Late Holocene surface water changes in the eastern Nordic Seas : the message from carbonate and organic-walled phytoplankton microfossils

• Main Author: Dylmer, Christian
• Other Authors: Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux I, Jacques Giraudeau
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2013
• Subjects: Eastern Nordic Seas; Late Holocene; Atlantic water flow; Surface waters; Coccoliths; Dinocysts; Mers Nordiques; Holocène terminal; Flux d’eaux atlantiques; Eaux de surface; Coccolithes; Dinokystes; [SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology; Arctic; Svalbard; Barents Sea; Norway; Fram Strait; Nordic Seas; North Atlantic; North Atlantic oscillation; Phytoplankton; Sea ice; Spitsbergen
• Online Access: https://theses.hal.science/tel-00959281; https://theses.hal.science/tel-00959281/document; https://theses.hal.science/tel-00959281/file/DYLMER_CHRISTIAN_2013.pdf

Five marine sediment cores distributed along the Norwegian, western Barents Sea, and Svalbard continental margins have been investigated in order to reconstruct late Holocene changes in the poleward flow of the Norwegian Atlantic Current (NwAC) and West Spitsbergen Current (WSC) and the nature of the upper surface water masses within the eastern Nordic Seas. This research project is based on the use of dinocyst and coccolith assemblages for qualitative and quantitative reconstructions of surface water conditions from high resolution sediment cores, and involve upstream investigations on proxy reliabilities. The investigated area (66 to 77°N) was affected by an overall increase in the strength of the AW flow from 3000 cal. yrs BP to the Present. The long-term modulation of westerlies strength and location which are essentially driven by the dominant mode of the North Atlantic Oscillation (NAO), is thought to explain the observed dynamics of the AW flow. The same mechanism also reconciles the recorded opposite zonal shifts in the location of the Arctic Front between the area off western Norway and the western Barents Sea-eastern Fram Strait region. Submillenial changes in AW flow are organised according to known pre-Anthropocene warm (RWP, MCA and the Modern period: strong poleward flow) and cold (LIA, DA: weak poleward flow) climatic spells. A sudden short pulse of resumed high WSC flow interrupted the LIA in the eastern Nordic Seas from 330 to 410 cal. yrs BP. Our results are indicative of a major impact of AW flow dynamics on the Arctic sea ice distribution during the last millenium, when changes in reconstructed sea-ice extent are negatively correlated with the strength of the WSC flow off western Barents Sea and western Svalbard. The extensive decrease in sea ice extent during the last century is synchronous with an exceptional increase in AW flow. The previously reconstructed high amplitude warming of surface waters in eastern Fram Strait at the turn of the 19th century was therefore primarily induced by an ...