Statistics – Methodology
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufmgc24a..03t&link_type=abstract
American Geophysical Union, Fall Meeting 2006, abstract #GC24A-03
Statistics
Methodology
1105 Quaternary Geochronology, 4900 Paleoceanography (0473, 3344), 4901 Abrupt/Rapid Climate Change (1605), 4916 Corals (4220), 4934 Insolation Forcing
Scientific paper
The coral record of sea level change, which can be directly dated with U-series isotopes, has the potential resolve several crucial issues of climate change timing and cyclicity. By correcting coral ages for the well- documented age bias introduced by open-system behavior, a new level of accuracy and resolution can be achieved in sea level reconstruction. This new methodology has revealed both millennial and orbital cyclicity in the sea level record (Thompson and Goldstein 2005; Thompson and Goldstein in press, 2006). Here we present new coral ages from the Bahamas and Barbados. Multiple samples from individual corals and stratigraphic units allow a direct assessment of age reproducibility. The data document the reliability of corrected U/Th coral ages, which is in stark contrast to the conflicting results of conventional U/Th ages. The resulting sea level curve confirms significant millennial scale variability in sea level during the last interglacial. A similar mode of variability is observed during glacial periods and has been associated with the instability of the Laurentide ice sheet (Yokoyama et al. 2001; Chappell 2002). However, the persistence of such variability during both interglacial and glacial climate states suggests a climate driver that is independent of ice sheet dynamics. Perhaps millennial scale sea level events are driven by changes in the Earth's orbit. Millennial scale sea level variability might be driven by the interaction of high latitude summer insolation in both the southern and northern hemispheres, with millennial sea level events occurring at four times per precession cycle: when summer insolation in the N hemisphere is high, when summer insolation in the S hemisphere is high, and when summer insolation is roughly equal in both hemispheres, but changing rapidly in opposite directions. Here we test to see if this idea is a viable predictor of sea level events. Using the Imbrie and Imbrie (1980) model of ice volume with an average time constant of approximately 1 kyr and driven by 21 June insolation at 65N and 21 December insolation at 65S, we find that sea level highstands are statistically correlated with the maxima and minima of modeled ice volume in each hemisphere and with extrema in their rates of change. Chappell, J. (2002). "Sea level changes forced ice breakouts in the last glacial cycle; new results from coral terraces." Quat. Sci. Rev. 21(10): 1229-1240. Imbrie, J. and J. Z. Imbrie (1980). "Modeling the climatic response to orbital variations." Science 207: 943-953. Thompson, W. G. and S. L. Goldstein (2005). "Open-System Coral Ages Reveal Persistent Suborbital Sea- Level Cycles." Science 308(5720): 401-404. Thompson, W. G. and S. L. Goldstein (in press, 2006). "A radiometric calibration of the SPECMAP timescale." Quaternary Science Reviews. Yokoyama, Y., T. M. Esat and K. Lambeck (2001). "Coupled climate and sea-level changes deduced from Huon Peninsula coral terraces of the last ice age." Earth and Planetary Science Letters 193: 579-587.
Curran H. A.
Lisiecki L.
Thompson William G.
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