Reconstructing precipitation in the tropical South Pacific from dinosterol 2H/1H ratios in lake sediment

The South Pacific Convergence Zone (SPCZ) is the Southern Hemisphere’s largest precipitation feature supplying freshwater to 11 million people. Despite its significance, little is known about the location and intensity of SPCZ precipitation prior to instrumental records, hindering attempts to predict precipitation changes in a warming world. Here we use sedimentary molecular fossils to establish a tool for extending the historical record of precipitation. Freshwater lake sediments and water samples were collected from 30 lakes that span a 4.6 mm d⁻¹ range in precipitation rates from the Global Precipitation Climatology Project (GPCP). δ²H_lakewater values from 29 lakes ranged from −29 to +23‰ and were inversely correlated (r = −0.51, p