On the descent of dense water on a complex canyon system in the southern Adriatic basin.

Using the results of a numerical modelforthedescriptionofbottom-arrestedcurrentsandstatistical analyses,we elucidate different characteristics of the dynamics of a southward propagating vein ofNorth Adriatic DenseWater(NAdDW)observedtoevolvewithinacomplexcanyonsystemofthesouthern Adriatic basin.The vein,monitored from March2004 toMarch2005 by three distinct mooring lines, exhibitsacomplex,highly time-dependent dynamicscharacterizedbylargevelocityanddensity fluctuations.Inparticular,lagcorrelation analyses performedontheobservedvelocityandtemperature data showthatatemporallagrangingbetween7and10hgovernstheNAdDWsignalpropagationalong the differentcanyons,itsmagnitudeinverselydependingonveindownslopevelocitiesanddensity anomalies.Theperformedmodelsimulationsrevealthat,weaklydependingonitsinitiallayerthickness, exact position,anddensitycontrastwiththeupperocean,acoherentflowofdensewaterlocated upstreamofthecanyonsystemontheItalianshelfwillalwaysbifurcateattheentranceofthatsystem; while itsshallowerpartwilldisintegrateintoseveralbranches,itsdeeperpartwillcontinuetoflowmore coherently,injectingpartofthebottomwaterdownward.Regionsdominatedbysupercriticalflow regimesaresimulated,whichcontributestoexplainpartoftheobservedflowvariability.Simulatedlag times betweensignalspropagatinginthecanyonsareconsistentwithobservations.Theyarefoundto dependcruciallyoninitial,upstreamveinlocation,layerthickness,anddensitycontrastwiththeupper ocean. We finally use this information, retrievedbyour numerical simulations on the basis of the available observations,toinfer,inakindofinverseproblemsolving,possibleshape,location,anddensitycontrast possessedbythe observed vein of NAdDW onthe Italian continental shelf, priortoitssinkingtoward the Bari canyonsystem.