Western tropical Pacific hydrology as inferred from northern Borneo speleothems: interannual to orbital-scale variability

Wednesday, 16 December 2015: 17:30
2012 (Moscone West)
Kim M Cobb1, Stacy Carolin2, Sang Chen3, David C Lund4, Anna Nele Meckler5, Jess F Adkins6, Sharon Susanna Hoffmann7, Julien Emile-Geay8, Andrew Tuen9, Alison Pritchard10, Brian Clark10, Jean Lynch-Stieglitz11, Jessica W Moerman1, Syria Lejau10 and Jenny Malang10, (1)Georgia Inst. of Technology, Atlanta, GA, United States, (2)Georgia Institute of Technology Main Campus, Atlanta, GA, United States, (3)University of Michigan Ann Arbor, Ann Arbor, MI, United States, (4)University of CT at Avery Point, Groton, CT, United States, (5)ETH Swiss Federal Institute of Technology Zurich, Zurich, Switzerland, (6)California Institute of Technology, Pasadena, CA, United States, (7)University of North Carolina at Wilmington, Wilmington, NC, United States, (8)University of Southern California, Los Angeles, CA, United States, (9)Universiti Malaysia Sarawak, Sarawak, Malaysia, (10)Gunung Mulu National Park, Mulu, Malaysia, (11)Georgia Institute of Technology Main Campus, Earth and Atmospheric Sciences, Atlanta, GA, United States
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).