HR: 17:15h
AN: PP54B-06    [Abstracts]
TI: High Latitude Forcing of Interior Ocean δ¹³C
AU: * Rutberg, R L
EM: rrutberg@geo.hunter.cuny.edu
AF: Hunter College, Department of Geography, 695 Park Ave, New York, NY 10021
AU: Peacock, S L
EM: synte@geosci.uchicago.edu
AF: University of Chicago, Department of Geophysical Sciences, 5734 S. Ellis Avenue, Chicago, IL 60615
AB: Transit time distribution probability density functions (TTDs) are used to investigate the relative roles of changing boundary conditions and changes in water mass distribution in setting the δ¹³C signal of the interior ocean. We use idealized examples to investigate the issue of tracer propagation from the surface ocean to interior ocean, and illustrate how a given boundary signal will be "filtered" with increasing distance from its source region. We show that tracers in the deep southeast Atlantic will respond much more strongly to changes in the Southern Ocean than to changes in the North Atlantic, while the opposite is true for waters at intermediate depths. The impact of a change in the Southern Ocean δ¹³C surface concentration on a δ¹³C profile from the western South Atlantic is estimated using model-derived transit-time distributions, and it is shown that significant deep ocean δ¹³C variations can be expected on glacial-interglacial timescales, even under a steady-state circulation regime. Records of surface δ¹³C from the North Atlantic and Southern Ocean are used to constrain changes in the surface ocean boundary condition on glacial-interglacial timescales. By convolving these boundary conditions with model-derived TTDs, we are able to explain a significant part of the observed variability in benthic δ¹³C records spanning the last glacial cycle(s) from the equatorial Atlantic Ocean , Cape Basin and the equatorial Pacific. This suggests that changing boundary conditions may be driving a significant fraction of benthic δ¹³C variability previously attributed to changes in ocean circulation. Furthermore, we show that our results predict a slightly higher δ¹³C than observed in high productivity regions, consistent with the concept of a productivity-induced low-δ¹³C overprint in high productivity regions.
DE: 4924 Geochemical tracers
DE: 4962 Thermohaline
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005