What Causes the Postmonsoon 18O Depletion Over Bay of Bengal Head and Beyond?

Autor: Zhongyin Cai, Lide Tian
Jazyk: angličtina
Rok vydání: 2020
Předmět:
Zdroj: Geophysical Research Letters, Vol 47, Iss 4, Pp n/a-n/a (2020)
Druh dokumentu: article
ISSN: 1944-8007
0094-8276
DOI: 10.1029/2020GL086985
Popis: Abstract Modern observations from Bay of Bengal (BOB) head have shown that precipitation δ18O value reaches the lowest stage during late postmonsoon when the summer monsoon has weakened or retreated, complicating the traditional interpretation of low δ18O value as strong monsoon. We show that this postmonsoon 18O depletion phenomenon exists from BOB periphery to the southeast and south Tibetan Plateau. Accumulative precipitation along back‐trajectory still explains daily precipitation δ18O variability during both the monsoon and nonmonsoon, thus indicating that longer‐term weighted‐mean δ18O is biased toward synoptic conditions during precipitation events. Further, we propose that transport of moisture from the east (west) of the India‐Burma Trough leads to depleted (enriched) 18O during the postmonsoon (premonsoon). Our results reconcile the apparent contradiction but beg the consideration of potential bias and influence of different precipitation regimes in paleo archives.
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