Dajun Qin

Glaciochemical records from a Mt. Everest ice core: relationship to atmospheric circulation over Asia

Glaciochemical records recovered from an 80.4 m ice core in the East Rongbuk (ER) Glacier (elevation: 6450 m) on the northern slope of Mt. Everest provide a reconstructing of past climate for the period AD 1846–1997. Empirical orthogonal function (EOF) analysis on the eight major ion (SO4� ,M g 2+ ,C a 2+ ,N a + ,C l � ,N H 4 ,K + , and NO3 ) timeseries reveals inter-species relations and common structure within the ER glaciochemical data. The first two EOF series (EOF1-ions and EOF2-ions) are compared with instrumental data of sea level pressure (SLP) to demonstrate that the EOF-ions series display strong connections to winter (January) and summer (July) SLP over the Mongolian region. The positive relationship between EOF1-ions and the Mongolian High (MongHi) series suggests that enhanced winter MongHi strengthens the transport of dust aerosols southward from arid regions over central Asia to Mt. Everest. The close correspondence between EOF2-ions and the summer Mongolian Low (MongLow) indicates that the deeper MongLow, which is related to the stronger Indian Monsoon, contributes to a decrease in summer dust aerosols. Therefore, the ER ice core record comprises two assemblages of crustal species, each transported from different source regions during different seasons. EOF1-ions represents the majority of the crustal species and is related to winter atmospheric circulation patterns. These species are mainly transported from arid regions of central Asia during the winter dry season. EOF2-ions represents crustal species transported by summer atmospheric circulation from local/ regional sources in the northern and southern Himalayas. r 2002 Elsevier Science Ltd. All rights reserved.

Changes in chemical and isotopic properties near infiltrated cracks in an ice core from Urumqi glacier No. 1, Tien Shan, China

Abstract Ice cores recovered for paleoclimatic and/or paleoenvironmental reconstructions in the Tien Shan and Qinghai–Tibetan Plateau often encounter cracks. Although we expect that cracks opened to surface meltwater will inevitably change ice-core records, we do not know how and to what extent records are influenced. An ice core retrieved from glacier No. 1 at Ürümqi river head, Tien Shan, China, exhibits a crack nearly 2.5 m long that has admitted meltwater, forming secondary ice within the fracture. A small inclusion of the infiltrated ice in sampling is shown to reduce δ18O by an extent of Holocene vs Last Glacial Maximum while enhancing significantly the pH, conductivity and the following ionic species: CH3COO–, and CO(COO)2 2–. of the parameters increased, and HCOO– are the most affected, being enhanced nearly six-fold in the fractured section compared to the non-fractured sections, followed by CO(COO)2 2– and electrical conductivity measurement (ECM). Despite the alteration, primary fluctuations of some parameters are still recognizable. This suggests that if the infiltrated ice can be avoided in the sampling operation, ice cores with cracks may still provide authentic records. This shows the need to pay close attention to physical characteristics of ice cores in order to identify such secondary ice.

Past 43 year oxalate record: Urumqi Glacier No. 1, Tien Shan, China, and its link with far east Rongbuk Glacier, Qomolangma (Mount Everest)

Abstract A 43 year oxalate record has been recovered in a 14.08m ice core from Ürümqi glacier No. 1 (43˚06’N, 86˚49’ E), a mid-latitude glacier at Ürümqi river head, Tien Shan, western China. Averaging 3.6±9.2 ng g–1 the oxalate has a background level <2 ng g–1 with sporadic concentration enhancements. Most of the spikes reach beyond 10 ng g–1 and have durations 51 year. the oxalate variation correlates with that in Far East Rongbuk Glacier (27˚59’N, 86˚55’ E), Qomolangma (Mount Everest), which is located 1600 kmawayacross the Qinghai–Tibetan Plateau and Taklimakandesert. Although the concentration enhancement in the latter is much higher, and lasts longer, oxalate reaches its highest concentration in both cores at the same time, during winter. the correlation of oxalate records suggests that the two areas may have had the same kind of local sources, but with a much larger (COO)2 2– flux in the Qomolangma area, or that they may have had a common source in the Indian subcontinent through the longitudinal atmospheric circulation. the concentration variation in the past 40 years coincides with industrial/economic development in southern Asia, and is mainly due to anthropogenic pollution.