Reconstruction of extreme climatic events (floods and storms) during the Holocene in the Gulf of Aigues-Mortes (southern France)

• Main Author: Sabatier, Pierre
• Other Authors: Géosciences Montpellier, Université des Antilles et de la Guyane (UAG)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Université de Montpellier 2, Laurent Dezileau, Michel Condomines
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2009
• Subjects: radiocarbon; paleostrom; lagoon; Mediterranean climate; paléotempêtes; lagune; Climat Méditerranéen; radiocarbone; Holocène; [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Tempêtes; North Atlantic
• Online Access: https://theses.hal.science/tel-00437757; https://theses.hal.science/tel-00437757/document; https://theses.hal.science/tel-00437757/file/Sabatier_these.pdf

The effects of climate change on extreme events are difficult to assess because extremes present large variability and consequently, it is difficult to identify significant trends in relation to the lack of instrumental long time series. Here we present a record of these extreme storm events in the French Mediterrannean coast over the past 7000 years based on a long sediment core from lagoonal environment in Gulf of Lions. Using a high resolution multiproxies approach on core associating grain size, faunal to reconstruct Mid to Late Holocene history of backbarrier deposits in relation to landfalling activity. Even if change in lagoon geomorphological setting over the Holocene does not allow to compare storm events in terms of intensity trough time, we have recorded six periods of increase in storm activity at 6200, 5500, 4400, 3200, 1500 yr cal B.P. and over the LIA (450 and 100 yr cal B.P.). These evidences of changes in coastal hydrodynamic, inversely correlated to periods of aridification in Western Mediterranean region, are in phase with those observed over the North Atlantic and correspond to Holocene cooling events. This increase in storm activity during Holocene cold events over Mediterranean region was probably due to thermal gradient increase leading to enhanced lower tropospheric baroclinicity over a large Central Atlantic-European domain. This study demonstrates that temperatures in North Atlantic region influence the severe storm activity and therefore the Mediterranean climate at Holocene timescale. Les effets du changement climatique sur les événements extrêmes sont difficiles à estimer car ces phénomènes présentent une large variabilité, et par conséquent il est délicat d'identifier des tendances significatives compte tenu de l'absence de longues séries de données instrumentales. Dans cette étude, nous présentons un enregistrement de ces tempêtes extrêmes sur la côte Méditerranéenne française au cours des 7000 dernières années à partir de carottes sédimentaires prélevées dans un système ...