HR: 0800h
AN: C51A-1025    [Abstracts]
TI: Climate Signals and Trends in the Dasuopu Snow Accumulation Time Series Associated with the Indian Summer Monsoon, the Regional Hadley and Walker Circulations
AU: * Zhao, H
EM: clarck@atmosp.physics.utoronto.ca
AF: University of Toronto, 60 St. George Street, Toronto, ON M5S 1A7 Canada
AU: Moore, K
EM: moore@atmosp.physics.utoronto.ca
AF: University of Toronto, 60 St. George Street, Toronto, ON M5S 1A7 Canada
AB: A new climate record of potential interest in understanding climate variability is the snow accumulation time series from the Dasuopu ice core that is situated at an elevation of 7020m above sea level in the southern Himalayas ($28\deg$23'N, $85\deg$43'E). Snow accumulation at the site is thought to occur predominately during the summer season. In addition, snow accumulation is sufficiently high as to allow for the recovery of an annually resolved time series. In this talk, we will discuss the climate signals contained in this time series. Despite its proximity to the Indian subcontinent, we find no statistically significant relationship between the Dasuopu snow accumulation (DSA) and the Indian monsoon rainfall index (IMR) for the period 1956-1993. Furthermore, we find a statistically significant negative trend in the DSA during this period, while the IMR exhibited no such trend. We attribute these differences to the extreme height of the ice core site that effectively decouples snow accumulation at the site from the surface confined moisture transport that is associated with the Indian summer monsoon. On the other hand, we find statistically significant relationships between DSA and various indicators of the upper-level circulation associated with the monsoon. These results suggest that the DSA may contain an expression of the regional Hadley and Walker circulations. To confirm this hypothesis, we investigate the climate signal in the DSA that is associated with the global divergent circulation that contains information on the Hadley and Walker circulations. We find that there exist trends in the regional Hadley and Walker circulations that are consistent with the observed trend in the DSA. These changes are widespread and appear to be associated with reductions in West African and North China summer rainfall that have occurred during the latter half of the 20th century. These similarities lead us to conclude that the decreasing trends in the three precipitation time series during the latter half of the 20th century are the result of large-scale changes in the global overturning circulation that we propose are associated with large-scale changes in tropical sea surface temperatures.
DE: 3344 Paleoclimatology
DE: 3374 Tropical meteorology
DE: 3309 Climatology (1620)
DE: 1620 Climate dynamics (3309)
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting