The analyses of ice drilled in the Greenland ice sheet have revealed the occurrence of rapid climatic instabilities during the last glacial period, known as Dansgaard-Oeschger (DO) events. The imprint of DO events is also recorded at mid to low latitudes in different archives of the northern hemisphere. A detailed multiproxies study of the sequence of these rapid instabilities is essential for understanding the climate mechanisms at play. In this thesis, we combine water isotopes (d18O, d-excess and 17Oexcess) and air in Greenland ic cores (markers of temperature changes d15N, of land productivity d18Oatm, and also concentration and isotopic composition of methane) to quantify regional temperature changes in Greenland, to characterize the reorganization of the hydrological cycle and to better understand the role of the biosphere in climate feedbacks and the sequences of climatic events. Finally, we develop a multiproxies approach to identify in polar ice cores the fingerprint of Heinrich events (layers of ice rafted debris in North Atlantic marine cores, deposited by icebergs melt, caused by the collapse of Northern hemisphere ice sheets). Most of the new data presented in this thesis were obtained from the NEEM ice core, NW Greenland, drilled in 2008-2011 in the frame of an international project led by the Centre for Ice an Climate, Denmark.

Studying past climate change offers a valuable way of observing how the climate system responds to natural forcings. Ice cores from the polar regions are an excellent tool for investigating past climate, in part thanks to the unique archive of atmospheric air preserved in the glacial ice. The most abundant components of this air are, of course, nitrogen, oxygen, and argon, each of which records valuable information about past climate. This thesis explores the climate of the Last Glacial Period using measurements of the isotopic composition of nitrogen, oxygen, and argon in ice core air.Chapter 2 discusses fluctuations in the properties of the snow and firn at the South Pole during the past 30,000 years. The largest fluctuations are the result of past changes in katabatic wind speed linked to variations in surface topography upstream of the ice core site. In addition, the data, together with a series of modelling experiments, provide evidence that the ice core data are affected by a seasonal bias. The bias is also linked to past wind speed and topography at the ice core site and has the potential to impact other, similar ice core records. Chapter 3 utilizes ice core records of the isotopic composition of atmospheric oxygen to investigate the response of tropical hydroclimate and the terrestrial biosphere to abrupt climate change during the Last Glacial Period (Dansgaard-Oeschger and Heinrich Events). The data show that tropical precipitation and global photosynthetic oxygen production migrate northward and southward in response to abrupt warming and cooling in the North Atlantic, taking approximately 1,000 years to adjust to the new climate state. Chapter 4 presents an improved analytical method for making precise measurements of the isotopic and elemental ratios of nitrogen, oxygen, and argon in whole-air (i.e., without splitting or purifying the ice core air sample). The results are (i) a method capable of measuring the three gases with a precision suitable for detecting ice core signals, and (ii) recommendations for further development and application of the method to ice core samples. In sum, the findings presented here advance our understanding of how wind-speed and topography affect ice core gas records, how tropical hydroclimate and the terrestrial biosphere respond to abrupt climate change, and how to better make precise measurements of these gases in ice core samples.

The analysis of polar ice cores has proven to be very instructive about past environmental conditions on the time scale of several climatic cycles, and recent drilling operations have provided information of great value for global change issues. The book presents the most recent data extracted from Greenland ice cores and surface experiments and compares them with former Antarctic results. It contains background articles, original contributions and group reports of interest to scientists, climatologists, atmospheric chemists, and glaciologists involved in global change research.

The second revised edition of the Encyclopedia of Quaternary Science, Four Volume Set, provides both students and professionals with an up-to-date reference work on this important and highly varied area of research. There are lots of new articles, and many of the articles that appeared in the first edition have been updated to reflect advances in knowledge since 2006, when the original articles were written. The second edition will contain about 375 articles, written by leading experts around the world. This major reference work is richly illustrated with more than 3,000 illustrations, most of them in colour. Research in the Quaternary sciences has advanced greatly in the last 10 years, especially since topics like global climate change, geologic hazards and soil erosion were put high on the political agenda. This second edition builds upon its award-winning predecessor to provide the reader assured quality along with essential updated coverage Contains 357 broad-ranging articles (4310 pages) written at a level that allows undergraduate students to understand the material, while providing active researchers with a ready reference resource for information in the field. Facilitates teaching and learning The first edition was regarded by many as the most significant single overview of Quaternary science ever, yet Editor-in-Chief, Scott Elias, has managed to surpass that in this second edition by securing even more expert reviews whilst retaining his renowned editorial consistency that enables readers to navigates seamlessly from one unfamiliar topic to the next

Reviews the evidence underpinning the Anthropocene as a geological epoch written by the Anthropocene Working Group investigating it. The book discusses ongoing changes to the Earth system within the context of deep geological time, allowing a comparison between the global transition taking place today with major transitions in Earth history.