Abstract
Abstract. The Persian Gulf produces high-salinity water (Persian Gulf Water, PGW hereafter), which flows into the Sea of Oman via the Strait of Hormuz. Beyond the Strait of Hormuz, the PGW cascades down the continental slope and spreads in the Sea of Oman under the influence of the energetic mesoscale eddies. The PGW outflow has different thermohaline characteristics and pathways, depending on the season. In spring 2011, the Phys-Indien experiment was carried out in the Arabian Sea and in the Sea of Oman. The Phys-Indien 2011 measurements, as well as satellite observations, are used here to characterize the circulation induced by the eddy field and its impact on the PGW pathway and evolution. During the spring intermonsoon, an anticyclonic eddy is often observed at the mouth of the Sea of Oman. It creates a front between the eastern and western parts of the basin. This structure was observed in 2011 during the Phys-Indien experiment. Two energetic eddies were also present along the southern Omani coast in the Arabian Sea. At their peripheries, ribbons of freshwater and cold water were found due to the stirring created by the eddies. The PGW characteristics are strongly influenced by these eddies. In the western Sea of Oman, in 2011, the PGW was fragmented into filaments and submesoscale eddies. It also recirculated locally, thus creating salty layers with different densities. In the Arabian Sea, a highly saline submesoscale lens was recorded offshore. Its characteristics are analyzed here and possible origins are proposed. The recurrence of such lenses in the Arabian Sea is also briefly examined.
Highlights
The Indian Ocean, the third tropical basin in size, is bounded to the north by the Asian landmass
This study focuses on two of them, the Sea of Oman and the Arabian Sea
This study focuses on the measurements in the northwestern Arabian Sea and in the Sea of Oman, in March 2011
Summary
The Indian Ocean, the third tropical basin in size, is bounded to the north by the Asian landmass. Al Saafani et al (2007) identified eddies in the Gulf of Aden generated by Rossby waves emitted from the Indian coast or amplified in the interior of the basin This mechanism is present in the northern Arabian Sea, with Rossby waves being forced by wind and by coastal Kelvin waves (see L’Hégaret et al, 2015). ARGO floats (see Carton et al, 2012; L’Hégaret et al, 2013) and HYCOM numerical simulations (see L’Hégaret et al, 2015) confirmed that during other seasons, PGW can be expelled from the coast into the Sea of Oman These ejections were related to the presence of mesoscale eddies in the Sea of Oman, and especially to the presence of a dipole in spring; different offshore ejection mechanisms were identified. The in situ observations give a finer-scale, but instantaneous, description of the eddies and water masses
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