HR: 10:20h
AN: PP12B-01 INVITED     [Abstracts]
TI: The 17 to 14 kyr ¹⁴C Decline
AU: * Broecker, W S
EM: broecker@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W/P.O. Box 1000, Palisades, NY 10964-8000 United States
AB: Much debate has occurred regarding the cause of the very high ¹⁴C to C ratios reconstructed for the period 30 to 40 kyrs. A corollary problem has to do with the decline in atmospheric ¹⁴C during the deglacial interval. In particular, the Δ¹⁴C drop from +400 to +200% between the time of H1 (~17,700 kyrs) and that of the onset of the Bolling-Allerod (~14,700 kyrs) is particularly hard to explain. The ice core ¹⁰Be record suggests that a drop in cosmogenic production can explain only a small part of this decline. The remainder has been attributed to the mixing between an isolated LGM abyssal reservoir and the remainder of the ocean. But ¹⁴C measurements on LGM benthic-planktic foraminifera pairs and ¹³C measurements on benthic foraminifera appear to rule out this scenario. Similarly, a massive methane injection can be ruled out. While tempting, the suggestion that the half-life of ¹⁴C is seriously in error is also highly unlikely.
DE: 1115 Radioisotope geochronology
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 3022 Marine sediments: processes and transport
DE: 4808 Chemical tracers
DE: 4901 Abrupt/rapid climate change (1605)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005