Objectives (2859/4000 characters, with spaces)
The overarching goal of the project is to quantify the influence of preformed trace metal
concentrations and therefore, by difference with observations, reveal the magnitude and spatial
patterns of metal-specific interior biogeochemical cycling processes such as remineralization and
scavenging, and quantify subsurface sources or sinks.
Objectives are separated into two groups: technical objectives (these are deliverable products)
and scientific objectives (these are hypothesis-driven).
I. Technical objectives:
a. Design a trace element specific end-member mixing model for use with GEOTRACES
data. The work will initially focus in the Atlantic, which is the basin with most data
coverage, though more GEOTRACES cruises have been (and will be) conducted in other
ocean basins and further data products will be released during the lifetime of this
fellowship, further extending the geographical scope of the proposed work.
b. Quantify the preformed contributions to GEOTRACES measurements in the Atlantic, and
provide uncertainty envelopes for these estimates.
c. Quantify the magnitude and establish the statistical significance of the spatial patterns of
the residual metal fractions (i.e differences between measured and preformed
concentrations) for each trace element individually and provide uncertainty envelopes for
these estimates.
d. Develop, document and release a freely available R-package called “geotraces” that will
allow others to perform/repeat the calculations from this work and help understand future
trace element data.
II. Scientific objectives:
a. Map and interpret residual metal fractions in the deep ocean by linking them to local
processes or path-integrated effects. Identify local sources and sinks, define and
differentiate the influence of biological remineralization and scavenging, characterize
hydrothermal inputs and hydrothermal scavenging. Use ancillary isotopic data as required
to inform the interpretation and collaborate with the data generators to the extent
possible.
b. Compare the magnitude and spatial patterns of the residual fractions between trace
elements, and with major nutrients, to quantify and understand variations in elemental
stoichiometry of the dissolved pool. Using these results, design and test new quasiconservative process tracers.
c. Develop a synthetic understanding of the role and importance of scavenging for the
cycling of trace metals in the sea using a combination of data analyses and model
experiments. Except for modeling studies, scavenging has typically been assumed to be
a one-dimensional vertical process in observational studies. This work will consider the
influence of advection explicitly and develop the theory of “scavection”, combining the
effects of scavenging and advection.
d. Investigate the role of seasonal variability in controlling the preformed trace metal flux.