HR: 17:10h
AN: GC54B-07 INVITED [Abstracts]
TI: Vertical Mixing and Air-Sea 14CO2 Exchange in the Subtropics
AU: * Guilderson, T
EM: tguilder@ucsc.edu
AF: Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550, United
States
AU: * Guilderson, T
EM: tguilder@ucsc.edu
AF: Dept. of Ocean Sciences, UC Santa Cruz
1156 High Street, Santa Cruz, CA 95064, United States
AU: Wickett, M
EM: wickett@llnl.gov
AF: Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550, United
States
AU: Caldeira, K
EM: kcaldeira@globalecology.stanford.edu
AF: Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550, United
States
AU: Caldeira, K
EM: kcaldeira@globalecology.stanford.edu
AF: Dept. of Global Ecology, Carnegie Institution
260 Panama Street, Stanford, CA 94305, United States
AU: Schrag, D
EM: schrag@eps.harvard.edu
AF: Dept. of Earth & Planetary Sciences, Harvard University
20 Oxford Street, Cambridge, MA 02138, United States
AB:
We present a reconstruction of sub-tropical North Pacific surface water DELTA14C as recorded in a reef-building
hermatypic coral from near Keahoe Bay on the west side of the Big Island of Hawai'i. Between 1946 and 1992
sub-annually resolved samples document a dynamic range of 232‰. Mean annual pre-bomb values are -55‰
and a post-bomb maximum of 160‰ is observed in 1971. To explore the sensitivity of vertical mixing
parameterization schemes on subtropical air-sea CO2 exchange and the redistribution of anthropogenic CO2 as
reflected by the time-history of oceanic 14C, these and similar data from additional subtropical locations
(Bermuda, Rarotonga) are compared to DELTA14C simulated in a version of the Geophysical Fluid Dynamics
Laboratory (GFDL) ocean general circulation model. In the sensitivity tests presented here, we were surprised to
not find an adequate representation of the subtropical surface ocean 14C history and mixed layer depths, or at the
very least a clear "better" choice. This "generic" ocean model contains widely used parameterizations of ocean
mixing and is unable to successfully predict the surface DELTA14C time-history. These results imply a physical
flaw or bias in at the very least this OGCM and likely others that use similar numerical mixing schemes.
DE: 1030 Geochemical cycles (0330)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1620 Climate dynamics (0429, 3309)
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting