SIBER SPIS sept 2011.pdf - IMBER

SIBER
Science Plan and Implementation Strategy
Scientific th e m e s
SIBER is structuring its research around six scientific themes, each focusing on a specific set
of issues that need to be addressed in order to improve understanding of the biogeochemical
and ecological dynamics of the IO and develop a predictive capability. These themes can be
broadly separated into three that are regionally focused (Themes 1-3) and three that address
wider scientific questions (Themes 4-6).
Re g i o n a l scientific t h e m e s
Th e m e 1: Bo u n d a r y c u r r e n t d y n a m i cs, i n t e r a c t i o ns a n d i m p a c ts
How are marine biogeochemical cycles and ecosystem processes in the IO influenced by
boundary current dynamics
Ba c k g r o u n d
Boundary currents mediate the transfer of global and regional forcings to local coastal scales.
In this process, they fundamentally alter biogeochemical fluxes and ecosystem processes.
One major mechanism is the generation of mesoscale eddies by boundary currents, which
in turn impinge on coastal regions with profound impacts. In the IO, several boundary current
systems are seasonally reversing (e.g. the Somali Current (SC), West (WICC) and East (EICC)
India Coastal Currents, and the Java Current (JC), Fig. 2). These reversing surface currents
are unique to monsoon-driven systems. The southern currents (Agulhas and Leeuwin) both
flow poleward throughout the year (Fi gs. 2, 8 a n d 9). The Leeuwin Current (LC) is particularly
anomalous in that it is the world’s only major eastern boundary current that flows poleward.
The LC is driven by the ITF (Fi gs. 2 a n d 8), which is a complex set of pathways that connect
the IO with the eastern Pacific (Domingues et al., 2007; McCreary et al., 2007). In general, the
biogeochemistry and ecology of southern hemisphere currents have been less comprehensively
studied than their northern counterparts and significant uncertainties still exist regarding their
dynamics and interactions.
The primary mechanisms whereby boundary currents impact ecosystems include control of
local water temperature, nutrient supply and mixed-layer depth. Impacts are influenced by the
intermediate water masses that feed boundary currents and therefore, determine their physical
and chemical properties. Boundary currents also mediate alongshore and cross-shelf transport
of whole planktonic ecosystems, including early growth stages of commercially important
finfish and shellfish species. Flow instabilities are commonly observed in boundary currents.
They can be initiated through interaction with shelf topography or develop spontaneously in
deeper waters. These instabilities give rise to mesoscale eddies, localized fronts or filaments,
all of which can mediate cross-shelf transport of nutrients and plankton communities. These
features can also form important aggregation points that promote larval recruitment and draw
fish and megafauna to regions of enhanced nutrients, plankton and food supply.
Biological variability in boundary current systems is driven by remote (e.g. propagation of
coastally trapped or open ocean Rossby waves) and local (e.g. coastal sea breezes by
diurnal land warming) forcings. It is important to disentangle the relative impacts of these
forcing mechanisms in future studies, particularly those aimed at assessing impacts of climate
variability and climate change on IO biogeochemistry and ecology. Since boundary current
systems are dynamic and complex, remote sensing and modeling are crucial investigative
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