Oman coral delta O-18 seawater record suggests that Western Indian Ocean upwelling uncouples from the Indian Ocean Dipole during the global-warming hiatus
The Indian Ocean Dipole (IOD) is an interannual mode of climate variability in the Indian Ocean that has intensified with 20th century global-warming. However, instrumental data shows a global-warming hiatus between the late-1990s and 2015. It is presently not clear how the global-warming hiatus affects modes of climate variability such as the IOD, and their basin-wide ocean-atmosphere teleconnections. Here, we present a 26-year long, biweekly record of Sr/Ca and delta O-18 from a Porites coral drilled in the Gulf of Oman. Sea surface temperature (SSTanom) is calculated from Sr/Ca ratios, and seawater delta O-18 (delta O-18(sw-anom)) is estimated by subtracting the temperature component from coral delta O-18. Our delta(18)Osw-anom record reveals a significant regime shift in 1999, towards lower mean delta O-18(sw) values, reflecting intensified upwelling in the western Indian Ocean. Prior to the 1999 regime shift, our SSTanom and delta O-18(sw-anom) show a clear IOD signature, with higher values in the summer of positive-IOD years due to weakened upwelling. The IOD signature in SSTanom and delta O-18(sw-anom) disappears with the overall intensification of upwelling after the 1999 regime shift. The inferred increase in upwelling is likely driven by an intensified Walker circulation during the global-warming hiatus. Upwelling in the Western Indian Ocean uncouples from the IOD.
1.Hokkaido Univ, Dept Nat Hist Sci, Fac Sci, Sapporo, Hokkaido 0600810, Japan 2.KIKAI Inst Coral Reef Sci, Kikai Town 8916151, Japan 3.Kyushu Univ, Dept Earth & Planetary Sci, Fac Sci, Fukuoka, Fukuoka 8190395, Japan 4.Christian Albrechts Univ Kiel, Inst Geowissensch, D-24118 Kiel, Germany 5.Sultan Qaboos Univ, Dept Marine Sci & Fisheries, Coll Agr & Marine Sci, Box 34,Al Khod 123, Muscat, Oman
Recommended Citation:
Watanabe, Takaaki K.,Watanabe, Tsuyoshi,Yamazaki, Atsuko,et al. Oman coral delta O-18 seawater record suggests that Western Indian Ocean upwelling uncouples from the Indian Ocean Dipole during the global-warming hiatus[J]. SCIENTIFIC REPORTS,2019-01-01,9