Antarctique | EPFL Graph Search

L'Antarctique (prononcé , ou aussi ), parfois appelé « le Continent Austral » ou « le Continent Blanc », est le continent le plus méridional de la Terre. Situé autour du pôle Sud, il est entouré des mers de Ross et de Weddell et, suivant les classifications, des océans Atlantique, Indien et Pacifique ou du seul océan Austral. Il forme le cœur de la région antarctique qui inclut également les parties émergées du plateau des Kerguelen ainsi que d'autres territoires insulaires de la plaque antarctique plus ou moins proches. L'ensemble de ces territoires, qui partagent des caractéristiques écologiques communes, constitue l'écozone antarctique. Avec une superficie de de kilomètres carrés, l'Antarctique est plus petit que l'Asie, l'Afrique ou l'Amérique ; seules l'Europe et l'Océanie sont plus petites que lui. Quelque 98 % de sa surface sont recouverts d'une couche de glace d'une épaisseur moyenne de . C'est pourquoi la morphologie du sous-sol antarctique reste encore peu connue voire i

Synoptic moisture pathways associated to virga and precipitation over coastal Adélie Land.

Nicolas Jean François Jullien

The Antarctic ice sheet store large amount of water under solid form over the continent. As climate change is going on, this reservoir already started to contribute to global sea level rise, and will contribute more in the future. With precipitation being the main input to the ice sheet, it is essential to understand the synoptic conditions determining moisture pathways that are being transported towards Antarctica. Because of katabatic flow, it was evidenced that coastal regions experiences low-level sublimation, reducing the amount of precipitation reaching the ground. This issue is not well represented in models, which can lead to wrong estimations of the surface mass balance. Using ground-based radar measurements deployed during the APRES3 campaign and the outcomes of the atmospheric reanalysis model LAGRANTO, it was possible to identify, and characterize the main synoptic conditions associated to virga and precipitation event at Dumont d’Urville station, Adélie Land, coastal Antarctica. It was found that precipitation there are associated to warm front, and that virga events proceed and succeed precipitation events. On their way to precipitate above Dumont d’Urville, virga experience a lifting much earlier in time, compared to precipitation. The trajectories, as well as localization of maximum lifting and moisture source of the air parcels show differences between virga, and precipitation events.

2019

A fascinating trip to Antarctica

Armin Sigmund

Researchers from EPFL have been joining the Belgian Antarctic Research Expedition to Princess Elisabeth Antarctica Station every year since 2016. Armin Sigmund, a PhD student in the Laboratory of Cryospheric Sciences, recently participated in the expedition to study snow-atmosphere interactions. After coming back from the extreme and impressive environments of Antarctica, he provided insights into his first trip to the polar regions.

2021

Synoptic conditions and atmospheric moisture pathways associated with virga and precipitation over coastal Adelie Land in Antarctica

Alexis Berne, Nicolas Jean François Jullien, Etienne Gabriel Henri Vignon

Precipitation falling over the coastal regions of Antarctica often experiences low-level sublimation within the dry katabatic layer. The amount of water that reaches the ground surface is thereby considerably reduced. This paper investigates the synoptic conditions and the atmospheric transport pathways of moisture that lead to either virga - when precipitation is completely sublimated - or actual surface precipitation events over coastal Adelie Land, East Antarctica. For this purpose, the study combines ground-based lidar and radar measurements at Dumont d'Urville station (DDU), Lagrangian back trajectories, Eulerian diagnostics of extratropical cyclones and fronts, and moisture source estimations. It is found that precipitating systems at DDU are associated with warm fronts of cyclones that are located to the west of Adelie Land. Virga - corresponding to 36% of the hours with precipitation above DDU - and surface precipitation cases are associated with the same precipitating system but they correspond to different phases of the event. Virga cases more often precede surface precipitation. They sometimes follow surface precipitation in the warm sector of the cyclone's frontal system, when the associated cyclone has moved to the east of Adelie Land and the precipitation intensity has weakened. On their way to DDU, the air parcels that ultimately precipitate above the station experience a large-scale lifting across the warm front. The lifting generally occurs earlier in time and farther from the station for virga than for precipitation. It is further shown that the water contained in the snow falling above DDU during pre-precipitation virga has an oceanic origin farther away (about 30 degrees more to the west) from Adelie Land than the one contained in the snow that precipitates down to the ground surface.

2020

Synoptic conditions and atmospheric moisture pathways associated with virga and precipitation over coastal Adelie Land in Antarctica

Alexis Berne, Nicolas Jean François Jullien, Etienne Gabriel Henri Vignon

2020