Impact of dense-water flow over a sloping bottom on open-sea circulation: laboratory experiments and an Ionian Sea (Mediterranean) example

Abstract. The North Ionian Gyre (NIG) displays prominent inversions on decadal scales. We investigate the role of internal forcing induced by changes in horizontal pressure gradient due to varying density Adriatic Deep Water (AdDW), which spreads into deep layers northern Sea. In turn, AdDW fluctuates according circulation NIG through a feedback mechanism known as bimodal oscillating system. set up laboratory experiments with two-layer ambient fluid circular rotating tank, where densities 1000 and 1015 kg m?3 characterize upper lower layers, respectively. From potential vorticity evolution during dense-water outflow from marginal sea, we analyze response open-sea along-slope flow. addition, show some features cyclonic anticyclonic eddies that form layer over slope area. illustrate outcome discharge rates associated injection. When is high (1020 m?3) large, kinetic energy mean flow stronger than eddy energy. Conversely, when (1010 reduced, vortices are more energetic – is, larger general, slope, following onset injection, current shear develops layer. behaves fashion, thereby becoming Concurrently, flat-bottom portion basin, large-scale gyre forms extending partly toward sloping rim. record shows rise pycnocline sinking tank. rate increase proportional interface, namely decrease upper-layer thickness (i.e., squeezing). comparison Sea made for situation sudden switch basin-wide took place extremely dense water overflow after harsh winter 2012. how similar temporal vertical structure both oceanic conditions. demonstrated similarity further supports assertion wind-stress curl not paramount importance generating compared forcing.