump manifests as a turbulent “wall” of blowing snow in which updrafts exceed 5 m s−1. The wall reaches heights of 1000 m and its horizontal extent along the coast is more than 400 km. By destabilizing the boundary layer downstream, the jump favors the trapping of a gravity wave train—with a horizontal wavelength of 10.5 km—that develops in a few hours. The trapped gravity waves exert a drag that considerably slows down the low-level outflow. Moreover, atmospheric rotors form below the first wave crests. The wind speed record measured at DDU in 2017 (58.5 m s−1) is due to the vertical advection of momentum by a rotor. A statistical analysis of observations at DDU reveals that katabatic jumps and low-level trapped gravity waves occur frequently over coastal Adélie Land. It emphasizes the important role of such phenomena in the coastal Antarctic dynamics. |
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| ISSN |
0022-4928, 1520-0469 |
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yes |
| Call Number |
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Serial |
7996 |
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| Author |
M. O. Naumenko-Dèzes, Y. Rolland, G. Lamarque, G. Duclaux, S. Gallet, J. Bascou, R. P. Ménot |
| Title |
Petrochronology of the Terre Adélie Craton (East Antarctica) evidences a long-lasting Proterozoic (1.7–1.5 Ga) tectono-metamorphic evolution — Insights for the connections with the Gawler Craton and Laurentia |
Type |
Journal |
| Year |
2020 |
Publication |
Gondwana Research |
Abbreviated Journal |
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| Volume |
81 |
Issue |
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Pages |
21-57 |
| Keywords |
Ar/Ar dating East Antarctica HT metamorphism Mafic magmatism P-T modelling Shear zones |
| Abstract |
The Terre Adélie Craton displays superimposed strain fields related to the Neoarchean (2.6–2.4 Ga, M1) and Paleo-Mesoproterozoic (1.7–1.5 Ga, M2) metamorphic events. M1 is a regional granulite facies event, constrained by P-T modelling at ~0.8–1.0 GPa – 800–850 °C, followed by a decompressional retrogression in the upper amphibolite facies at ~0.6 GPa – 750 °C. M2 Stage 1 P-T peak is constrained at 0.6–0.7 GPa – 670–700 °C, followed by a steep P-T path down to 0.3 GPa – 550 °C. Retrogression after M2 PT peak occurred in a context of dextral shearing along the Mertz Shear Zone along with thrust motions within the eastern Terre Adélie Craton. In this paper, we present a series of 63 new 40Ar/39Ar ages of biotite and amphibole pairs in mafic rocks from a complete traverse of the Terre Adélie Craton. 40Ar/39Ar dating constrains M2 amphibolite facies metamorphism at a regional scale between 1700 and 1650 Ma, during stage 1 peak metamorphism. During retrogression, lower amphibolite facies recrystallization mainly occurred along vertical shear zones and mafic dykes between 1650 and 1600 Ma (Stage 2), followed by amphibolite to greenschist facies metamorphism until after 1500 Ma (Stage 3). At the scale of the Mawson continent, this event is related to the growth of an active margin above an oblique subduction zone. The supra-subduction model best explains opening of Dumont D'Urville and Hunter basins at 1.71 Ga followed by their rapid closure and metamorphism at 1.70 Ga. In this context, episodic shear zone reactivation and magmatic dyke emplacement led to a partial reequilibration of the 40Ar/39Ar system until <1500 Ma. This latter phase of mafic magmatism largely coincides with a hot spot event at the scale of the Gawler Craton and western Laurentia paleocontinent. |
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1003 |
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| ISSN |
1342-937X |
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yes |
| Call Number |
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Serial |
7643 |
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| Author |
Encelyn Voisine, Yann Rolland, Matthias Bernet, Julien Carcaillet, Guillaume Duclaux, Jérôme Bascou, Christian Sue, Mélanie Balvay, René-Pierre Ménot |
| Title |
Antarctic erosion history reconstructed by Terre Adélie moraine geochronology |
Type |
Journal |
| Year |
2020 |
Publication |
Antarctic Science |
Abbreviated Journal |
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| Volume |
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Issue |
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Pages |
1-14 |
| Keywords |
cosmogenic nuclide dating deglaciation exhumation fission-track dating Late Palaeozoic Ice Age subglacial incision |
| Abstract |
We report apatite fission-track and 10Be terrestrial cosmogenic nuclide (TCN) dating of 14 moraine boulders originating from inland Terre Adélie, East Antarctica. These data show cooling of the Proterozoic Terre Adélie craton at < ~120°C between 350 and 300 Ma, suggesting > 4 km temperate glacial erosion during the Late Palaeozoic Ice Age, followed by nearly null Mesozoic erosion and low glacial erosion (< 2 km) in the Cenozoic. Based on glacial flux maps, the origin of the boulders may be located ~400 km upstream. Preliminary TCN (10Be) datings of moraine boulders cluster within the last 30 ka. Cosmogenic ages from the Lacroix Nunatak suggest a main deglaciation after the Younger Dryas at c. 10 ka, while those of Cap Prud'homme mostly cluster at 0.6 ka, in agreement with an exhumation of boulders during the Little Ice Age. |
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1003 |
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| ISSN |
0954-1020, 1365-2079 |
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Approved |
yes |
| Call Number |
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Serial |
7692 |
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| Author |
L. Edel, C. Claud, C. Genthon, C. Palerme, N. Wood, T. L’Ecuyer, D. Bromwich |
| Title |
Arctic Snowfall from CloudSat Observations and Reanalyses |
Type |
Journal |
| Year |
2020 |
Publication |
Journal of Climate |
Abbreviated Journal |
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| Volume |
33 |
Issue |
6 |
Pages |
2093-2109 |
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| Programme |
1013 |
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Thesis |
Bachelor's thesis |
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Edition |
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| ISSN |
0894-8755 |
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| Notes |
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Approved |
yes |
| Call Number |
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Serial |
7657 |
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| Author |
Valentin Wierner |
| Title |
Couverture nuageuse et précipitations neigeuses à Dumont d’Urville |
Type |
Master |
| Year |
2020 |
Publication |
Master's report |
Abbreviated Journal |
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| Volume |
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Issue |
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Pages |
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| Keywords |
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| Abstract |
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| Programme |
1013 |
| Campaign |
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| Address |
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| Corporate Author |
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Thesis |
Bachelor's thesis |
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| Notes |
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Approved |
yes |
| Call Number |
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Serial |
7743 |
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| Author |
Charles Amory |
| Title |
Drifting-snow statistics from multiple-year autonomous measurements in Adélie Land, East Antarctica |
Type |
Journal |
| Year |
2020 |
Publication |
The Cryosphere |
Abbreviated Journal |
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| Volume |
14 |
Issue |
5 |
Pages |
1713-1725 |
| Keywords |
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| Abstract |
Drifting snow is a widespread feature over the Antarctic ice sheet, whose climatological and hydrological significance at the continental scale have been consequently investigated through modelling and satellite approaches. While field measurements are needed to evaluate and interpret model and satellite products, most drifting-snow observation campaigns in Antarctica involved data collected at a single location and over short time periods. With the aim of acquiring new data relevant to the observation and modelling of drifting snow in Antarctic conditions, two remote locations in coastal Adélie Land (East Antarctica) that are 100 km apart were instrumented in January 2010 with meteorological and second-generation IAV Engineering acoustic FlowCapt™ sensors. The data, provided nearly continuously so far, constitute the longest dataset of autonomous near-surface (i.e. within 2 m) measurements of drifting snow currently available over the Antarctic continent. This paper presents an assessment of drifting-snow occurrences and snow mass transport from up to 9 years (2010–2018) of half-hourly observational records collected in one of the Antarctic regions most prone to snow transport by wind. The dataset is freely available to the scientific community and can be used to complement satellite products and evaluate snow-transport models close to the surface and at high temporal frequency. |
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1013 |
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| ISSN |
1994-0416 |
ISBN |
1994-0416 |
Medium |
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| Area |
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Expedition |
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Conference |
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| Notes |
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Approved |
yes |
| Call Number |
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Serial |
8071 |
| Permanent link to this record |
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| Author |
David H. Bromwich, Kirstin Werner, Barbara Casati, Jordan G. Powers, Irina V. Gorodetskaya, François Massonnet, Vito Vitale, Victoria J. Heinrich, Daniela Liggett, Stefanie Arndt, Boris Barja, Eric Bazile, Scott Carpentier, Jorge F. Carrasco, Taejin Choi, Yonghan Choi, Steven R. Colwell, Raul R. Cordero, Massimo Gervasi, Thomas Haiden, Naohiko Hirasawa, Jun Inoue, Thomas Jung, Heike Kalesse, Seong-Joong Kim, Matthew A. Lazzara, Kevin W. Manning, Kimberley Norris, Sang-Jong Park, Phillip Reid, Ignatius Rigor, Penny M. Rowe, Holger Schmithüsen, Patric Seifert, Qizhen Sun, Taneil Uttal, Mario Zannoni, Xun Zou |
| Title |
The Year of Polar Prediction in the Southern Hemisphere (YOPP-SH) |
Type |
Journal |
| Year |
2020 |
Publication |
Bulletin of the american meteorological society |
Abbreviated Journal |
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| Volume |
101 |
Issue |
10 |
Pages |
E1653-E1676 |
| Keywords |
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| Abstract |
Abstract The Year of Polar Prediction in the Southern Hemisphere (YOPP-SH) had a special observing period (SOP) that ran from 16 November 2018 to 15 February 2019, a period chosen to span the austral warm season months of greatest operational activity in the Antarctic. Some 2,200 additional radiosondes were launched during the 3-month SOP, roughly doubling the routine program, and the network of drifting buoys in the Southern Ocean was enhanced. An evaluation of global model forecasts during the SOP and using its data has confirmed that extratropical Southern Hemisphere forecast skill lags behind that in the Northern Hemisphere with the contrast being greatest between the southern and northern polar regions. Reflecting the application of the SOP data, early results from observing system experiments show that the additional radiosondes yield the greatest forecast improvement for deep cyclones near the Antarctic coast. The SOP data have been applied to provide insights on an atmospheric river event during the YOPP-SH SOP that presented a challenging forecast and that impacted southern South America and the Antarctic Peninsula. YOPP-SH data have also been applied in determinations that seasonal predictions by coupled atmosphere–ocean–sea ice models struggle to capture the spatial and temporal characteristics of the Antarctic sea ice minimum. Education, outreach, and communication activities have supported the YOPP-SH SOP efforts. Based on the success of this Antarctic summer YOPP-SH SOP, a winter YOPP-SH SOP is being organized to support explorations of Antarctic atmospheric predictability in the austral cold season when the southern sea ice cover is rapidly expanding. |
| Programme |
1013 |
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| ISSN |
0003-0007, 1520-0477 |
ISBN |
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Approved |
yes |
| Call Number |
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Serial |
8150 |
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| Author |
Amandine Kaiser, Davide Faranda, Sebastian Krumscheid, Danijel Belušić, Nikki Vercauteren |
| Title |
Detecting Regime Transitions of the Nocturnal and Polar Near-Surface Temperature Inversion |
Type |
Journal |
| Year |
2020 |
Publication |
Journal of the atmospheric sciences |
Abbreviated Journal |
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| Volume |
77 |
Issue |
8 |
Pages |
2921-2940 |
| Keywords |
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| Abstract |
Abstract Many natural systems undergo critical transitions, i.e., sudden shifts from one dynamical regime to another. In the climate system, the atmospheric boundary layer can experience sudden transitions between fully turbulent states and quiescent, quasi-laminar states. Such rapid transitions are observed in polar regions or at night when the atmospheric boundary layer is stably stratified, and they have important consequences in the strength of mixing with the higher levels of the atmosphere. To analyze the stable boundary layer, many approaches rely on the identification of regimes that are commonly denoted as weakly and very stable regimes. Detecting transitions between the regimes is crucial for modeling purposes. In this work a combination of methods from dynamical systems and statistical modeling is applied to study these regime transitions and to develop an early warning signal that can be applied to nonstationary field data. The presented metric aims to detect nearing transitions by statistically quantifying the deviation from the dynamics expected when the system is close to a stable equilibrium. An idealized stochastic model of near-surface inversions is used to evaluate the potential of the metric as an indicator of regime transitions. In this stochastic system, small-scale perturbations can be amplified due to the nonlinearity, resulting in transitions between two possible equilibria of the temperature inversion. The simulations show such noise-induced regime transitions, successfully identified by the indicator. The indicator is further applied to time series data from nocturnal and polar meteorological measurements. |
| Programme |
1013 |
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Series Issue |
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Edition |
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| ISSN |
0022-4928, 1520-0469 |
ISBN |
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| Area |
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Expedition |
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Conference |
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| Notes |
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Approved |
yes |
| Call Number |
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Serial |
8151 |
| Permanent link to this record |
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| Author |
Hanane Marif, Jean Lilensten |
| Title |
Suprathermal electron moments in the ionosphere |
Type |
Journal |
| Year |
2020 |
Publication |
Journal of Space Weather and Space Climate |
Abbreviated Journal |
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| Volume |
10 |
Issue |
|
Pages |
22 |
| Keywords |
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| Abstract |
The ionospheric electron population is divided into two groups. The ambient electrons are thermalized. Their energy is usually smaller than one electron volt. Their densities and temperatures are the usual ones measured by incoherent scatter radars, or modeled by international codes such as International Reference Ionosphere (IRI). There is however a second population called the suprathermal electrons. This one is either due to photoionization or to electron impact between the thermosphere and the precipitation in the high latitude zone. In the frame of space weather, it may be the source of scintillations, plasma bulks and other physical phenomena. The suprathermal electron population can only indirectly be measured through the plasmaline and had never been modeled. Its modeling requires the computation of the electron stationary flux by solving the Boltzmann transport equation. This flux is multiplied by various powers of the velocity v and integrated to obtain the different order moments. By integrating f over v0dv, one deduces the suprathermal electron density. An integration of v1fdv allows the computation of their mean velocity. Higher moments give access to their temperature and finally to their heat flux. In this work, we demonstrate for the first time the full and rigorous calculation of the ionospheric electron moments up to three. As two case studies, we focus on high latitude in the auroral oval and low magnetic latitude over Algiers for different solar and geophysical conditions. We compare the suprathermal densities and temperatures to the thermal electron parameters. Our results highlight that – as expected – the suprathermal density is small compared to the thermal one. Although it is close to 3 × 103 m−3 at 180 km during the day, it drops drastically at night, to hardly reach 3 m−3. Contrarily to the density, the velocity is about 10 times more important during the nighttime when precipitation occurs than during the daytime under the electromagnetic solar flux. At 400 km, it varies during the day between 700,000 m s−1 (active solar conditions) and 900,000 m s−1 (quiet Sun). At night, the velocity varies between 3 × 106 m s−1 (low mean energy precipitation) and 3 × 107 m s−1 (high mean energy precipitation) at 400 km. The suprathermal temperature increases as the solar activity decreases or as the mean energy of the electron precipitation increases. It may reach values close to 3 × 108 K. The heat flux may be fully oriented downward or experiences a reversal with some flux going up depending on the forcing. |
| Programme |
1026 |
| Campaign |
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| Address |
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Thesis |
Bachelor's thesis |
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Series Issue |
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Edition |
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| ISSN |
2115-7251 |
ISBN |
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| Area |
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Expedition |
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Conference |
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| Notes |
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Approved |
yes |
| Call Number |
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Serial |
7679 |
| Permanent link to this record |
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| Author |
Léo Bosse, Jean Lilensten, Nicolas Gillet, Sylvain Rochat, Alain Delboulbé, Stephane Curaba, Alain Roux, Yves Magnard, Magnar G. Johnsen, Unni-Pia Løvhaug, Pierre-Olivier Amblard, Nicolas Le Bihan, Maxime Nabon, Hanane Marif, Frédérique Auriol, Camille Noûs |
| Title |
On the nightglow polarisation for space weather exploration |
Type |
Journal |
| Year |
2020 |
Publication |
Journal of Space Weather and Space Climate |
Abbreviated Journal |
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| Volume |
10 |
Issue |
|
Pages |
35 |
| Keywords |
polarisation / aurora |
| Abstract |
We present here observations of the polarisation of four auroral lines in the auroral oval and in the polar cusp using a new ground polarimeter called Petit Cru. Our results confirm the already known polarisation of the red line, and show for the first time that the three other lines observed here (namely 557.7 nm, 391.4 nm and 427.8 nm) are polarised as well up to a few percent. We show that in several circumstances, this polarisation is linked to the local magnetic activity and to the state of the ionosphere through the electron density measured with EISCAT. However, we also show that the contribution of light pollution from nearby cities via scattering can not be ignored and can play an important role in polarisation measurements. This series of observations questions the geophysical origin of the polarisation. It also leaves open its relation to the magnetic field orientation and to the state of both the upper atmosphere and the troposphere. |
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1026 |
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Edition |
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| ISSN |
2115-7251 |
ISBN |
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Expedition |
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Conference |
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| Notes |
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Approved |
yes |
| Call Number |
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Serial |
7796 |
| Permanent link to this record |
