Stable isotope studies on ice cores and snow pits in DML, Antarctica, covering the past 2000 years

Hans.Oerter [ at ]


During the past 15 years various ice cores were drilled at and upstream of Kohnen station (75.0017 S, 0.0678 E, 2882 m a.s.l.) Dronning Maud Land, East Antarctica, supplemented by snow pit studies. These data sets of stable-isotope data (18O, D, deuterium excess d) are available over various time periods displaying centennial and strong decadal variations. 5 ice cores are used to create staked profiles of the deviation of the 18O content from the mean of the period 1259-1816 (an interval well defined by 2 unique volcanic events) for the time slices of the past 2000 and 200 years. For the past 50 years data from various shallow firn cores and snow pits in the area will be presented. The used reference period for the short term studies is 1961-1990. δ18O values may be converted to temperature with the local gradient of 0.77 δ18O-‰/°C. The Common Era follows the Roman period which is characterised by isotope values or temperatures, respectively, higher than observed in the 2000 years afterwards until today. The so-called medieval optimum around 1050-1250 is recognisable. The so-called Little Ice Age, which is attributed to the period 1650-1850 in the Northern hemisphere, is not clearly displayed. Overall, a slight cooling (0.008 δ18O-‰/100a) is evident within the Common Era until 1900. In the time slice of the past 200 years the coldest period occurred between 1875 and 1900. During the 20th century the isotope content and thus the air temperature have been increasing (0.88 δ18O-‰/100a) and reached values in the first decade of the 21st century clearly higher than around 1800 and before. The 1940ies formed the coldest decade in the 20th century, another relative minimum appeared in the 1980ies. The time series with shallow firn cores and snow pits stop at 2008 CE. For the past 50 years it is not possible to determine a trend unambiguously. This is due to the decadal variations and the shortness of the time series from single pits and shallow cores. However, if one compares 50years means for the past 2500 years, the half-century mean value for 1950-2000 (0.644 δ18O-‰ deviation from 1259-1816 average) was only exceeded twice, which happened in the Roman period. Averaging over 1955-2005 one gets the highest value (0.774 δ18O-‰ deviation) in the Common Era. Part if this work was carried out within the ESF PolarCLIMATE project HOLOCLIP with funding from the German Federal Ministry of Education and Research (BMBF).

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Conference (Poster)
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AGU Fall Meeting, 03 Dec 2012 - 07 Dec 2012, San Francisco, California, USA.
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Oerter, H. , Kipfstuhl, S. and Wilhelms, F. (2012): Stable isotope studies on ice cores and snow pits in DML, Antarctica, covering the past 2000 years , AGU Fall Meeting, San Francisco, California, USA, 3 December 2012 - 7 December 2012 .

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