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Atmospheric rivers (ARs) in Antarctica cause strong intrusions of moisture and heat, resulting in intense precipitation events and elevated temperature levels. Here, we examine observed trends in the occurrence of temperature extremes and temperature anomalies at 17 science stations between mid-20th century and 2022 and look at their potential links to ARs. Annual daily maxima of temperature and temperature anomaly are considered extreme if they exceed the 99.7th percentile of the distribution of the variable. Using statistical theory on extreme values, the trend in 10-year return levels of these variables is analyzed. The occurrence of ARs is in turn retrieved using detection algorithms based on meridional integrated vapor transport (vIVT) and integrated water vapor (IWV) calculations. The results show a significant increase (p < 0.1) in the 10-year return levels of extreme temperatures for three stations on the Antarctic Peninsula, one in the eastern Weddell Sea region and two on the East Antarctic shelf. At the same time, over the East Antarctic Ice Sheet, a significant (p < 0.1) decrease in decadal return levels is observed at four stations. The relationship between these extremes and atmospheric rivers depends on the detection scheme used, but the results indicate that 7-54% of temperature extremes are associated with ARs, while 19-75% of extreme anomalies are associated with ARs. A strong increase in the frequency of atmospheric rivers is observed in the Antarctic Peninsula, which could explain the increase in temperature extremes in this region., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

This study explores the grain size seasonal variations on the East Antarctic Plateau, where dry metamorphism occurs, by using microwave radiometer observations from 2000 to 2022. Local meteorological conditions and large scale atmospheric phenomena have been considered in order to explain some peculiar changes of the snow grains. We find that the highest ice divide is the region with the largest grain size in the summer, mainly because the wind speed is low. Moreover, some extreme grain size values with respect to the average (over +3σ) were identified. In these cases, the ERA5 reanalysis revealed a high pressure blocking/ridge situation in the proximity of the onsets of the summer increase of the grain size, conveying the relatively warm and moist air coming from the mid latitudes, often associated with atmospheric rivers. If weak wind and low temperature conditions occur during the following weeks, dry snow metamorphism is facilitated, leading to grain growth. This determines anomalous high maximums of the snow grain size at the end of summer. These phenomena confirm the importance of moisture intrusion events in the East Antarctica and their impact on the physical properties of the ice sheet surface, with a co-occurrence of atmospheric rivers and seasonal changes of the grain size significant over 95 %.

Point d’étape sur le bouleversement en cours et la forme qu’il revêt..

Biodiversité, rendements agricoles, élevage, pêche… Rien n’est épargné par le changement climatique. Zoom sur deux effets en passe de devenir tristement familiers.

The West African Monsoon (WAM) brings precipitation in summer for around 80 million people from Senegal to Chad. Variability of the monsoon circulation has large impacts on Sahelian societies. However, future changes in Sahel precipitation are uncertain because of large differences between projections of various climate models. We show that uncertainty in Sahel precipitation change is associated with uncertainty at simulating future changes in surface air temperature over the northern Hemisphere, towards the end of the 21st century. We use a storyline approach, a statistical method, to construct scenarios of changes in Sahel precipitation, whose differences only depend on effects and uncertainty at simulating selected remote drivers of Sahel precipitation change. We select two remote drivers, the warming of the Atlantic Ocean and of the Euro-Mediterranean area. We show that uncertainty in changes in Atlantic Ocean and Euro-Mediterranean surface air temperature explains up to 50% of Sahel precipitation change uncertainty. We suggest that reducing uncertainty in the future warming of the North Atlantic and the Euro-Mediterranean areas would then allow reducing uncertainty in future changes in Sahel precipitation., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

International audience; La modélisation atmosphérique à très fine échelle permet d’analyser la dynamique de l’îlot dechaleur urbain en contexte de topographie complexe. Deux simulations (Urbaine et Non-Urbaine) mettenten évidence les effets associés à l'urbanisation. La taille des agglomérations, dans le cas de Lyon etGrenoble, n'influence pas la différence de température entre les deux simulations. Les conditions destabilité influencent fortement ces différences. L'ICU peut être intensifié par l'affaiblissement du vent oul’effet de piégeage et/ou le développement d’une couche d’inversion.

This article offers some theoretical considerations on the literacy of Robert of Torigni (1106-1186), monk/prior of Le Bec (dép. Eure, cant. Brionne) and abbot of Mont-Saint-Michel (dép. Manche, cant. Pontorson), and one of the most celebrated historians of the twelfth century. In recent years, scholars have shown a renewed interest in Robert as an author and scribe, including his handwriting, his librarianship, his use of archival sources, and his working methods as a historian. At the same time, however, there is no study that approaches Robert’s relationship with the written word from a conceptual point of view. The present article attempts to fill this lacuna by revisiting Robert’s literary activities in the light of what is known amongst medievalists as the concept of “pragmatic literacy”. Cet article offre quelques réflexions théoriques autour de l’écriture de Robert de Torigni (1106-1186), moine / prieur du Bec-Hellouin (dép. Eure, cant. Brionne), abbé du Mont-Saint-Michel (dép. Manche, cant. Pontorson) et célèbre historien du XIIe siècle. Ces dernières années, les chercheurs se sont intéressés à Robert en tant qu’auteur et scribe en se penchant notamment sur son écriture, sa bibliothéconomie, son utilisation des archives et ses méthodes de travail. Cependant, aucune étude n’aborde la relation de Robert avec l’écrit d’un point de vue conceptuel. Cet article se propose donc de combler ces lacunes en réexaminant les activités littéraires de Robert à la lumière du concept d’« écriture pragmatique » bien connu des médiévistes. Questo articolo offre alcune riflessioni teoriche sulla scrittura di Roberto di Torigni (1106-1186), monaco/priore di Bec-Hellouin (Eure, Brionne), abate di Mont-Saint-Michel (Manche, Pontorson) e famoso storico del XII secolo. Negli ultimi anni, i ricercatori si sono interessati a Robert come autore e scriba, concentrandosi in particolare sulla sua scrittura, la sua biblioteconomia, il suo uso degli archivi e i suoi metodi di lavoro. Tuttavia, nessuno studio ha affrontato il rapporto di Robert con la parola scritta da un punto di vista concettuale. Questo articolo si propone quindi di colmare questa lacuna riesaminando le attività letterarie di Robert alla luce del concetto di “scrittura pragmatica” ben noto ai medievalisti. Dieser Aufsatz bietet einige theoretisch-methodische Erwägungen zum Schriftverständnis und zum Schriftgebrauch Roberts von Torigni (1106-1186), des Mönchs und Kloster-Priors von Le Bec (dép. Eure, cant. Brionne) und späteren Abts von Mont-Saint-Michel (dép. Manche, cant. Pontorson), der zu den bekanntesten Geschichtsschreibern des zwölften Jahrhunderts zählt. Jüngere Forschungen haben erneut Interesse an Robert gezeigt, insbesondere an seinen Funktionen als Autor, Schreiber/Kalligraph, Bibliothekar und Benutzer archivalischer Schriften, sowie an seinen Arbeitsmethoden als Historiker. Eine konzeptuelle Untersuchung zu Roberts Beziehung mit unterschiedlichen Gebrauchs- und Ausdrucksformen mittelalterlicher Schriftlichkeit ist hingegen bislang nicht versucht worden. Der vorliegende Aufsatz widmet sich diesem Desiderat, indem er Roberts Schrifttätigkeit erstmals konkret im Rahmen „pragmatischer Schriftlichkeit“ durchleuchtet.