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Decoupling of seasonal temperature and precipitation over the western Pacific during the early mid‐Holocene
Author(s) -
Deng Wenfeng,
Wei Gangjian
Publication year - 2015
Publication title -
international journal of climatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.58
H-Index - 166
eISSN - 1097-0088
pISSN - 0899-8418
DOI - 10.1002/joc.4009
Subject(s) - holocene , coral , oceanography , climatology , sea surface temperature , precipitation , porites , geology , environmental science , geography , meteorology
This paper considers seasonal patterns of temperature and precipitation over the western Pacific during the early mid‐Holocene through an analysis of seasonal variations in sea surface temperature ( SST , reconstructed from coral Sr/Ca ratios) and seawater δ 18 O (δ 18 O sw , generated from coral Sr/Ca and δ 18 O ratios) in both modern corals and fossil corals from the early mid‐Holocene (ca. 6.7–6.5 ka Before Present (BP)). The modern coral, from the northern South China Sea ( SCS ) in the northwest Pacific, shows relatively negative δ 18 O sw values during the warmer seasons (May–December), but relatively positive values during the colder seasons (January–April). In contrast, the fossil coral shows relatively negative δ 18 O sw values during the cold seasons (February–May), but relatively positive values during the warm seasons (June–October). This contrast is also evident in the Vanuatu corals from the southwest Pacific. In detail, the modern coral record shows low δ 18 O sw values during most of the year, but with a positive δ 18 O sw peak in October (cold season), while the two early mid‐Holocene corals record a positive δ 18 O sw peak in February (summer) and a negative peak in August (winter). Seasonal patterns preserved in coral δ 18 O sw series reflect seasonal variations in precipitation, both in the northern SCS and Vanuatu; consequently, their contrasting seasonal coral δ 18 O sw variations during the early mid‐Holocene and at present indicate that the configuration of temperature and precipitation during the early mid‐Holocene differed to the present‐day situation. This decoupling of seasonal temperature and precipitation variations occurred over the western Pacific, which means that it was a regional, rather than simply a local climate phenomenon. This seasonal decoupling may have resulted from the synchronous northward shift of both the Intertropical Convergence Zone and South Pacific Convergence Zone during the early mid‐Holocene, which seems to be controlled by orbital forcing.