SIBER SPIS sept 2011.pdf - IMBER

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SIBER Science Plan and Implementation Strategy XBT lines, in combination with Argo floats, are an effective means for developing heat, freshwater and momentum budgets of the upper ocean, providing a method for monitoring and understanding the role of ocean dynamics in climate variations. They are also effective for monitoring specific areas, such as the upwelling zones of Java/Sumatra and the SCTR that are regions of biogeochemical and ecological interest that exhibit clear sensitivity to climate variability. XBT survey lines also provide long-term monitoring of the ITF, which represents the principal exchange pathway between the IO and the tropical Pacific (Fig. 24). The XBT network is now largely operated by national agencies and is coordinated by the Ship of Opportunity Programme Implementation Panel (SOOPIP, http://www.ifremer.fr/ird/soopip/) under the Joint Committee for Oceanography and Marine Meteorology (JCOMM) (http://ioc.unesco.org/goos/ jcomm.htm). A potential opportunity exists whereby the ships of opportunity used in the XBT deployments could be leveraged as platforms for carrying out parallel biological and chemical measurements, i.e. using surface flow-through chlorophyll-fluorescence and underway measurements (e.g. Lee et al., 2000) and by towing instruments such as a continuous plankton recorder (CPR). Hydrographic survey and mooring support cruises also provide potential leveraging opportunities for carrying out biogeochemical and ecological studies in the equatorial and southern tropical waters of the IO. Mooring support operations, in particular, afford the possibility of coordinating activities such that focused process studies in the vicinity of the mooring location could be incorporated into the overall cruise plan. The CIRENE cruise represents a prime example of such a merger of coordinated mooring support and physical and biogeochemical sampling effort (Vialard et al., 2009). A follow up to the CIRENE effort is planned; this activity is also being designed as a means of combining RAMA mooring support with intensive in situ physical and biogeochemical sampling that would transect the STIO along 8°S (J. Vialard, personal communication). In general, such mergers of buoy maintenance and targeted in situ studies are a cost effective means of obtaining biological and chemical samples that help justify the maintenance costs of the RAMA array. Christmas Island provides a good potential location for staging studies not only in the Java Current but also in the inflow region of the ITF. Similarly, manpower and resources on Cocos Island (Australian weather station) could be leveraged for SIBER-related research. Routine commercial freighter traffic through the ITF region transiting to China provides the potential for ships of opportunity sampling, i.e. routine biological and chemical monitoring of surface waters in the ITF region and specifically through the Lombok Strait. More generally, SIBER planning must also include documentation of existing infrastructure around the IO basin and synthesis of information on current/planned observational resources. There are upcoming studies by Indian scientists in the Andaman Islands focusing on dynamics and physics. Of relevance here is the question of whether or not there are tide gauges along the Andaman Islands that could provide insights into coastal wave propagation. The SIBER program recommends that investigating and enabling this possibility should be a priority. Also of interest and potential relevance is a US military base on Diego Garcia, an atoll within the Chagos Island archipelago located about 1000 miles south of Sri Lanka. Would it be possible to make use of this facility as a staging area and for supporting SIBER (and IndOOS)-related research in equatorial waters Similarly, Reunion Island (France), Seychelles and Mauritius could possibly act as staging areas for SIBER-related research activities in the western basin. In addition to IndOOS, GOOS is promoting and coordinating several national efforts to establish coastal observing systems around the IO rim. These include SEAGOOS (southeast Asia), NEAR-GOOS and INAGOOS in the northeast Asia and Indonesian regions, and WAGOOS in the west Australian region. SIBER should endeavor to support and participate in all these regional efforts to help establish and coordinate coastal and open ocean biogeochemical and ecological time series measurements in the IO. 60
SIBER Science Plan and Implementation Strategy New in si t u ob s e r v a t i o n s Glider technologies are highly relevant and applicable, in particular to boundary current studies, as they cross all the time and space scales of interest and can be deployed and retrieved in coastal waters. Although there are still some technical issues, compact optical sensors are now available that can be deployed on gliders for measuring chlorophyll fluorescence, back scatter, CDOM and other chemical properties, thus providing the means to obtain co-located physical and biogeochemical measurements. In the future these types of sensors may also be linked to higher trophic level studies via dynamic coupling of tracking devices on animals to glider navigation (O. Schofield, personal communication). Although high technology sampling devices, such as gliders, can be used to augment time series measurements (adding a spatial dimension), these technologies are not (at present) ideally suited for making long-term measurements and they are too expensive for many IO rim countries to maintain and operate. This is in contrast to the low technology approach of taking a suite of simple water quality measurements (temperature, chlorophyll, nutrients, light penetration and zooplankton biomass) periodically from ships or small vessels that can operate in coastal waters. The latter is in the realm of feasibility for many IO rim nations, including developing countries. Time series also need to be established to measure basic atmospheric parameters, including aeolian material inputs into the IO. However, obtaining atmospheric measurements adds another level of expense and effort to time series measurements and requires appropriate sampling platforms (i.e. ships with atmospheric sampling towers, etc.). These measurements are very likely only feasible for countries with established oceanographic research facilities and ships. Atmospheric measurements are being initiated by NIO to supplement the oceanographic data from its shallow water time series station in the AS. Pro c e s s st u d i e s Successfully leveraging IndOOS would provide both an opportunity for obtaining long-term in situ biogeochemical and ecological observations and the possibility of acquiring time series measurements and real-time monitoring of biogeochemical and ecological properties in equatorial waters that could in turn provide a foundation for carrying out focused process studies. Utilizing long-term mooring-based physical and biogeochemical measurements as context for short-term, intensive physical and biogeochemical process studies is a powerful approach that can be applied to investigations of many of the equatorial forcing phenomena described above. For example, a broader understanding of IOD impact could be obtained through the combined use of satellite observations, objectively analyzed Argo float data, IndOOS/RAMA monitoring of physical properties over broad areas of the equatorial IO and strategically placed mooring-based biogeochemical measurements (see Appendix IV). Such continuous measurements could then be augmented with specific ship-based process studies aimed at more fully contrasting basinwide IOD biogeochemical and ecological impacts against typical annual evolution of these processes. The MJO, Wyrkti Jets, off-equatorial planetary waves and variability in the SCTR could all be studied using similar approaches. Organized comparative process studies are also needed in the AS and the BoB. These should include observations at fixed stations along fixed transacts as well as large-scale regional surveys. A strategy for observations in the AS is proposed below involving repeat samplings at the Indian time series sites and along a transect extending offshore from the Omani coast. A similar long-term monitoring program should also be implemented in the BoB. NIO in Goa, India has already initiated time series data collection off Visakhapatnam (located on the east coast of India). However, time series measurements from waters beyond the shelf break are also critically needed. In the immediate future, planned cruises include observations in both the AS and BoB under the GEOTRACES program, however problems with piracy in the western AS and equatorial waters will very likely impact AS cruises (discussed further below). 61
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