SIBER SPIS sept 2011.pdf - IMBER
SIBER SPIS sept 2011.pdf - IMBER
SIBER SPIS sept 2011.pdf - IMBER
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<strong>SIBER</strong><br />
Science Plan and Implementation Strategy<br />
Mod e l i n g b i o g e o c h e m i c a l p r o c e s s e s, c l i m a t e v a r i a b i l i t y a n d l o n g-<br />
t e r m ch a n g e<br />
Much of the IO biogeochemical modeling effort so far has consisted of regional applications<br />
that have focused on the northern basin or its two sub-regions (Anderson et al., 2007; Hood<br />
et al., 2003; McCreary et al., 2001; McCreary et al., 1996; Sharada et al., 2008; e.g. Swathi et<br />
al., 2000; Vinayachandran et al., 2005). Only recently have region model applications outside<br />
of the northern IO been a focal point, primary example is the implementation of physicalbiogeochemical<br />
modeling applied to investigate how the MJO and IOD influence biological<br />
processes in the SCTR (Resplandy et al., 2009). In areas such as the SCTR where biological<br />
dynamics are largely localized to the deep chlorophyll maximum, the utility of ocean color<br />
measurements is reduced and the dependence on coupled physical-biogeochemical model<br />
applications to provide relevant insight is amplified.<br />
Obviously, satellites and coupled physical-biogeochemical models can both be applied to study<br />
planetary wave-induced chlorophyll and productivity responses in equatorial and subtropical<br />
waters, in a similar manner to analyses focusing on other ocean basins and the south eastern<br />
IO (e.g. Feng et al., 2009; Waite et al., 2007). Interestingly, a recent study of STIO physicalbiological<br />
interaction has documented a counterintuitive link between westward propagating<br />
Rossby waves in the 15-35°S band that stimulate primary productivity (based on SeaWiFSobserved<br />
chlorophyll) and exhibit an inverse correlation with tuna longline catches (White et<br />
al., 2004).<br />
Given the dramatic differences in the surface eddy kinetic energy between the AS and the<br />
BoB, modeling studies aimed at contrasting these two regions should provide good first-order<br />
information about dynamic differences. Coupled physical-biological models can also be applied<br />
to study biogeochemical and ecological responses to physical forcing. It has been shown<br />
that it is possible to capture first-order differences in the biogeochemical dynamics between<br />
the AS and the BoB with coupled models (Koné et al., 2009; Wiggert et al., 2006), although<br />
having sufficient resolution to resolve the observed variability, especially in the AS could be<br />
an issue. As discussed above, planned implementation of high-resolution (eddy-resolving)<br />
models in the IO (e.g. OFAM) will provide an excellent opportunity for performing comparative<br />
modeling studies of the AS and BoB using simple (NPZD-type) biogeochemical-ecological<br />
model formulations. These simple models are appropriate for assessing the leading-order<br />
biogeochemical differences between the two regions and can also be applied to study the<br />
biogeochemical and ecological impacts of semi-persistent or cyclical features, such as the<br />
Great Whirl, the Ras al Hadd Jet, the Laccadive High, the Sri Lanka Dome and the Wyrtki<br />
Jets.<br />
In addition to studies focused on surface variability, models can and should be applied to<br />
investigate intermediate and deepwater processes, i.e. linkages between surface production,<br />
export and remineralization and how these fuel and impact the OMZs in the AS and the<br />
BoB. Coupled models can be used to characterize first-order differences in these processes<br />
between the two basins. Similarly, studies should be undertaken that focus on the formation<br />
of the OMZs, and that aim to simulate the differences in the intensity and distribution of the<br />
OMZs between the AS and the BoB. Successfully simulating the subtle differences between<br />
the oxygen fields in these two basins is a significant research challenge and success in this<br />
endeavor would be an important first step toward understanding the balance of forcings that<br />
give rise to the OMZs in the AS and the BoB. Similarly, coupled models can be used to study<br />
export flux patterns and variability and first-order differences between the AS and the BoB.<br />
The lesser known OMZ that is present in the eastern Equatorial IO (Stramma et al., 2008)<br />
is also a feature of interest due to linkage with the Pacific Ocean through the ITF passage<br />
and the potential impact of the IOD that can significantly alter the quantity of organic matter<br />
exported vertically from the euphotic zone.<br />
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