Abstract. Since its discovery in Greenland ice cores, the millennial scale climatic variability of the last glacial period has been increasingly documented at all latitudes with studies focusing mainly on Marine Isotopic Stage 3 (MIS 3; 28-60 thousand of years before present, hereafter ka) and characterized by short Dansgaard-Oeschger (DO) events. Recent and new results obtained on the EPICA and NorthGRIP ice cores now precisely describe the rapid variations of Antarctic and Greenland temperature during MIS 5 (73.5-123 ka), a time period corresponding to relatively high sea level. The results display a succession of abrupt events associated with long Greenland InterStadial phases (GIS) enabling us to highlight a sub-millennial scale climatic variability depicted by (i) short-lived and abrupt warming events preceding some GIS (precursor-type events) and (ii) abrupt warming events at the end of some GIS (rebound-type events). The occurrence of these sub-millennial scale events is suggested to be driven by the insolation at high northern latitudes together with the internal forcing of ice sheets. Thanks to a recent NorthGRIP-EPICA Dronning Maud Land (EDML) common timescale over MIS 5, the bipolar sequence of climatic events can be established at millennial to sub-millennial timescale. This shows that for extraordinary long stadial durations the accompanying Antarctic warming amplitude cannot be described by a simple linear relationship between the two as Correspondence to: E. Capron (emilie.capron@lsce.ipsl.fr) expected from the bipolar seesaw concept. We also show that when ice sheets are extensive, Antarctica does not necessarily warm during the whole GS as the thermal bipolar seesaw model would predict, questioning the Greenland ice core temperature records as a proxy for AMOC changes throughout the glacial period.

Abstract. This paper presents and discusses the texture, fabric, water stable isotopes (δ 18 O, δD) and gas properties (total gas content, O 2 , N 2 , Ar, CO 2 , and CH 4 mixing ratios) of two climatically contrasted (Holocene vs. Pleistocene) ice wedges (IW-26 and IW-28) from Cape Mamontov Klyk, Laptev Sea, in northern Siberia. The two ice wedges display contrasting structures: one being of relatively "clean" ice and the other showing clean ice at its centre as well as debris-rich ice on both sides (referred to as "ice-sand wedge"). Our multiparametric approach allows discrimination between three different ice facies with specific signatures, suggesting different climatic and environmental conditions of formation and various intensities and nature of biological activity. More specifically, crystallography, total gas content and gas composition reveal variable levels of meltwater infiltration and contrasting contributions from anaerobic and aerobic conditions to the biological signatures. Stable isotope data are drawn on to discuss changes in paleoenvironmental conditions and in the temporal variation of the different moisture sources for the snow feeding into the ice wedges infillings. Our data set also supports the previous assumption that the ice wedge IW-28 was formed in Pleistocene and the ice wedge IW-26 in Holocene times. This study sheds more light on the conditions of ice wedge growth under changing environmental conditions.

Abstract. In low-accumulation regions, the reliability of δ18O-derived temperature signals from ice cores within the Holocene is unclear, primarily due to small Holocene climate changes relative to the intrinsic noise of the isotopic signal. In order to learn about the representativity of single ice cores and to optimise future ice-core-based climate reconstructions, we studied the stable-water isotope composition of firn at Kohnen station, Dronning Maud Land, Antarctica. Analysing δ18O in two 50 m long snow trenches allowed us to create an unprecedented, two-dimensional image characterising the isotopic variations from the centimetre to the hundred-metre scale. Our results show a clear seasonal layering of the isotopic composition, consistent with the accumulation rate, as well as high lateral isotopic variability caused by local stratigraphic noise. Based on the horizontal and vertical structure of the isotopic variations, we derive a statistical model for the stratigraphic noise. Our model successfully explains the trench data and allows to determine an upper bound of the reliability of climate reconstructions from seasonal to inter-annual time scales, depending on the number and the spacing of the cores taken. Implications for our study region include that reliably detecting a warming trend (0.1 °C decade−1) in 50 years of data would require ∼10–50 replicate cores with a horizontal spacing of at least 10 m. More generally, our results suggest that in order to obtain high-resolution records of Holocene temperature change, fast measurements, thus allowing multiple cores, are more important than to minimise analytic uncertainty as the latter only plays a minor role in the total uncertainty.

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Abstract. Jüngere Pegeldaten aus dem nordostdeutschen Ostsee-Küstenraum legen nahe, dass die eustatische Komponente der gegenwärtigen Meeresspiegeländerung überlagert wird durch eine räumlich differenzierte nicht-eustatische, insbesondere glazial- isostatisch, Komponente. Um zu untersuchen, in welchem Maße die frühere Meeresspiegelentwicklung durch diese beiden Komponenten beeinflusst wurde, wurde versucht, diese so weit zurück zu verfolgen, wie dies die Mächtigkeit der marinen Küstensedimentfolgen erlaubte. Drei neue relative Meeresspiegelkurven wurden abgeleitet, wovon zwei hier zum ersten Mal präsentiert werden. Die Kurven basieren auf zahlreichen AMS-Radiokohlenstoff-Datierungen von Meeresspiegel-Indexpunkten wie Basistorfen, archäologischen Unterwasserfunden und Torfprofilen aus Küstenüberflutungsmooren. Obwohl der Indikationswert der Proben aus den Küstenmooren wegen deren möglicher Kompaktion fraglich ist, konnten zuverlässige Angaben durch den Abgleich von Daten aus unterschiedlichen Ablagerungsräumen gewonnen werden. Die drei abgeleiteten Meeresspiegelkurven überdecken den Zeitraum von 6000 bis 7000 v. Chr. bis zur Gegenwart und divergieren gleichmäßig mit zunehmendem Alter. Ein Uferlinienverschiebungsdiagramm zeigt, dass tektonische Ereignisse dieses räumliche Bewegungsmuster nicht signifikant beeinflusst haben. Für die Bestimmung der isostatischen Komponente wurden die Meeresspiegelkurven verglichen mit einer von Denys/Baeteman (1995) publizierten Kurve für die belgische Küste, die als tektonisch und isostatisch stabiler gilt. Der Verlauf dieser Kurve wird daher hauptsächlich von der eustatischen Komponente bestimmt. Der Vergleich legt nahe, dass der SW-Abschnitt der deutschen Ostseeküste gegenwärtig eine leichte Submergenz aufweist, möglicherweise infolge eines sich rückbildenden, glazial bedingten Randwulstes. Im zentralen Abschnitt ist die isostatische Bewegung vor wenigen Tausend Jahren ausgeklungen, im nördlichen Abschnitt hält sie dagegen immer noch an. Hier beträgt die maximale Hebung während der letzten 9000 Jahre etwa 6 m relativ zur belgischen Küste.