oceanography off western australia – what have we learnt in ......oceanography off western...
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Oceanography off Western Australia –what have we learnt in the first decade of
IMOS? Charitha Pattiaratchi
School of Civil, Environmental and Mining EngineeringThe UWA Oceans Institute
The University of Western Australia
Indeed, I think that as we go on piling measurements upon measurements, making one instrument after another more perfect to extend our knowledge, the sea will always continue to escape us
Belloc, The cruise of the Nona (in Pugh, 1987)
A scholar’s positive contribution is measured by the sum of the original data that they contribute. Hypotheses come and go but data remain.
Santiago Ramon y Cajal, 1897
Ningaloo Nino
Passive Acoustics: Perth Canyon
AATAMS: Ningaloo
Personnel: Ming Feng, Rob McCauley, Patrick Sears, Gary Kendrick, Julian Partridge, Lynnath Beckley, Steve Buchan, Nick D’Adamo, Nick Caputi, Sasha Gavrilov, David Antoine, Peter Thompson, Craig Steinberg, Richard Brinkman, Mark Meekan, Simone Cosoli
+ support staff, students + others
Emeritus: Jamie Oliver, Peter Rogers, Agi Gedeon, Merv Lynch, Anya Waite, Steve Blake, Alan Pearce
AUV–habitats
SRFME
WAMSI
Step Change ?
FranklinSouthern Surveyor
ozROMS (2000-2014)Australian Boundary Currents
Australian Boundary Currents
Holloway Current
Leeuwin Current
SICC
Results indicate that at least during the low wind conditions of the Southern Hemisphere autumn, a reasonably well-defined, south-westward coastal flow occurs along the shelf and shelf break. We propose to formalise the name of this autumn current over the North West Shelf as the Holloway Current, in honour of the pioneering work by the late Dr Peter Holloway.
Holloway Current
D’Adamo et al.:
Holloway Current
Seasonal winds/Sea level
Seasonal winds
Kronborg (2004)
Holloway Current
Geostrophic current anomaly- from Altimeter for April
Kimberley and Pilbara transects funded through WA State Govt co-investment in IMOS
Holloway Current: annual mean
Holloway Current inflow
~4 Sv
~2 Sv~2 Sv
Pilbara Transect: seasonal
Kimberley Transect : seasonal
WA Mean Sea level/LC Transport
Geostrophic Velocity fromAltimeter
Ocean Glider deployments
Dense shelf water cascade
Dense Shelf Water Cascade
Critical latitude and Resonance
An oscillation can be driven by an oscillating driving force; the frequency of the driving force may or may not be the same as the natural frequency of the system.
If the frequency is the same as the natural frequency, the amplitude can become quite large. This is called resonance.
In the ocean we have to take Earth’s rotation into account.
A parcel of water will rotate, time taken to complete a circle is the inertial period. At 30o N & S the inertial period is 24 hours.
24 hours is also the same period as the sea breeze !!
Simpson et al. 2002
Critical latitude and Resonance
Sea Breeze Cycle
Critical latitude
Critical latitude
Coffs Harbour
HF Radar surface currents
Ocean GlidersMoorings
ADCP, thermistorsShipborne Measurements
SatelliteOcean colour, SST
Multi-platform
Tea Leaf Paradox = Peddies ?
When you stir a cup of tea with tea leaves, where do the tea leaves usually end up?
Solved by Einstein in 1926.
When stirring, rotation is usually slower at the bottom. This creates a secondary flow where fluid rises in the center and falls at the edges. Tea leaves participate in this flow, but are too heavy to become lifted by the flow at the bottom, and so stay at the bottom center.
HF Radar coverage
Peddies: 16 August –Glider track
Density
Peddies: 16 August –Glider track
Locations of Peddies
Cyclonic 768 Anti-cyclonic 816
36 months of data
Eddies – strong currents
Eddies (>2 days)
12041359
Billow clouds
Shear mixing
Kelvin-Helmhotz Billows
Kelvin-Helmhotz Billows
Kelvin-Helmhotz Billows
West Australian Coast
Capes Current
Leeuwin/Capes interaction23 December 2013
Leeuwin/Capes interaction
Leeuwin/Capes interaction
Leeuwin/Capes interaction
Leeuwin/Capes interaction
Leeuwin/Capes interaction
0
10
20
30
40
50
60
70
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Leeuwin/Capes interaction
Leeuwin/Capes interaction
2013
Leeuwin/Capes interaction
Leeuwin/Capes interaction
Continental Shelf Waves
Tropical low
Narelle5-15 January 2013
Olwyn8-14 March 2015
Remote forcing from tropical cyclones generate sub-mesoscale eddies
Rottnest Swim
http://coastaloceanography.org/
Port to Pub swim
Acknowledgements
Sarath Wijeratne, Yasha Hetzel, Ivica Janekovic, Simone Casoli, Hrvoje Mihanovic
Mohammad Hadi Bahmanpour, Tanziha Mahjabin, Miaoju Chen, Jennifer Penton
Pawsey Supercomputing Centre