Different Dynamics Drive Indian Ocean Moisture to the Southern Slope of Central Himalayas: An Isotopic Approach

Abstract

This study uses precipitation oxygen isotopes (δ18Op) to examine key dynamics that deliver moisture to the southern slope of central Himalayas over different seasons. Results show that the majority of pre-monsoon δ18Op values are relatively high and controlled by the westerlies and local moisture. However, some abnormally low δ18Op values coincide with higher precipitation amounts during the pre-monsoon season due to moisture driven northwards from the Bay of Bengal and Arabian Sea to central Himalayas by anomalous circulations (quasi-anticyclone, anticyclone, or/and westerlies trough). The size and location of the quasi-anticyclone also influences the magnitude of the δ18Op decrease. In comparison, the monsoon δ18Op values are lower due to the combined effects of the Indian summer monsoon and convection. Our findings indicate that researchers need to consider the signals of abnormally low δ18Op values during the pre-monsoon season when attempting to interpret ice core and tree-ring records from central Himalayas.