A 250-year SST and salinity coral record reflecting Indo-Pacific teleconnections by the Indonesian Throughflow

The tropical southeastern Indian Ocean regarded as a pivotal region for Indo-Pacific climate teleconnections, including phenomena such as the El Niño-Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD), and the Interdecadal Pacific Oscillation (IPO). However, long-term instrumental climate data are often lacking for tropical oceans. The geochemistry of massive stony corals provides a valuable record of past hydroclimatic conditions that compensates for this lack and surpasses existing data.

Using sub-seasonally resolved coral Sr/Ca and δ¹⁸O records from Browse Island, Australia spanning 1753–2011, this work provides new insights into sea surface temperature (SST) and salinity variability over interannual to multidecadal timescales. The Sr/Ca record reveals robust correlations with instrumental SST, capturing the long-term industrial era warming starting at the end of the Little Ice Age (LIA) and accelerating trends since the early 20^th century, indicative of anthropogenic forcing. The δ¹⁸O_seawater record, reconstructed from paired Sr/Ca and δ¹⁸O data, highlights hydrological variability driven by precipitation-evaporation dynamics, closely tied to the Australian monsoon, and ITF transport. While the imprint of the IOD seems to be reflected more in SST anomalies in the region, the influence of ENSO is recorded in hydrological anomalies due to changes in ocean advection. Long-term trends in δ¹⁸O_sw indicate centennial variability, reflecting complex interactions between monsoon-driven freshwater fluxes and ITF circulation. Freshening since the 1950s is likely caused by the intensified hydrological cycle due to anthropogenic warming. The SST reconstruction tracks the cooling and warming periods indicated by the IPO.  

The findings underscore the influence of interannual and decadal variability, particularly the IOD, ENSO, and the Interdecadal Pacific Oscillation (IPO), on SST and salinity, mediated by the combined effects of monsoon dynamics and ITF transport. Discrepancies between δ¹⁸O_sw and Sr/Ca-SST trends emphasize the need for further investigation into the driving mechanisms of long-term climate variability by pantropical teleconnections.