34 research outputs found
Snow chemistry across Antarctica
Un updated compilation of published and new data of major ion (Ca, Cl, K, Mg, Na, NO3, SO4) and methylsulfonate (MS) concentrations in snow from 520 Antarctic sites is provided by the national ITASE (International Trans-Antarctic Scientific Expedition) programmes of Australia, Brazil, China, Germany, Italy, Japan, Korea, New Zealand, Norway, United Kingdom, the United States, and the national Antarctic programme of Finland. The comparison shows that snow chemistry concentrations vary by up to four orders of magnitude across Antarctica and exhibit distinct geographical patterns. The Antarctic-wide comparison of glaciochemical records provides a unique opportunity to improve our understanding of the fundamental factors that ultimately control the chemistry of snow or ice samples. This paper aims to initiate data compilation and administration in order to provide a framework for facilitation of antarctic-wide snow chemistry discussions across all ITASE nations and other contributing groups. The data are made available through the ITASE web page (http://www2.umaine.edu/itase/content/syngroups/snowchem.html) and will be updated with new data as they are provided. In addition, recommendations for future research efforts are summarized
Tree ring δ18Oâs indication of a shift to a wetter climatesince the 1880s in the western Tianshan Mountainsof northwestern China
Central Asian droughts have drastically and significantly affected agriculture and water resource
management in these arid and semiarid areas. Based on tree ring δ18O from native, dominant Schrenk spruce
(Picea schrenkiana Fisch. et Mey.), we developed a 300 year (1710â2010) standard precipitation-evaporation
index (SPEI) reconstruction from January to August for Chinaâs western Tianshan Mountains. The regression
model explained 37.6% of the variation in the SPEI reconstruction during the calibration period from 1950 to
2010. Comparison with previous drought reconstructions confirmed the robustness of our reconstruction.
The 20th century has been a relatively wet period during the past 300 years. The SPEI showed quasi 2, 5, and
10 year cycles. Several pluvials and droughts with covariability over large areas were revealed clearly in the
reconstruction. The two longest pluvials (lasting for 12 years), separated by 50 years, appeared in the 1900s
and the 1960s. The most severe drought occurred from 1739 to 1761 and from 1886 to 1911 was the wettest
period since 1710. Compared to previous investigations of hydroclimatic changes in the western Tianshan
Mountains, our reconstruction revealed more low-frequency variability and indicated that climate in the
western Tianshan Mountains shifted from dry to wet in 1886. This regime shift was generally consistent with
other moisture reconstructions for the northeastern Tibetan Plateau and northern Pakistan and may have
resulted from a strengthened westerly circulation. The opposite hydrological trends in the western Tianshan
Mountains and southeastern Tibetan Plateau reveal a substantial influence of strengthened westerlies and
weakening of the Indian summer monsoon