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      Millennial‐Scale Climate Variability and Dinoflagellate‐Cyst‐Based Seasonality Changes Over the Last ~150 kyrs at “Shackleton Site” U1385

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          Abstract

          During the last glacial period, climate conditions in the North Atlantic region were determined by the alternation of relatively warm interstadials and relatively cool stadials, with superimposed rapid warming (Dansgaard‐Oeschger) and cooling (Heinrich) events. So far little is known about the impact of these rapid climate shifts on the seasonal variations in sea surface temperature (SST) within the North Atlantic region. Here, we present a high‐resolution seasonal SST record for the past 152 kyrs derived from Integrated Ocean Drilling Program “Shackleton” Site U1385, offshore Portugal. Assemblage counts of dinoflagellates cysts (dinocysts) in combination with a modern analog technique (MAT), and regression analyses were used for the reconstructions. We compare our records with previously published SST records from the same location obtained from the application of MAT on planktonic foraminifera. Our dinocyst‐based reconstructions confirm the impression of the Greenland stadials and interstadials offshore the Portuguese margin and indicate increased seasonal contrast of temperature during the cold periods of the glacial cycle (average 9.0 °C, maximum 12.2 °C) with respect to present day (5.1 °C), due to strong winter cooling by up to 8.3 °C. Our seasonal temperature reconstructions are in line with previously published data, which showed increased seasonality due to strong winter cooling during the Younger Dryas and the Last Glacial Maximum over the European continent and North Atlantic region. In addition, we show that over longer time scales, increased seasonal contrasts of temperature remained characteristic of the colder phases of the glacial cycle.

          Key Points

          • New high‐resolution dinocyst‐based summer and winter SST record from IODP “Shackleton” Site U1385 for the last 150 kyrs is presented

          • Dinocyst‐based SST confirms the D‐O cycles and HEs at Site U1385

          • Increased seasonal contrast of SST (up to 12 degree C) during cold periods of the glacial cycle related to strong winter cooling is shown

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          Most cited references108

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          Sea-surface temperature from coral skeletal strontium/calcium ratios.

          Seasonal records of tropical sea-surface temperature (SST) over the past 10(5) years can be recovered from high-precision measurements of coral strontium/calcium ratios with the use of thermal ionization mass spectrometry. The temperature dependence of these ratios was calibrated with corals collected at SST recording stations and by (18)O/(16)O thermometry. The results suggest that mean monthly SST may be determined with an apparent accuracy of better than 0.5 degrees C. Measurements on a fossil coral indicate that 10,200 years ago mean annual SSTs near Vanuatu in the southwestern Pacific Ocean were about 5 degrees C colder than today and that seasonal variations in SST were larger. These data suggest that tropical climate zones were compressed toward the equator during deglaciation.
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              Four climate cycles of recurring deep and surface water destabilizations on the Iberian margin.

              Centennial climate variability over the last ice age exhibits clear bipolar behavior. High-resolution analyses of marine sediment cores from the Iberian margin trace a number of associated changes simultaneously. Proxies of sea surface temperature and water mass distribution, as well as relative biomarker content, demonstrate that this typical north-south coupling was pervasive for the cold phases of climate during the past 420,000 years. Cold episodes after relatively warm and largely ice-free periods occurred when the predominance of deep water formation changed from northern to southern sources. These results reinforce the connection between rapid climate changes at Mediterranean latitudes and century-to-millennial variability in northern and southern polar regions.
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                Author and article information

                Contributors
                m.c.datema@uu.nl
                Journal
                Paleoceanogr Paleoclimatol
                Paleoceanogr Paleoclimatol
                10.1002/(ISSN)2572-4525
                PALO
                Paleoceanography and Paleoclimatology
                John Wiley and Sons Inc. (Hoboken )
                2572-4517
                2572-4525
                16 July 2019
                July 2019
                : 34
                : 7 ( doiID: 10.1002/palo.v34.7 )
                : 1139-1156
                Affiliations
                [ 1 ] Marine Palynology and Paleoceanography, Laboratory of Palaeobotany and Palynology, Department of Earth Sciences, Faculty of Geosciences Utrecht University Utrecht The Netherlands
                [ 2 ] Centre de recherche en géochimie et géodynamique (Geotop) Université du Québec à Montréal Montréal Quebec Canada
                [ 3 ] Department of Earth Sciences, Faculty of Geosciences Utrecht University Utrecht The Netherlands
                [ 4 ] Department of Ocean Systems NIOZ Royal Netherlands Institute for Sea Research Texel The Netherlands
                Author notes
                [*] [* ] Correspondence to: M. Datema,

                m.c.datema@ 123456uu.nl

                Author information
                https://orcid.org/0000-0001-5963-3935
                https://orcid.org/0000-0001-5656-724X
                https://orcid.org/0000-0002-7256-2243
                https://orcid.org/0000-0002-3815-7770
                https://orcid.org/0000-0003-2382-0215
                Article
                PALO20743 2018PA003497
                10.1029/2018PA003497
                6774308
                173ae7a3-1875-43f8-943b-87671f80d0b7
                ©2019. The Authors.

                This is an open access article under the terms of the http://creativecommons.org/licenses/by-nc-nd/4.0/ License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.

                History
                : 19 October 2018
                : 03 May 2019
                : 15 May 2019
                Page count
                Figures: 4, Tables: 0, Pages: 18, Words: 8870
                Funding
                Funded by: EC | FP7 | FP7 Ideas: European Research Council (FP7 Ideas)
                Award ID: 259627
                Funded by: European Research Council (ERC)
                Award ID: 259627
                Categories
                Biogeosciences
                Paleoclimatology and Paleoceanography
                Atmospheric Processes
                Paleoclimatology
                Paleoceanography
                Research Article
                Research Articles
                Custom metadata
                2.0
                palo20743
                July 2019
                Converter:WILEY_ML3GV2_TO_NLMPMC version:5.6.9 mode:remove_FC converted:01.10.2019

                seasonality,sea surface temperature (sst) dinocysts,shackleton site u1385

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