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Inter-annual variability of mesoscale eddy occurrence in the western Arabian Sea Inter-annual variability of mesoscale eddy occurrence in the western Arabian Sea HOT

Inter-annual variability of mesoscale eddy occurrence in the western Arabian Sea

Sergey A. Piontkovski1*, Muna H.Al-Tarshi2 , Sabrina M.Al-Ismaili3 , Sultana S.H.Al-Jardani3 and Yasmin H.A.Al-Alawi3

1Sultan Qaboos University, P.O.Box 34, Muscat 123, Sultanate of Oman email:spiontkovski@gmail.com
2Ministry of Environment and Climate Affairs, P.O.Box 323, Muscat 100, Sultanate of Oman e-mail: biologypower@gmail.com
3 Ministry of Agriculture & Fisheries Wealth, P.O.Box 4271, Muscat 119, Sultanate of Oman e-mail: sabmohd86@gmail.com
*Corresponding author

Abstract
The western Arabian Sea is known for its intensive upwelling developed seasonally along the Omani coast as well as for numerous mesoscale eddies originating in and passing through waters with seasonally high or low primary productivity. The frequency of cyclonic and anticyclonic eddy occurrence for the 13 year period (from 2002 to 2015) retrieved with 4-km spatial resolution from MODIS-Aqua sea surface height anomalies, and data on wind speed, atmospheric anomalies, geostrophic currents and landings of large pelagic species (Yellowfin tuna, Kingfish and others) were analyzed, in order to elucidate the interannual variability and statistical linkages between parameters. The linear increase of eddy occurrence over years was observed during intermonsoon seasons, against the background of decreasing wind speed and the kinetic energy of the main geostrophic flow. Along with that, a positive correlation between the number of eddies and the variation of fish catches was elucidated. Presumably, the increasing number of cyclonic eddies could mediate the variance of fish catches, making them less predictable over years. The mechanism of this link could be based on the impact of cyclonic eddies on the oxycline depth. Concentrations of dissolved oxygen less than 1.5-2.5 ml L-1 reportedly act as the hypoxic threshold for the Yellowfin tuna. An enhanced number of cyclonic eddies could generate more heterogeneous spatial distribution of threshold concentrations- by lifting them to the upper layers and creating an unfavorable environment for populations of large pelagic species.

Keywords
Mesoscale eddies, Arabian Sea, fish landings, remote sensing, dissolved oxygen concentration

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Created 2019-02-18
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