HR: 12:05h
AN: PP12A-08    [Abstracts]
TI: The Adjustment of Ocean Tracers at Millennial Timescales
AU: * Gebbie, G
EM: gebbie@eps.harvard.edu
AF: Harvard University, 24 Oxford St., Cambridge, MA 02138,
AU: * Gebbie, G
EM: gebbie@eps.harvard.edu
AF: M.I.T., 77 Massachusetts Ave., Cambridge, MA 02139,
AU: Huybers, P
EM: phuybers@fas.harvard.edu
AF: Harvard University, 24 Oxford St., Cambridge, MA 02138,
AB: Interpretation of climate change as recorded in marine sediment cores requires an understanding of the advection, mixing, and (in some cases) decay of oceanic tracers. Even a steady-state ocean make take many millennia to come into full equilibrium with a surface anomaly, depending on the location of the anomaly and type of tracer. The problem is general and in some ways much studied, but here we introduce two novel aspects. One, we use a global ocean circulation model forced into consistency with a large collection of modern-day observations, as developed by the ECCO Consortium, to provide our most realistic guess at the circulation. Two, we attempt to provide further insight through an intercomparison of various measures of ocean timescales. In particular, we have conducted a very long simulation of the adjustment of conservative and radioactive tracers to surface anomalies over tens of thousands of years, and compare measures of the timescale of these adjustments as derived from radiocarbon activity, lead-lag relationships, equilibration timescales, and volume-filling rates. Furthermore, we demonstrate a Green function technique to reconstruct the transient response of a suite of tracers at any point in the ocean to arbitrary surface anomalies over many millennia. As a specific example, we consider how observations of benthic proxies lagging their planktic counterparts through the last deglaciation may be understood in the context of ocean adjustment timescales.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 4255 Numerical modeling (0545, 0560)
DE: 4532 General circulation (1218, 1222)
DE: 4860 Radioactivity and radioisotopes
DE: 4924 Geochemical tracers
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting