Stable-Isotope and Trace Element Time Series from Fedchenko Glacier (Pamirs) Snow/Firn Cores

In summer 2005, two pilot snow/firn cores were obtained at 5365 and 5206 m a.s.l. on Fedchenko glacier, Pamirs, Tajikistan, the world's longest and deepest alpine glacier. The well-defined seasonal layering appearing in stable-isotope and trace element distribution identified the physical links controlling the climate and aerosol concentration signals. Air temperature and humidity/precipitation were the primary determinants of stable-isotope ratios. Most precipitation over the Pamirs originated in the Atlantic. In summer, water vapor was re-evaporated from semi-arid regions in central Eurasia. The semi-arid regions contribute to non-soluble aerosol loading in snow accumulated on Fedchenko glacier. In the Pamir core, concentrations of rare earth elements, major and other elements were less than those in the Tien Shan but greater than those in Antarctica, Greenland, the Alps and the Altai. The content of heavy metals in the Fedchenko cores is 2-14 times lower than in the Altai glaciers. Loess from Afghan-Tajik deposits is the predominant lithogenic material transported to the Pamirs. Trace elements generally showed that aerosol concentration tended to increase on the windward slopes during dust storms but tended to decrease with altitude under clear conditions. The trace element profile documented one of the most severe droughts in the 20th century.

The 1452 or 1453 A.D. Kuwae Eruption Signal Derived from Multiple Ice Core Records: Greatest Volcanic Sulfate Event of the Past 700 Years

We combined 33 ice core records, 13 from the Northern Hemisphere and 20 from the Southern Hemisphere, to determine the timing and magnitude of the great Kuwae eruption in the mid-15th century. We extracted volcanic deposition signals by applying a high-pass loess filter to the time series and examining peaks that exceed twice the 31 year running median absolute deviation. By accounting for the dating uncertainties associated with each record, these ice core records together reveal a large volcanogenic acid deposition event during 1453 - 1457 A. D. The results suggest only one major stratospheric injection from the Kuwae eruption and confirm previous findings that the Kuwae eruption took place in late 1452 or early 1453, which may serve as a reference to evaluate and improve the dating of ice core records. The average total sulfate deposition from the Kuwae eruption was 93 kg SO4/km(2) in Antarctica and 25 kg SO4/km(2) in Greenland. The deposition in Greenland was probably underestimated since it was the average value of only two northern Greenland sites with very low accumulation rates. After taking the spatial variation into consideration, the average Kuwae deposition in Greenland was estimated to be 45 kg SO4/km(2). By applying the same technique to the other major eruptions of the past 700 years our result suggests that the Kuwae eruption was the largest stratospheric sulfate event of that period, probably surpassing the total sulfate deposition of the Tambora eruption of 1815, which produced 59 kg SO4/km(2) in Antarctica and 50 kg SO4/km(2) in Greenland.