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キーワード:
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要旨:
For modeled sediment cores of the open ocean, a method for predicting
simultaneously the ages of four different solid sediment compounds with
respect to their depositional year onto the sediment surface is presented.
The simulation of time-dependent age distribution in the sediment mixed
layer and the eventually accumulating sediment is a prerequisite of a
proper data assimilation of marine sediment core data into predictive
climate models. Through such a data assimilation, marine paleoclimate data
could then be efficiently used in order to optimally determine adjustable
model parameters. The age simulation is based on a passive tracer
transport method taking into account varying vertical advection rates
within the sediment top layers, chemical pore water reactions, and
bioturbation. It turns out that different weight fractions of the modeled
sediment have different ages in one horizontal geometric depth-in-core
level depending on the particle rain onto the sediment and the reactivity
of the material within the sediment pore waters. For simultaneous
consideration of paleoclimatic tracers associated within one and the same
weight fraction, e. g., for calcium carbonate, tracers such as
foraminiferal delta C-13, and calcium carbonate weight percentages, this
may not be critical. However, for simultaneous consideration of calcium
carbonate and opal weight percentages, the age difference in the observed
weight fractions may have to be corrected. The age offset between CaCO3
and opal depends critically on the sediment accumulation rate.
Low-accumulation sites are more strongly affected than high-accumulation
sites.
