Western tropical Pacific hydrology as inferred from northern Borneo speleothems: interannual to orbital-scale variability
Wednesday, 16 December 2015: 17:30
2012 (Moscone West)
The response of large-scale convective systems in the tropics to anthropogenic climate change remains highly uncertain, even though a large number of paleo-hydrological reconstructions suggest that such systems are sensitive to a variety of past climate forcings across a wide range of timescales. In particular, absolutely-dated speleothems from across the tropics have documented systematic shifts in convective activity that occured in response to abrupt climate change and orbital forcing over the last several glacial-interglacial cycles. In Northern Borneo, overlapping decadally- to centennially-resolved stalagmite oxygen isotopic (d18O) records spanning the last 500,000 years reveal that regional convective activity in this region is dominated by fall precessional insolation forcing, with a significant contribution from abrupt climate change events whose signature is particularly pronounced immediately preceding glacial terminations (Partin et al., 2007; Meckler et al., 2012; Carolin et al., 2013; Carolin et al., in prep). High-resolution (sub-annual) oxygen isotope sampling of select intervals of the Holocene reveals that interannual variability is most reduced at ~5.2kybp, with relatively higher variance observed in the early and late Holocene (Chen et al., in prep). The fact that boreal fall insolation at the equator peaks at ~5kybp during the Holocene implies that the strong fall insolation signal in the longer Borneo stalagmite records may reflect the modulation of the El Nino-Southern Oscillation (ENSO) by fall insolation, given the sensitivity of modern-day rainfall and dripwater d18O to ENSO variability (Moerman et al., 2013; Moerman et al., 2014).