Oxygen Isotopes in <i>Tridacna</i> Shell Capture the Effect of the Indonesian Throughflow on Salinity in the Southern Timor Sea

Abstract Tridacna (giant clam) shell δ 18 O (δ 18 O Ts ) is a powerful proxy for reconstructing seasonal to interannual environmental changes before the Instrumental Era. However, the environmental controls on δ 18 O Ts in regions with significant hydrological changes are still ambiguous, and its potential for reconstructing large‐scale circulation variation has not been fully exploited. Here we present a 43‐year monthly resolution δ 18 O record of a modern Tridacna shell from the southern Timor Sea, and examined the linkages between the δ 18 O Ts and environmental parameters. The results indicate that annual δ 18 O Ts primally traces sea surface salinity variations associated with the Indonesian Throughflow (ITF). On interannual timescales, ENSO primally modulates ITF variation by altering the pressure gradient between the Western Pacific and Eastern Indian Ocean, which can be recorded in δ 18 O Ts . On decadal timescales, Pacific decadal oscillation primarily regulates the decadal variation of δ 18 O Ts by changing the ITF transport volume. Furthermore, the influence of the enhanced Walker Circulation from 1984 to 2013 on ITF transport is also imprinted in the δ 18 O Ts . Our study suggests that the δ 18 O Ts , from the areas where ITF flows, has the potential for recording past hydrological changes caused by the ITF variations.