Modelling cyclonic eddies in the Delagoa Bight region

Abstract

International audienceThe objective of this study is to document and shed light on the circulation around the Delagoa Bight region in the southern Mozambique Channel using a realistic modelling approach. A simulation including mesoscale forcings at the boundaries of our regional configuration succeeds in reproducing the general circulation in the region as well as the existence of a semi-permanent cyclonic eddy, whose existence is attested by in situ measurements in the Bight. Characterised by a persistent local minimum in SSH located around 26°S—34°E, this cyclonic eddy termed herein the Delagoa Bight lee eddy occurs about 25% of the time with no clear seasonal preference. Poleward moving cyclones, mostly generated further north, occur another 25% of the time in the Bight area. A tracking method applied to eddies generated in Delagoa Bight using model outputs as well as AVISO data confirms the model realism and provides additional statistics. The diameter of the eddy core varies between 61 and 147 km and the average life time exceeds 20 days. Additional model analyses reveal the systematic presence of negative vorticity in the Bight that can organise and form a Delagoa Bight lee eddy depending on the intensity of an intermittent southward flow along the shore and the spatial distribution of surrounding mesoscale features. In addition, the model solution shows other cyclonic eddies generated near Inhambane and eventually travelling through the Bight. Their generation and pathways appears to be linked with large Mozambique Channel rings

Seascape genetics of the spiny lobster Panulirus homarus in the Western Indian Ocean: Understanding how oceanographic features shape the genetic structure of species with high larval dispersal potential

“…A quasi‐stationary and topographically induced Delagoa Bight Eddy (Cossa et al, ; Halo et al, ; Lamont, Roberts, Barlow, Morris, & Berg, ; Lutjeharms & da Silva, ; Saetre & da Silva, ) creates strong upwelling and a cool Delagoa Bight cell, with near‐surface temperatures of <16°C at 150 m depth. The cell can potentially form a boundary that restricts gene flow between the two subspecies, but it is intermittent and therefore unlikely to be impermeable.…”

“…The Bight is a coastal indentation at the southern end of the Mozambique Channel, and both its location and unique oceanographic features may have contributed to the genetic discontinuity seen here. The Bight is affected by eddies moving gradually southwards through the Mozambique Channel, and also by cross‐channel eddies originating from the East Madagascar Current, on its path around the southern tip of Madagascar (Cossa, Pous, Penven, Capet, & Reason, ; Lutjeharms, ). Additionally, the Bight is located near the upper reaches of the Agulhas Current (Lutjeharms, ), and particles released here were frequently advected southwestwards.…”

“…Bight is affected by eddies moving gradually southwards through the Mozambique Channel, and also by cross-channel eddies originating from the East Madagascar Current, on its path around the southern tip of Madagascar (Cossa, Pous, Penven, Capet, & Reason, 2016;Lutjeharms, 2006). Additionally, the Bight is located near the upper reaches of the Agulhas Current (Lutjeharms, 2006), and particles released here were frequently advected southwestwards.…”

“…Eddy (Cossa et al, 2016;Halo et al, 2017;Lamont, Roberts, Barlow, Morris, & Berg, 2010;Lutjeharms & da Silva, 1988;Saetre & da Silva, 1984)…”

Model Perpindahan Vertikal Massa Air Oleh Interaksi Arus Dan Topografi Di Teluk Palu

“…Sirkulasi arus laut di Teluk Palu, selain yang dipengaruhi oleh Arlindo, juga dipengaruhi oleh tofografi Teluk Palu yang memiliki degradasi yang cukup tinggi. Degradasi kedalaman dapat menyebabkan aliran membentuk pusaran atau eddy oleh perlambatan kecepatan arus akibat gesekan dengan dasar perairan dan peningkatan kecepatan arus oleh pendakalan perairan [7,8].…”