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What Causes the Postmonsoon 18 O Depletion Over Bay of Bengal Head and Beyond?
Author(s) -
Cai Zhongyin,
Tian Lide
Publication year - 2020
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl086985
Subject(s) - bengal , monsoon , bay , precipitation , climatology , environmental science , atmospheric sciences , plateau (mathematics) , geology , oceanography , meteorology , geography , mathematics , mathematical analysis
Modern observations from Bay of Bengal (BOB) head have shown that precipitation δ 18 O value reaches the lowest stage during late postmonsoon when the summer monsoon has weakened or retreated, complicating the traditional interpretation of low δ 18 O value as strong monsoon. We show that this postmonsoon 18 O depletion phenomenon exists from BOB periphery to the southeast and south Tibetan Plateau. Accumulative precipitation along back‐trajectory still explains daily precipitation δ 18 O variability during both the monsoon and nonmonsoon, thus indicating that longer‐term weighted‐mean δ 18 O 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) 18 O 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.