Data on climatic changes over thousands of years is needed for a better understanding of the shorter term variations which are of interest to man. For this purpose we measured the isotope composition (δD‰) of two adjacent ice cores drilled in the Dome C area. The time scale was established using the remarkably constant mean annual accumulation rate (37 kg m−2) determined by various techniques. The detailed isotope records were smoothed to filter out the δ value fluctuations not directly related to local temperature changes. With respect to conditions over the last 2.5 ka, the combined smoothed δ curve indicates a cooler climate from about 1800 to 1200 AD and a slightly warmer period from about 1200 to 700 AD. These periods may well correspond to the suggested world-wide Little Ice Age and medieval warm phase. Using the present δD‰/T°C measured at the surface, the maximum amplitude for these two periods, after smoothing with a low pass filter of 512 a, is approximately -0.35 and +0.3°C, respectively.
ABSTRACT. Deuterium, tritium, and gross fJ ac tivity measurements have been performed to a depth of 16 m on a snow core taken on Mont Blanc (French Alps) to establish a chronology of its formation and then d educe the annua l accumul a tion. These three independent methods show th a t the core was formed over a three-yea r period . This corresponds to a m ea n annual accumulation of 2.8 m water equivalent In addition, the isotopic measureme nts indicate the ex iste nce of a n altitude effect in the distribution of deuterium and tritium in the precipita tion in the Mont Bla nc area.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.