Dense shelf water cascades along the north-west Australian continental shelf

Research output: Chapter in Book/Conference paperConference paper

Abstract

High evaporation during the summer and cooling during winter
along the coastal regions of the Australian north-west shelf
(NWS) results in a cross-shelf density gradient. This drives a
gravitational circulation with the offshore transport of higher
density water along the sea bed, defined as Dense Shelf Water
Cascades (DSWC). Ocean glider data available from the
Integrated Marine Observing System (IMOS) were used to
measure cross-shelf density gradients under varying wind and
tide conditions along the Kimberley and Pilbara regions of the
North-West Australian shelf. Analysis of 41 transects from 26
missions of high spatial and temporal resolution data collected
between 2011 and 2015 confirmed that DSWC occur on a regular
basis during the winter months, mainly due to cooling of the
coastal waters that were pre-conditioned with higher salinity
resulting from evaporation during the summer months. The crossshelf
transects indicated that both temperature and salinity
contributed to the dense water formation. The dense water flow
along the sea bed was identified to depths of up to 150m. The
strongest density gradient calculated in the Kimberley was 5.123
x 10-6 kgm-4, whilst for Pilbara it was 14.23 x 10-6 kgm-4. The
temporal variability and controlling mechanisms of the DSWC
were investigated using data from current meter moorings
deployed on shelf regions of the Kimberley and Pilbara.
Although these two regions are macro-tidal and are subject to
wind mixing, the vertical temperature stratification and monthly
mean cross-shore velocity profiles indicated the presence of
cascades during winter months. It is shown that even in the
presence of high tidal mixing DSWCs persist due to the strength
of the cross-shelf density gradient.
Original languageEnglish
Title of host publicationProceedings of the 20th Australasian Fluid Mechanics Conference
EditorsGreg Ivey, Nicole Jones, Tongming Zhou
PublisherAustralasian Fluid Mechanics Society
ISBN (Electronic)978-1-74052-377-6
Publication statusPublished - 2016
Event20th Australasian Fluid Mechanics Conference - University of Western Australia, Perth, Australia
Duration: 5 Dec 20168 Dec 2016
Conference number: 20
http://www.afms.org.au/20AFMC/

Conference

Conference20th Australasian Fluid Mechanics Conference
Abbreviated titleARMC
CountryAustralia
CityPerth
Period5/12/168/12/16
Internet address

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Cite this

Mahjabin, T., Bahmanpour, M. H., Pattiaratchi, C., Hetzel, Y., Wijeratne, E. M. S., & Steinberg, C. (2016). Dense shelf water cascades along the north-west Australian continental shelf. In G. Ivey, N. Jones, & T. Zhou (Eds.), Proceedings of the 20th Australasian Fluid Mechanics Conference Australasian Fluid Mechanics Society.