Summary of Abstract Submission

Abstract Submission No. IO50-04-0017PresentationPoster

INTERSEASONAL VARIABILITY IN THE SEA OF OMAN: A YEAR LONG GLIDER OCCUPATION

Bastien Y. Queste*1, Sergey A. Piontkovsky2, Karen J. Heywood1

1 University of East Anglia, UK
2 Sultan Qaboos University, Oman

ABSTRACT :

Three autonomous underwater gliders were deployed along an 80km transect extending out into the Gulf during both monsoons and the intermonsoon period as part of a joint ONR Global - NERC project. The gliders surveyed the top 1000m across the shelf, slope and open ocean. The gliders measured temperature, salinity, oxygen, chlorophyll a fluorescence, optical backscatter, photosynthetically active radiation and provided estimates of depth-averaged currents and up/downwelling. The across-shelf transect allowed estimation of along-slope transport of the Persian Gulf outflow, identified by its higher salinity, temperature, optical backscatter and oxygen content. The structure and volume of the outflow was highly variable. During peak outflow, the core extended beyond the glider transect. During periods of minimal flow, it was constrained to 10km beyond the shelf break. Persian Gulf outflow was also present in mesoscale eddies beyond the shelf break. The upper boundary of the oxygen minimum zone was determined by the volume of the Persian Gulf outflow, varying by up to 200m. The physical drivers of Persian Gulf outflow transport have a very clear and strong impact on the shelf ecosystem. Observations across the intermonsoon and both monsoon seasons revealed the interseasonal variability of production within the Sea of Oman. The gliders revealed a consistent and pronounced deep chlorophyll maximum at 45m. As production estimates in the region have previously relied on satellite ocean colour measurements which only resolve surface features, productivity has been significantly underestimated.