Forcing of the Asian monsoon on the Tibetan Plateau: Evidence from high-resolution ice core and tropical coral records

Climatic influences on snow accumulation across the Tibetan Plateau are examined using records of net snow accumulation (A(n)) and oxygen isotopic ratios (delta(18)O) since 1801 from two ice cores from opposite sides of the Plateau. From similar to1880 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 (similar to1810 to similar to1880) 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.