Solving dense shelf water cascading with a high-resolution ocean reanalysis

Abstract. Dense shelf water cascading (DSWC) is an oceanographic process occurring when dense shelf water overflows the shelf edge downslope towards the deep sea. Monitored in the Northwestern Mediterranean by moorings since 1993 in the Lacaze-Duthiers Canyon and since 2003 in the Cap de Creus Canyon, numerical modeling with reanalysis extends this timeline further into the past. This study investigates a regional reanalysis (1987 – 2021) validated against mooring observations at 750–1000 m depth. The reanalysis successfully reproduces observed Intense DSWC (IDSWC) events from 1999, 2000, 2005, 2006, 2012, 2013, and 2018, while identifying one previously unreported event in 1987, and detecting no IDSWC between 1988 and 1998. The reanalysis effectively matches 84 % of observed IDSWC days within the same week and 56 % on the exact date. Instead of assimilating IDSWC events from mooring observations to resolve the cascading process, the model relies solely on the seawater density on the shelf. Reanalysis data have revealed the seawater properties along the canyon that caused IDSWC and can be used to find other unreported cascading events elsewhere.