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This research proposal focuses on the role of the Southern Ocean in global change
and is submitted by
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<p><a href="presentation.htm"> BELCANTO </a>(BELgian research on Carbon uptake
in the ANTarctic Ocean) an existing interdisciplinary network of biologists,
geochemists, and physical and ecological modelers. The objective is to further
develop geochemical proxies and numerical tools for assessing and understanding
the present-day functioning of the CO<sub>2</sub> biological pump in the iron-limited
Southern Ocean and predicting its evolution in response to scenarios of increasing
atmospheric CO<sub>2</sub>. The research methodology will involve and combine
collection of historical and new field data, laboratory process-level studies
and numerical work in order to improve our understanding of the mechanisms controlling
the production of key bloom-forming phytoplankton groups of the Southern Ocean
(diatoms and Phaeocystis), their sinking rate and biodegradation when exported
in the mesopelagic zone (100-1000 m).<br>
Biological process and proxies investigations will be conducted under laboratory-controlled
conditions on cultures of key Antarctic phytoplankton (Fragilaria kerguelensis,
Chaetoceros brevis, Phaeocystis colonies and free-living cells) and bacteria
grown in sub-nanomolar-iron Southern Ocean waters and at low temperature (1
- 4°C). Biological studies will focus on the light and multiple nutrient
(Fe/NO3/NH4/Si) regulation of phytoplankton growth and sinking rate; on the
carbon and iron control of bacterial degradation of phytoplankton-derived material
including the mineralisation of nitrogen and biogenic silica. Proxies investigations
will focus on the use of Ba/Sr, f-ratio and isotopic signatures of C,
N, Si for tracing phytoplankton and diatom export production and will involve
measurements of Ba/Sr uptake and isotopic fractionation by cultured phytoplankton
for different growth and decay conditions. On this basis the relevance of each
proxy for tracing export production will be assessed and algorithms will be
developed for estimating export production from field measurements. abstract<br>
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Fieldwork will concentrate on the collection of new data on surface pCO<sub>2</sub>
and proxies measurements on suspended matter, collected particles in sediment
traps and sediment records. These data will be included in a data base collecting
existing data on pCO<sub>2</sub>, chlorophyll a, diatom/Phaeocystis distributions,
primary production and relevant proxies in order to reconstruct distribution
fields of atmospheric carbon uptake, bloom formation and export production in
the contemporary ocean.<br>
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Numerical work will involve the upgrading of the biogeochemical model
SWAMCO describing C, N, P, Si and Fe cycling through aggregated biological (diatoms,
nano-pico-phytoplankton, heterotrophic nanoflagellates, microzooplancton, bacteria)
of the surface layer and the subsequent export production at its lower boundary.
Upgrading will include the addition of Phaeocystis colonies as explicit state
variable and the implementation of a simple description of the phytoplankton-aggregation
process. Parameterisation will be obtained from process-level results. A simplified
version will be derived from model analysis for further coupling with a fine
grid (30-50km) version of a three-dimensional ice-ocean model. The application
domain will cover the region southward of 30°S. Initial and boundary conditions
for all state variables and atmospheric CO<sub>2</sub> will be derived from
existing global atmosphere-ocean models. Atmospheric iron supply will
be described as direct dust input or upon snow-ice melting. Model runs will
be conducted under present-day climatological forcing. Validation will be performed
by comparison of predictions with in situ observations (sea ice concentration,
temperature, salinity), reconstructed fields of surface chlorophyll a and primary
production derived from SEAWIFS, diatom/Phaeocystis distributions, and exported
production estimated by inverse modelling. Finally climate change prospective
scenarios with doubling atmospheric CO<sub>2</sub> will be conducted with initial/boundary
physical and biogeochemical conditions and atmospheric forcing obtained from
OBCM's runs. Results will be analysed with respect to regional and seasonal
changes of CO<sub>2</sub> sources and sinks. The resulting changes of sea-ice
cover, mixed-layer depth and surface circulation will be described and their
causes will be investigated by means of sensitivity experiments. Finally, the
impact of the resulting changing physical conditions on the behaviour of the
biological pump will be assessed. <a href="presentation.htm"> BELCANTO </a></p>
<p><a href="abstract.htm">Abstract</a></p>
<p><a href="deliverables.htm">deliverables</a></p>
<p><a href="meetings.htm">meetings</a></p>
<p><a href="objectives.htm">objectives</a></p>
<p><a href="publi_new.htm">publis</a></p>
<p><a href="biogas_frameset.htm">biogas</a></p>
<p><a href="partnership.htm">partnership</a></p>
<p><a href="frameset_iron_ammonium.htm">iron_ammonium</a></p>
<p> </p>
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