The Indo-Pacific warm pool houses the largest zone of deep atmospheric convection on Earth and plays a critical role in global climate variations. Despite the region's importance, changes in Indo-Pacific hydroclimate on orbital timescales remain poorly constrained. Here we present high-resolution geochemical records of surface runoff and vegetation from sediment cores from Lake Towuti, on the island of Sulawesi in central Indonesia, that continuously span the past 60,000 y. We show that wet conditions and rainforest ecosystems on Sulawesi present during marine isotope stage 3 (MIS3) and the Holocene were interrupted by severe drying between ∼33,000 and 16,000 y B.P. when Northern Hemisphere ice sheets expanded and global temperatures cooled. Our record reveals little direct influence of precessional orbital forcing on regional climate, and the similarity between MIS3 and Holocene climates observed in Lake Towuti suggests that exposure of the Sunda Shelf has a weaker influence on regional hydroclimate and terrestrial ecosystems than suggested previously. We infer that hydrological variability in this part of Indonesia varies strongly in response to high-latitude climate forcing, likely through reorganizations of the monsoons and the position of the intertropical convergence zone. These findings suggest an important role for the tropical western Pacific in amplifying glacial-interglacial climate variability.tropical Pacific | paleoclimate | geochemistry | paleoecology

Lake Towuti (2.5°S, 121.5°E) is a longlived, tectonic lake located on the Island of Sulawesi, Indonesia, and in the center of the Indo-Pacific warm pool (IPWP). Lake Towuti is connected with upstream lakes Matano and Mahalona through the Mahalona River, which constitutes the largest inlet to the lake. The Mahalona River Delta is prograding into Lake Towuti's deep northern basin thus exerting significant control on depositional processes in the basin. We combine high-resolution seismic reflection and sedimentological datasets from a 19.8-m-long sediment piston core from the distal edge of this delta to characterize fluctuations in deltaic sedimentation during the past *29 kyr BP and their relation to climatic change. Our datasets reveal that, in the present, sedimentation is strongly influenced by deposition of laterally transported sediments sourced from the Mahalona River Delta. Variations in the amount of laterally transported sediments, as expressed by coarse fraction amounts in pelagic muds and turbidite recurrence rates and cumulative thicknesses, are primarily a function of lake-level induced delta slope instability and delta progradation into the basin. We infer lowest lake-levels between *29 and 16, a gradual lake level rise between *16 and 11, and high lake-levels between *11 and 0 kyr BP. Periods of highest turbidite deposition, *26 to 24 and *18 to Electronic supplementary material The online version of this article (16 kyr BP coincide with Heinrich events 2 and 1, respectively. Our lake-level reconstruction therefore supports previous observations based on geochemical hydroclimate proxies of a very dry last glacial and a wet Holocene in the region, and provides new evidence of millennial-scale variations in moisture balance in the IPWP.

Abstract. The Towuti Drilling Project (TDP) is an international research program, whose goal is to understand long-term environmental and climatic change in the tropical western Pacific, the impacts of geological andPublished by Copernicus Publications on behalf of the IODP and the ICDP. The Towuti Drilling Project environmental changes on the biological evolution of aquatic taxa, and the geomicrobiology and biogeochemistry of metal-rich, ultramafic-hosted lake sediments through the scientific drilling of Lake Towuti, southern Sulawesi, Indonesia. Lake Towuti is a large tectonic lake at the downstream end of the Malili lake system, a chain of five highly biodiverse lakes that are among the oldest lakes in Southeast Asia. In 2015 we carried out a scientific drilling program on Lake Towuti using the International Continental Scientific Drilling Program (ICDP) Deep Lakes Drilling System (DLDS). We recovered a total of ∼ 1018 m of core from 11 drilling sites with water depths ranging from 156 to 200 m. Recovery averaged 91.7 %, and the maximum drilling depth was 175 m below the lake floor, penetrating the entire sedimentary infill of the basin. Initial data from core and borehole logging indicate that these cores record the evolution of a highly dynamic tectonic and limnological system, with clear indications of orbital-scale climate variability during the mid-to late Pleistocene.

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