Title :
AUV observations of mixing in the tidal outflow from a Scottish sea loch
Author :
Boyd, T. ; Inall, M. ; Dumont, E. ; Griffiths, C.
Author_Institution :
Scottish Assoc. for Marine Sci., Scottish Marine Inst., Oban, UK
Abstract :
Freshwater outflows from estuarine systems carry nutrients, sediments, larvae and other materials into the coastal ocean where they mix into ambient ocean water. Loch Etive is one such estuary on the west coast of Scotland that is fed by a large rainfall catchment area, and from which the outflow is strongly modulated on a tidal basis. Freshwater leaves the loch on the ebbing tide in a pulse released into the coastal ocean as a thin layer, the leading edge of which develops into an undular bore or a train of internal solitary waves with strong mixing and associated entrainment. A Hydroid 600 m depth-rated AUV equipped with a forward-mounted microstructure sensing package has been used in conjunction with moored measurements to study the dynamics of thin freshwater layers that are regularly released into the coastal ocean. During observations conducted in winter 2009 and spring 2010 we observed turbulent bores and internal solitary waves in Ardmucknish Bay, near the entrance to Loch Etive. The passage of the bores and internal solitary waves of depression were associated with downward vertical movement of near-surface water and turbulent mixing that was enhanced above background by over 2 orders of magnitude.
Keywords :
mixing; ocean waves; oceanographic regions; rain; remotely operated vehicles; sediments; stratified flow; tides; underwater vehicles; Hydroid 600m depth-rated AUV; Loch Etive; Scotland; Scottish sea loch; ambient ocean water; coastal ocean; downward vertical movement; ebbing tide; entrainment; estuarine systems; forward-mounted microstructure sensing package; freshwater outflows; internal solitary waves; larvae; near-surface water; nutrients; rainfall catchment area; sediments; strong mixing; thin freshwater layers; tidal basis; tidal outflow; turbulent bores; turbulent mixing; undular bore; Leg; Microstructure; Oceans; Pollution measurement; Sea measurements; Sensors; Vehicles;
Conference_Titel :
Autonomous Underwater Vehicles (AUV), 2010 IEEE/OES
Conference_Location :
Monterey, CA
Print_ISBN :
978-1-61284-980-5
DOI :
10.1109/AUV.2010.5779670