An ice core record from the Guliya ice cap on the Qinghai-Tibetan Plateau provides evidence of regional climatic conditions over the last glacial cycle. 36 Cl data suggest that the deepest 20 meters of the core may be more than 500,000 years old. The δ 18 O change across Termination I is ∼5.4 per mil, similar to that in the Huascarán (Peru) and polar ice cores. Three Guliya interstadials (Stages 3, 5a, and 5c) are marked by increases in δ 18 O values similar to that of the Holocene and Eemian (∼124,000 years ago). The similarity of this pattern to that of CH 4 records from polar ice cores indicates that global CH 4 levels and the tropical hydrological cycle are linked. The Late Glacial Stage record contains numerous 200-year oscillations in δ 18 O values and in dust, NH 4 + , and NO 3 − levels.
Climatic influences on snow accumulation across the Tibetan Plateau are examined using records of net snow accumulation (A n ) and oxygen isotopic ratios (δ 18 O) since 1801 from two ice cores from opposite sides of the Plateau. From ∼1880 to the 1990s, summer monsoon precipitation has been a significant component of the annual accumulation on the Dasuopu glacier in the Himalayas, but during the latter part of the Little Ice Age (∼1810 to ∼1880) total A n was 30% higher than the summer monsoon amounts in northern India. This was possibly the result of increased early winter snowfall as westerly low‐pressure systems linked to the North Atlantic pushed farther east along the Himalayas than they normally do today. The decades of high accumulation and the colder temperatures allowed excess snow and ice to persist late into each year, which may have weakened the subsequent Asian summer monsoon. Consequently, precipitation in the northeast Tibetan Plateau where the Dunde ice cap is located may have been affected primarily by Eurasian continental processes rather than tropical meteorology during this time. Since the onset of the recent warming over the last century, the south Asian summer monsoon intensified and influenced summer climate farther to the north and west, and expressions of tropical Pacific and Indian Oceanic/atmospheric processes are noticeable in the Dunde net accumulation record. The Dunde and Dasuopu glaciers, which are located on the northern and southern rims of the Tibetan Plateau, were situated in regions of environmental transition as the Northern Hemisphere climate shifted from a neoglacial to a warming climate mode, which is something to consider when interpreting the longer ice core climate records.
A 480 year record of the oxygen-isotope ratios, dust content, chemical species and net accumulation from ice cores drilled in 1989 90 on Dyer Plateau in the Antarctic Peninsula is presented. The continuous analyses of small (sub-annual) samples reveal well-preserved annual variations in both sulfate content and δ 18 O, thus allowing an excellent time-scale to be established. This history reveals a recent pronounced warming in which the last two decades have been among the warmest in the last five centuries. Furthermore, unlike in East Antarctica, on Dyer Plateau conditions appear to have been fairly normal from AD 1500 to 1850 with cooler conditions from 1850 to 1930 and a warming trend dominating since 1930. Reconstructed annual layer thicknesses suggest an increase in net accumulation beginning early in the 19th century and continuing to the present. This intuitive conflict between increasing net accumulation and depleted δ 18 O (cooler climate) in the 19th century appears widespread in the peninsula region and challenges our understanding of the physical relationships among moisture sources, air temperatures and snow accumulation. The complex meteorological regime in the Antarctic Peninsula region complicates meaningful interpretation of proxy indicators and results in a strong imprint of local high-frequency processes upon the larger-scale climate picture.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)
