Climate Investigations Using Glaciochemical Records from a Tibetan Ice Core and a Fresh Snow Reconnaissance Study from Tierra del Fuego
As of 2002, Degree of Master of Science (MS) Quaternary and Climate Studies published under the auspices of the Climate Change Institute.
Glaciochemical records were retrieved and evaluated for a Tibetan ice core and fresh snow study in the Cordillera Darwin, Tierra del Fuego. The Tibetan ice core was collected during October and November 2005, in a joint-expedition between the University of Maine and the Institute of Tibetan Plateau Research (Chinese Academy of Sciences), from Guoqu Glacier on the northern side of Mt. Geladaindong. Statistical analysis of major ion time series suggests that atmospheric dust species dominate and that these dust levels are sufficiently high enough to conceal lesser marine ion species deposition. Annual and seasonal correlations between crustal ion time series and NCEP/NCAR Reanalysis variables (1948-2004) suggest that the Mt. Geladaindong record may contain local and regional surface pressure and air temperature proxies. The large decrease of dust baseline concentrations in the mid/late 1970s is accompanied by regional shifts in surface pressure, wind velocity, precipitation, and temperature and coincides with the major 1976/1977 shift of the Pacific Decadal Oscillation (PDO) from a negative to a positive state. This is the first ice core evidence of a potential teleconnection between central Asian atmospheric dust loading and the PDO. Analysis of longer ice cores from Mt. Geladaindong may enhance understanding of the relationship between the PDO and regional central Asian atmospheric circulation and subsequent atmospheric dust loading. The fresh snow sampling campaign was conducted by the University of Maine during the late austral summer of 2006 in the accumulation zone of Marinelli Glacier located in the Cordillera Darwin, Tierra del Fuego. Snow chemistry was dominantly loaded by marine species (CI-, Na+, and ssS042-). Na+ and Cl- accounted for ~70% of the total ion load and Na accounted for ~78% of total trace element loading. Contributions of crustal chemistry appear to be very low; nss Ca2+ only represents ~ 1% of the total ion load and nssCa, Al, and Fe represent approximately 6%, 4%, and 2% of the total trace element load, respectively. Empirical Orthogonal Function (EOF) analysis suggested two possible dust sources, one primarily represented by Al, and Fe and another by nssCa. Enrichment Factor (EF) calculations of trace elements suggested that the majority of elements are within average upper crustal ratios, however, major enrichments of Bi and Cd (hundreds of times) strongly suggest anthropogenic sources. Linear correlations of δ18O and on site barometric pressure (r=0.60 (p= 0.0066)) suggest a strong relationship between depleted δ18O ratios and stronger storm conditions. Back trajectory analysis shows air masses coming primarily from the west and southwest. Daily NCEP/NCAR Reanalysis composite maps revealed that passing cyclonic storms in the Drake Passage coincided with high sea salt (ss) species concentration at the site. The seasonality (higher ss concentrations during the summer) and dominance of marine species and concentrations of Ca2+ and N03 are similar to previous studies done in Patagonia. The glaciochemical records presented from Marinelli Glacier are the first measured in Tierra del Fuego, the southern most glaciated region outside of Antarctica.