Linking Ocean Variabilty to Phytoplankton Changes Over the Last 2000 Years off N. Iceland

• Main Authors: Bouloubassi, Ioanna, Sicre, Marie-Alexandrine, Ezat, Ullah, Gondry, Geneviève, Jacob, Jérémy, Azzoug, Moufok
• Other Authors: Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institut des Sciences de la Terre d'Orléans (ISTO), Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2008
• Subjects: [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDE.MCG]Environmental Sciences/Global Changes; Arctic Ocean; East Greenland; Greenland; Iceland; North Atlantic; North Atlantic oscillation; Phytoplankton; Sea ice
• Online Access: https://insu.hal.science/insu-00442934

International audience Understanding ocean variability at decadal to century time-scale is a key issue of climate research, yet it remains poorly described partly because high resolution marine records are lacking. Recent observations also suggested that climate-driven oceanic changes may also affect marine productivity reflecting adjustments of the pelagic ecosystem. To explore these issues we investigated sediment cores (a Calypso and a box core) off North Iceland at unprecedented high temporal resolution (2 to 5 years). The area lies in a sensitive boundary region with strong climatic gradients between the Arctic and the North Atlantic realms. Surface hydrology is affected by warm, high salinity Atlantic water (Irminger current-IC) and cold, low salinity water of the East Icelandic Current (EIC), as well as by sea ice and drifting ice exported from the Arctic Ocean and East Greenland. Using biomarker proxies we reconstructed, over the past two millennia, high frequency surface ocean properties, such as Sea Surface Temperature (SST) and patterns of major phytoplankton groups. Records from a box core covering the last 80 years and comparison with instrumental data allowed to improve constrain of the proxies used. The SST curve reveals 4 major oscillations of about 20-25 years, depicting also the Great Salinity Anomaly (GSA). It reflects ocean circulation changes with varying impact of Polar and Atlantic waters (EIC, IC). Similarities with the NAO (North Atlantic Oscillation) index suggest links between STT and westerlies intensity. Phytoplankton biomarker profiles (specific phytosterols and alkenones) are consistent with biological data acquired during annual surveys. They show significant increase in periods when Atlantic waters and subsequent mixing processes prevail during positive NAO phase, compared to low levels when Polar waters and stratified conditions occur. Over the last two millennia the SST curve depicts a broad cooling trend towards present, steepening over the last 500 years. Prolonged warm or ...