A sub-fossil coral Sr∕Ca record documents northward shifts of the Tropical Convergence Zone in the eastern Indian Ocean

• DOI: 10.5194/cp-21-211-2025
• Publication Date: 2025-01-28T08:19:17Z
• Authors: Miriam Pfeiffer; Hideko Takayanagi; Lars Reuning; Takaaki K. Watanabe; Saori Ito; Dieter Garbe-Schö...; Tsuyoshi Watanabe; Chung-Che Wu; Chuan-Chou Shen; Jens Zinke; Geert-Jan A. Brummer; Sri Yudawati Cahy...
• Keywords: Convergence zone; Tropical Atlantic; Intertropical Convergence Zone

Abstract. Sea surface temperature (SST) variability in the south-eastern tropical Indian Ocean is crucial for rainfall rim countries. A large body of literature has focused on zonal associated with Dipole (IOD) which peaks austral spring. In today's climate, northward shifts Tropical Convergence Zone (TCZ) co-vary IOD, and it unclear whether these may also occur independently. We have developed a new monthly resolved Sr/Ca record from sub-fossil coral cored at Enggano Island (Sumatra, Indonesia). Core sections containing diagenetic phases are omitted SST reconstruction. U/Th dating shows that Sr/Ca-based extends 1869–1918 1824–1862 relative age uncertainty ±3 years (2σ). At Island, coastal upwelling cooling spring impact seasonality coupled to latitudinal position TCZ. The indicates an increase between 1856 1918 1930–2008 period. attribute this enhanced due stronger south-easterly (SE) winds driven by shift TCZ nearby sediment core colder SSTs shallower thermocline prior ∼1930. These results consistent north–south gradient eastern Ocean, calculated historical data, not seen gradient. conclude relationship meridional non-stationary modulated long-term evolution gradients.