Wang Fei-teng

Preliminary results from measurements of selected trace metals in the snow-firn pack on Urumqi glacier No. 1, eastern Tien Shan, China

We present preliminary results on the occurrence of Pb, Cd, Zn, Al and Fe in dated samples collected from snow-firn packs at an altitude of 4130 m on Urumqi glacier No. 1, eastern Tien Shan. Extreme precautions for avoiding contamination were taken throughout the sampling, processing, transportation and analysis procedures. The concentrations of trace metals were determined by a double-focusing inductively coupled plasma mass spectrometer in an ultra-clean room. The average concentrations for these metals in surface snow are (in ng g -1 ): Pb, 2.4; Cd, 0.05; Zn, 10.0; Al, 100.0; and Fe, 130.0. These are higher concentrations (especially for Pb and Zn) than those in the polar and/or low- latitude remote areas. The data show that the input of trace metals to the snow has a clear seasonal change. Lower concentrations in surface snow can be found in July through September and higher concentrations from October to March, with an exception for January. The mean concentrations of the elements in the snow-firn pack also indicate seasonal variations and show a marked inverse relationship with temperature, possibly a result of meltwater percolation in the snow-firn pack.

Development of depth hoar and its effect on stable oxygen isotopic content in snow–firn stratigraphy on Ürümqi glacier No. 1, eastern Tien Shan, China

Abstract We report on the development of depth hoar and its relation to stable oxygen isotopic content in snow–firn stratigraphy in the percolation zone of Ürümqi glacier No. 1, eastern Tien Shan, China, during the period September 2004–August 2006. The essential condition for the development of depth hoar in the snow–firn pack is the temperature gradient. When the temperature gradient of the snow–firn pack reaches a maximum value of 13.0˚Cm–1 in mid-October, depth hoar begins to develop. By the end of March, the depth hoar might account for 25% of the total snow–firn pack depth. From April to June, as the weather becomes warm, the transport of water vapor diminishes and melting– regelation metamorphism replaces metamorphism caused by the temperature gradient. As a result, the depth hoar turns into coarse-grained firn. Fractionation of the oxygen isotopic content also occurs during formation of the depth hoar. The bottom 15 cm of the depth-hoar δ18O values were depleted in the lighter isotopic species as the snow sublimated from the lower to the upper crystals, and the δ values increased from –9.4% to –7.0% from 8 September 2004 to 25 January 2005. The upper 10 cm of the depth-hoar δ18O values were enriched in the lighter isotopic species and the δ values decreased from –6.8% to –9.3% during the same period.

Historical black carbon deposition in the Canadian High Arctic: a 190-year long ice-core record from Devon Island

Black carbon aerosol (BC), which is emitted from natural and anthropogenic sources (e.g., wildfires, coal burning), can contribute to magnify climate warming at high latitudes by darkening snowand ice-covered surfaces, and subsequently lowering their albedo. Therefore, modeling the atmospheric transport and deposition of BC to the Arctic is important, and historical archives of BC accumulation in polar ice can help to validate such modeling efforts. Here we present a > 250-year ice-core record of refractory BC (rBC) deposition on Devon ice cap, Canada, spanning the years from 1735 to 1992. This is the first such record ever developed from the Canadian Arctic. The estimated mean deposition flux of rBC on Devon ice cap for 1963–1990 is 0.2 mg m−2 a−1, which is at the low end of estimates from Greenland ice cores obtained using the same analytical method (∼ 0.1–4 mg m−2 a−1). The Devon ice cap rBC record also differs from the Greenland records in that it shows only a modest increase in rBC deposition during the 20th century. In the Greenland records a pronounced rise in rBC is observed from the 1880s to the 1910s, which is largely attributed to midlatitude coal burning emissions. The deposition of contaminants such as sulfate and lead increased on Devon ice cap in the 20th century but no concomitant rise in rBC is recorded in the ice. Part of the difference with Greenland could be due to local factors such as melt– freeze cycles on Devon ice cap that may limit the detection sensitivity of rBC analyses in melt-impacted core samples, and wind scouring of winter snow at the coring site. Air back-trajectory analyses also suggest that Devon ice cap receives BC from more distant North American and Eurasian sources than Greenland, and aerosol mixing and removal during long-range transport over the Arctic Ocean likely masks some of the specific BC source–receptor relationships. Findings from this study suggest that there could be a large variability in BC aerosol deposition across the Arctic region arising from different transport patterns. This variability needs to be accounted for when estimating the large-scale albedo lowering effect of BC deposition on Arctic snow/ice.

Depositional characteristics of NH4+ on Ürümqi glacier No. 1, eastern Tien Shan, China

Abstract Investigation into the depositional and post-depositional processes of atmospheric NH4 + on Ürümqi glacier No. 1 (UG1), China, was implemented within the Program for Glacier Processes Investigation (PGPI) campaign. Aerosol and surface snow samples were collected concurrently on a weekly basis from March 2004 to March 2005 in the UG1 accumulation zone at the headwaters of the Ürümqi river, eastern Tien Shan. All samples were analyzed for NH4 + and other chemical species. This paper investigates the seasonal variations of NH4 +. A significant linear relationship (R 2 = 0.70, N = 21, P < 0.01) between NH4 + concentrations in surface snow and aerosol was found during spring and summer, indicating that the warm–wet condition facilitates the air–snow exchange of NH4 +. Humidity was found to be a significant meteorological factor influencing NH4 + in deposition in autumn and winter. The NH4 + concentration in aerosol clearly shows a trend similar to that in surface snow, suggesting that the variation of atmospheric NH4 + might have been preserved in the surface snow. The possible source of NH4 + is discussed in this paper.