Browsing by Author "Rossignol, L."
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- Assessment of sea surface temperature changes in the Gulf of Cadiz during the last 30 ka: Implications for glacial changes in the regional hydrographyPublication . Penaud, A.; Eynaud, F.; Voelker, Antje; Kageyama, M.; Marret, F.; Turon, J.L.; Blamart, D.; Mulder, T.; Rossignol, L.New dinocyst analyses were conducted on core MD99-2339 retrieved from the central Gulf of Cadiz. Dinocyst and foraminiferal assemblages from this core are combined with existing data off SW Portugal and NW Morocco to investigate past hydrological and primary productivity regimes in the subtropical NE Atlantic Ocean over the last 30 ka. Our results have revealed highest upwelling intensity during Heinrich Stadial 1 (HS 1) and the Younger Dryas and weaker upwelling cells during the Last Glacial Maximum (LGM) and HS 2, off the SW Iberian and NW Moroccan margins. Similar assemblages between the Gulf of Cadiz and the NW Moroccan margin, and distinct species off Portugal, were observed during the cold climatic extremes that punctuated the last 30 ka. This pattern has been linked to the occurrence of a hydrological structure between SW Iberia and Cadiz during the last glacial period, perhaps similar to the modern Azores Front. This front was probably responsible locally for heterotrophic dinocysts found in the Gulf of Cadiz during the last glacial period, even if this sector is not conductive to upwelling phenomena by Ekman transport. Regional reconstructions of paleo-sea-surface temperatures (SSTs) using dinocyst and foraminiferal transfer functions, as well as alkenones, are also discussed and depict coherent scenarios over the last 30 ka. Seasonal reconstructions Correspondence to: A. Penaud (aurelie.penaud@univ-brest.fr.) of LGM SSTs obtained with this multi-proxy panel are discussed jointly with model outputs in order to contribute to ongoing efforts in model-data comparison
- Climate variability across the last deglaciation in NW Iberia and its marginPublication . Naughton, F.; Goni, Maria F. Sanchez; Rodrigues, T.; Salgueiro, Emilia; Costas, Susana; Desprat, S.; Duprat, J.; Michel, E.; Rossignol, L.; Zaragosi, S.; Voelker, Antje; Abrantes, FatimaThe direct comparison between marine and terrestrial data from the NW Iberian margin, core MD03-2697, allows us to accurately evaluate, without chronological ambiguity, the vegetation response to North Atlantic climate events across the last deglaciation. Comparison of MD03-2697 data with other marine and terrestrial records from a vast area stretching from the Azores to western (W) France, Iberia and its margin, the W Mediterranean and NW Africa reveals the importance of enhanced winter North Atlantic westerlies episodes in driving a heterogeneous regional climatic signal during particular events of the last deglaciation. Heinrich Stadial 1 (HS1)/Oldest Dryas is a complex event marked by three synchronous main phases (a: extremely cold/relatively wet; b: cool/dry; c: relatively warmer/increasing moisture availability) in regions directly influenced by the North Atlantic while it is characterized by a single phase (cold and dry) in most inland and high altitude areas. Changes in the strength and position of North Atlantic westerlies could explain the variability in moisture during HS1 from W Pyrenees to W Mediterranean. The Bolling-Allerod (B-A) event is marked by a synchronous progressive increase of ocean and atmospheric temperatures and precipitation from the Bolling to the Allerod in W Iberia and W Pyrenees contrasting with the Greenland temperature pattern. Mid-to high latitudes thermal contrast and the gradual strengthening of the Atlantic Meridional Overturning Circulation (AMOC) triggered the continuing enhancement of westerlies, and moisture, along this period.Finally, the Younger Dryas (YD) Stadial is characterized by a land-ocean synchronous returning cold conditions (but not so cold as HS1) and, although dry conditions persisted during this period, extreme winter precipitation occurrences might have affected the most coastal areas of north and central W Iberia and Pyrenees. In contrast, dry conditions persisted during the YD in the western Mediterranean regions. The westerlies migrated further north following the displacement of the Polar Front during the deglaciation precluding the input of moisture in the W Mediterranean region, which persisted very dry during the YD Stadial. (C) 2016 Published by Elsevier Ltd.