Mainz Academy of science

Mainz, Germany

Mainz Academy of science

Mainz, Germany
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Kandiano E.S.,Leibniz Institute of Marine Science | Bauch H.A.,Leibniz Institute of Marine Science | Bauch H.A.,Mainz Academy of science | Fahl K.,Alfred Wegener Institute for Polar and Marine Research | And 4 more authors.
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2012

Temporal and spatial patterns in eastern North Atlantic sea-surface temperatures (SST) were reconstructed for marine isotope stage (MIS) 11c using a submeridional transect of five sediment cores. The SST reconstructions are based on planktic foraminiferal abundances and alkenone indices, and are supported by benthic and planktic stable isotope measurements, as well as by ice-rafted debris content in polar and middle latitudes. Additionally, the larger-scale dynamics of the precipitation regime over northern Africa and the western Mediterranean region was evaluated from iron concentrations in marine sediments off NW Africa and planktic δ 13C in combination with analysis of planktic foraminiferal abundances down to the species level in the Mediterranean Sea. Compared to the modern situation, it is revealed that during entire MIS 11c sensu stricto (ss), i.e., between 420 and 398ka according to our age models, a cold SST anomaly in the Nordic seas co-existed with a warm SST anomaly in the middle latitudes and the subtropics, resulting in steeper meridional SST gradients than during the Holocene. Such a SST pattern correlates well with a prevalence of a negative mode of the modern North Atlantic Oscillation. We suggest that our scenario might partly explain the longer duration of wet conditions in the northern Africa during MIS 11c compared to the Holocene. © 2012 Elsevier B.V.

Van Nieuwenhove N.,Leibniz Institute of Marine Science | Bauch H.A.,Leibniz Institute of Marine Science | Bauch H.A.,Mainz Academy of science | Eynaud F.,University of Bordeaux 1 | And 3 more authors.
Quaternary Science Reviews | Year: 2011

The Last Interglacial (Marine Isotopic Stage or MIS 5e) surface ocean heat flux from the Rockall Basin (NE Atlantic) towards the Arctic Ocean was reconstructed by analysing dinoflagellate cyst (dinocyst) assemblages in four sediment cores. Together with records of stable isotopes and ice-rafted detritus, the assemblage data reflect the northward retreat of ice(berg)-laden waters and the gradual development towards interglacial conditions at the transition from the Saalian deglaciation (Termination II) into MIS 5e. At the Rockall Basin, this onset of the Last Interglacial is soon followed by the appearance of the thermophilic dinocyst species Spiniferites mirabilis, with relative abundances higher than those observed at present in the area. North of the Iceland-Scotland Ridge, however, S. mirabilis only appears in significant numbers during late MIS 5e, between ∼118 and 116.5 ka. Hence, fully marine Last Interglacial conditions with most intense Atlantic surface water influence occurred during late MIS 5e in the Nordic seas, and consequently also farther north in the Arctic Ocean, and at times when northern hemisphere summer insolation was already significantly decreased. The stratigraphic position of this Late Interglacial optimum is supported by planktic foraminifers and contrasts with the timing of the early Holocene climatic optimum in this area. We interpret the delayed northward expansion of Atlantic waters towards the polar latitudes as a result of the Saalian ice sheet deglaciation and its specific impact on the subsequent water mass evolution in this region. © 2011 Elsevier Ltd.

Bashirova L.D.,Immanuel Kant Baltic Federal University | Kandiano E.S.,University of Kiel | Sivkov V.V.,Immanuel Kant Baltic Federal University | Bauch H.A.,Mainz Academy of science
Oceanology | Year: 2014

The main migrations of the Polar front (PF) during the last 300 ka were identified using planktic foraminiferal census data and derived from them sea surface paleotemperature (SST) estimates in two synchronized AMK-4438 and M23414 cores recovered directly beneath the main stream of the North Atlantic Current (NAC) south of Iceland. During the summer seasons, the cold waters adjacent to the PF did not reach the studied sites. These waters occurred here only during the winter seasons of MIS 2, 6, and 8. The northern part of the study area was influenced by the arctic waters more often than its southern part. During MIS 8 and 6 isotherms in the North Atlantic had mainly the subzonal orientation, while during MIS 2–4 they had the submeridional orientation. During the interglacials, the PF was located northward and westward from the study area. During MIS 7, the front was presumably situated closer to the study area in comparison with its modern position, and the isotherms were oriented mainly subzonal. For the MIS 5e period, we observed the most distant retreat of PF from the investigated area in the western and northwestern direction in relation to the anomalous deflection of the NAC to the north-west (intensification of the Irminger current) and the predominance of the submeridional orientation of the isotherms in the study area. During MIS 1, as well as MIS 7, the isotherms in the study area had mainly the subzonal orientation. © 2014, Pleiades Publishing, Inc.

Van Nieuwenhove N.,Leibniz Institute of Marine Science | Van Nieuwenhove N.,University of Quebec at Montréal | Bauch H.A.,Leibniz Institute of Marine Science | Bauch H.A.,Mainz Academy of science | Andruleit H.,Bundesanstalt fur Geowissenschaften und Rohstoffe
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2013

Dinoflagellate cyst (dinocyst), coccolith and planktic foraminiferal assemblages from a core in the western Iceland Sea were used to reconstruct and compare the surface ocean developments of the Holocene and the Last Interglacial (Marine Isotopic Stage or MIS 5e). While increasing subpolar planktic foraminifers from ~. 10. ka indicate subsurface warming peaking around 7.5. ka, the dinocyst data suggest that the uppermost ocean remained dominated by cold waters until ~. 6.5. ka. A reduced advection of cold polar waters through the East Greenland/East Icelandic Current thereafter entailed warmest and most saline Holocene conditions between 6.5 and 5. ka, in turn followed by a general cooling trend. By contrast, both planktic foraminifers and dinocysts show an increased presence of Atlantic (-type) waters from ~. 122. ka onward resulting in a MIS 5e thermal optimum around 120.5. ka. Nonetheless, occasional freshwater input from melting drift ice created stratified but also seasonally variable conditions during this first half of MIS 5e. This stratification signature disappeared at ~. 120. ka when a marked repositioning of the oceanographic fronts occurred. Slightly colder conditions are indicated by both phyto- and zooplankton from there on until the end of MIS 5e around ~. 117. ka. A late MIS 5e cooling at the Iceland Plateau is opposite to a late MIS 5e optimum observed in the eastern Nordic seas. This regional difference is likely explained by various feedback mechanisms following the major reorganisation of the oceanic fronts at ~. 120. ka. The Holocene and MIS 5e interglacial variability is not reflected in the (quasi-monospecific) coccolith assemblages and illustrates the low sensitivity of living coccolithophore communities to subtle temperature changes in the low-temperature regions of the Nordic seas. Overall, quite different surface water properties appear to have characterised both interglacial intervals, with a higher share of warm, Atlantic elements in the planktic communities during MIS 5e. This suggests a higher contribution of Atlantic waters in the southwestern Nordic seas probably due to a more northward expansion of the Irminger Current under weakened polar East Greenland/East Icelandic currents. Such a reduced influence of polar waters in the southwestern Nordic seas may thus explain other evidence for relatively warm conditions in MIS 5e all around southern Greenland. © 2012 Elsevier B.V.

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