Pollen profile from sediment core KB1, Holzminden, Northern Germany

The Nachtigall clay pit near Holzminden, northern Germany, is located in a subrosional basin filled with 43 m of interglacial, interstadial and stadial deposits adjacent to the Weser River. The succession separates the Older Middle Terrace from the Younger Middle Terrace of the Weser River. Nachtigall core KB1 (1998) mainly contains silt and clay with intercalated peat layers. The layers of fen peat and intercalated humic silt are between 36 and 22.5 m depth. According to palynological studies, the peat layers and some humic silts were deposited during interglacial and interstadial periods marked by forest vegetation, termed Nachtigall 1 and Nachtigall 2. They are subdivided by a stadial, termed Albaxen. The peat of Nachtigall 1 is interrupted twice by silt and clay strata (Allochthonous Unit I, II) which are reworked sediments of older glacial periods, possibly of late Elsterian or early Holsteinian age. The palynological sequences of Nachtigall and Göttingen/Ottostrasse show the same pattern. Moreover, the contemporaneous pollen profiles of Nachtigall and Göttingen/Ottostrasse can be compared with the Velay pollen sequence (France). The Nachtigall core section 36-26.02 m corresponds to Bouchet 2 - Bonnefond - Bouchet 3 in Velay. The profiles of Velay and Nachtigall are independently correlated to the MIS-timescale and correspond to MIS 7c, 7b, and 7a. TIMS 230Th/U-dating shows ages ranging from 227 + 9/-8 to 201 + 15/-13 ka, which are in good agreement with the inferred MIS 7 age.

High-resolution FTIRS-inferred biogeochemical properties for MIS 11c in the sediment record of core ICDP5011-1 in Lake Elgygytgyn, NE Russia

Here we present a detailed multi-proxy record of the climate and environmental evolution at Lake El'gygytgyn, Far East Russian Arctic during the period 430-395 ka covering the marine isotope stage (MIS) 12/11 transition and the thermal maximum of super interglacial MIS 11c. The MIS 12/11 transition at Lake El'gygytgyn is characterized by initial warming followed by a cold reversal implying similarities to the last deglaciation. The thermal maximum of MIS 11c is characterized by full and remarkably stable interglacial conditions with mean temperatures of the warmest month (MTWM) ranging between ca. 10-15 °C; annual precipitation (PANN) ranging between ca. 300-600 mm; strong in-lake productivity coinciding with dark coniferous forests in the catchment; annual disintegration of the lake ice cover; and full mixis of the water column. Such conditions persisted, according to our age model, for ca. 27 ± 8 kyr between ca. 425-398 ka. The Lake El'gygytgyn record closely resembles the climate pattern recorded in Lake Baikal (SE Siberia) sediments and Antarctic ice cores, implying interhemispheric climate connectivity during MIS 11c.

Centennial-scale evolution of Dansgaard-Oeschger events in sediment core MD95-2006

There is much uncertainty surrounding the mechanisms that forced the abrupt climate fluctuations found in many palaeoclimate records during Marine Isotope Stage (MIS)-3. One of the processes thought to be involved in these events is the Atlantic Meridional Overturning Circulation (MOC), which exhibited large changes in its dominant mode throughout the last glacial period. Giant piston core MD95-2006 from the northeast Atlantic Ocean records a suite of palaeoceanographic proxies related to the activity of both surface and deep water masses through a period of MIS-3 when abrupt climate fluctuations were extremely pronounced. A two-stage progression of surface water warming during interstadial warm events is proposed, with initial warming related to the northward advection of a thin warm surface layer within the North Atlantic Current, which only extended into deeper surface layers as the interstadial progressed. Benthic foraminifera isotope data also show millennial-scale oscillations but of a different structure to the abrupt surface water changes. These changes are argued to partly be related to the influence of low-salinity deepwater brines. The influence of deepwater brines over the site of MD95-2006 reached a maximum at times of rapid warming of surface waters. This observation supports the suggestion that brine formation may have helped to destabilize the accumulation of warm, saline surface waters at low latitudes, helping to force the MOC into a warm mode of operation. The contribution of deepwater brines relative to other mechanisms proposed to alter the state of the MOC needs to be examined further in future studies.