Saisonalität und zwischenjährliche Klimavariabilität in der Karibik während des letzten Interglazials rekonstruiert anhand von Korallenzeitreihen
Zusammenfassung der Projektergebnisse
Reconstructions of the last interglacial climate (~127-117 ka ago) offer insights into the natural response of the climate system and its variability during a period partially analogous to future climate change scenarios. Here we present well preserved fossil brain corals (Diploria strigosa) recovered from an elevated reef terrace at the southern Caribbean island of Bonaire (Caribbean Netherlands) in the tropical North Atlantic Ocean that have been precisely dated by the 230Th/U-method to between 130 and 118 ka ago. Annual banding of the coral skeleton enabled construction of time windows of monthly resolved strontium/calcium (Sr/Ca) temperature proxy records. Our eight coral records of up to 37 years in length cover a total of 105 years within the last interglacial period. From these coral Sr/Ca records sea surface temperature (SST) seasonality and variability in the tropical North Atlantic Ocean is reconstructed. In particular, for the first time, tropical SST seasonality is reconstructed and quantified for different time windows of an interglacial at a single site, reflecting periods of different orbital insolation forcing. We detect similar to modern SST seasonality of ~2.9 °C during the early (130 ka ago) and the late last interglacial (120-118 ka ago). Within the mid last interglacial, a significantly higher than modern SST seasonality of 4.9 °C (at 126 ka ago) and 4.1 °C (at 124 ka ago) is observed. These findings are supported by our simulations performed with a coupled atmosphereocean general circulation model (COSMOS) and are consistent with the evolving amplitude of orbitally induced changes in seasonality of insolation throughout the last interglacial, irrespective of wider oceanic and climatic instabilities that characterized this period. The climate model simulations suggest that the SST seasonality changes documented in our last interglacial coral Sr/Ca records are representative of larger regions within the tropical North Atlantic Ocean. These simulations also suggest that the reconstructed SST seasonality increase during the mid last interglacial is caused primarily by summer warming. Moreover, a 124 ka coral documents, for the first time, evidence for decadal SST variability in the tropical North Atlantic during the last interglacial, akin to that observed in modern instrumental records. Our coral records and climate model simulations indicate an orbital control on temperature seasonality in the tropical North Atlantic throughout the last interglacial, despite large-scale perturbations of ocean circulation and climate that occurred during this period. Our findings suggest that temperature seasonality of the tropical surface ocean is controlled mainly by orbital insolation changes during interglacials. Press release (22 January 2015) MARUM, University of Bremen: Klimalehren aus der Vergangenheit - Neue Korallenstudie in Nature Communications (Climate lessons from the past - New coral study in Nature Communications) Informationsdienst Wissenschaft (idw) [https://idw-online.de/de/news621388] Online article (2 February 2015) “Bonaire Insider”: Lessons from the Last Interglacial - Bonaire plays an integral part in new coral study [http://www.bonaireinsider.com/index.php/bonaireinsider/lessons_from_the_last_inter glacial_new_coral_study_in_nature_communications/] Newspaper article (2 February 2015) „Kreiszeitung“ (Bremen area): Klimaschnappschuss aus der Vergangenheit (Climate snapshot from the past)
Projektbezogene Publikationen (Auswahl)
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(2015) Tropical Atlantic temperature seasonality at the end of the last interglacial. Nature Communications, 6, 6159
Felis, T., Giry, C., Scholz, D., Lohmann, G., Pfeiffer, M., Pätzold, J., Kölling, M. and Scheffers, S. R.
