Das Projekt "Chronologie der Vereisungen der noerdlichen und der suedlichen Hemisphaere" wird vom Umweltbundesamt gefördert und von Universität Bern, Geologisches Institut durchgeführt. A new radiocarbon chronology shows that piedmont glacier lobes in the Chilean Andes achieved maxima at 14500-14700; 21000;23100; 27500; 29000; and at least once higher 35000 years before present, all within a cold and wet Subatarctic Parkland environment. Massive glacier collapse, which began shortly before 14'350 years ago and was followed by an influx of North Patagonian Rain Forest species, terminated the last glaciation. In the Southern Part of New Zealand, an additional glacial maximum is recorded at 17'500 years before present, along with a Younger Dryas age readvance at 11050 years ago. These glacier peaks in South Pacific mid-latitude mountains replicate ice-rafting pulses in the North Atlantic Ocean. Further, the last termination began suddenly and simultaneously in both polar hemispheres prior to the resumption of the modern mode of deep-water production in the Nordic Seas. Such tight interhemispheric coupling is difficult to explain by regional North Atlantic events such as Laurentide ice-sheet surges or thermohaline switches. Rather, it implies global forcing that had its source in the atmosphere.
Das Projekt "Nord-Sued-Klimaverbindung und Kohlenstoffkreislauf waehrend der vergangenen 250000 Jahre" wird vom Umweltbundesamt gefördert und von Universität Bern, Physikalisches Institut, Abteilung für Klima- und Umweltphysik durchgeführt. Leading Questions: Is a period of stable and mild climate lasting 10000 years an exception? Are the rapid and drastic climatic changes observed in Greenland ice cores global events? How are global climatic changes coupled between the two hemispheres? Abstract: The aim of this proposal is to understand the dynamics of the climate system over the last 250,000 years, using an interactive approach between paleodata acquisition and modelling. A special emphasis is given lo the climatic interaction between the northern and southern hemispheres and the role of the carbon cycle. This includes - The reconstruction from existing bipolar (Antarctica and Greenland) ice cores of temperature changes as well as of different important climatic factors influencing the Earth's radiative balance greenhouse gases, ice volume, aerosols, - Modelling the isotopic composition of the precipitation and the dust cycle using AGCM, - Modelling climate and carbon cycle dynamics using a hierarchy of models to investigate the different mechanisms of the interhemispheric transmission of climate signals. The collaborative effort will allow - to describe with high resolution bipolar changes of climatic parameters observed from ice cores with a specific focus on interstadial and glacial-interglacial transitions, - to provide new information on greenhouse trace gas-climate interactions during the past, - to provide estimate of global climate sensitivity over the last 250 kyr, - to understand the mechanisms of the interhemispheric dynamics of the climate system, - to describe the temporal sequence of the processes generating the climate variability over climatic cycles, - to understand how and why the carbon cycle has undergone the variations observed on the paleoCO2 record. Benefits of this work will include a better understanding of the processes governing climatic and environmental changes and of climate sensitivity It will also provide data over a large range of climatic conditions, helping the validation of the climate models used for predicting future climate.