Glacial forcing of central Indonesian hydroclimate since 60,000 y B.P.

Abstract

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

The Towuti Drilling Project: paleoenvironments, biological evolution, and geomicrobiology of a tropical Pacific lake

“…Despite these advances, we lack long records of terrestrial paleoclimate from equatorial regions and particularly the Indo-Pacific. Previous sedimentary records from Lake Towuti span the last ∼ 60 kyr BP, and contain an intriguing record of past climate that differs markedly from that of the subtropics (Russell et al, 2014). In particular, we observed grassland expansion, lowered lake levels, and strong drying during the last glacial maximum (LGM) relative to both marine isotope stage 3 (∼ 30-60 kyr BP) and the Holocene (Costa et al, 2015;Konecky et al, 2016;Russell et al, 2014;Vogel et al, 2015).…”

“…1), a set of five ancient, tectonic lakes that have formed over the past ∼ 1.5 million years on the island of Sulawesi, Indonesia (Haffner et al, 2001;Lehmusluoto et al, 1995;Russell and Bijaksana, 2014). These are the oldest lakes in Indonesia and are thought to contain the longest continuous terrestrial records of climate in the Indo-Pacific Warm Pool (IPWP), a vast pool of warm surface waters in the western tropical Pacific.…”

“…Previous sedimentary records from Lake Towuti span the last ∼ 60 kyr BP, and contain an intriguing record of past climate that differs markedly from that of the subtropics (Russell et al, 2014). In particular, we observed grassland expansion, lowered lake levels, and strong drying during the last glacial maximum (LGM) relative to both marine isotope stage 3 (∼ 30-60 kyr BP) and the Holocene (Costa et al, 2015;Konecky et al, 2016;Russell et al, 2014;Vogel et al, 2015). The strong glacial-interglacial signal at Lake Towuti challenges the hypothesis that tropical hydroclimate is predominantly controlled by precessional orbital forcing, with little influence of glacial-interglacial changes in climate boundary conditions (Carolin et al, 2013;Meckler et al, 2012).…”

Continuous 1.3-million-year record of East African hydroclimate, and implications for patterns of evolution and biodiversity

“…Indeed, the markedly deepened megadrought behavior over the last 450,000 y in particular, resembles the tempo of enhanced northern hemisphere glacial-interglacial variability during that time interval, and suggests a strong linkage to highlatitude forcing and Indo-Arabian monsoon dynamics, as indicated in some shorter tropical records (21,23). The lack of steady precessional rhythms in this terrestrial hydroclimate record is consistent with recent modeling efforts (24) that suggest that moisture transport in southeastern Africa is a more complex and nuanced process than previously postulated, and orbital forcing alone (2,5,(25)(26)(27)(28)) is insufficient to explain 10 4-5 -y moisture variability over million-year time frames.…”

Evolution and forcing mechanisms of ENSO over the last 300,000 years in CCSM3

“…30 7b,c). Furthermore, sensitivity experiments show that the lowering of continental ice sheet can impact the tropical coupled ocean-atmosphere system significantly (e.g., Russell et al 2014;Lee et al 2014), leading to an intensified ENSO (Liu et al, Clim. Past Discuss., doi :10.5194/cp-2016-128, 2017 Manuscript under review for journal Clim.…”