Extreme oceanic events David Griffin CSIRO Marine and Atmospheric Research
Jan 03, 2016
Special thanks to
• Madeleine Cahill• George Cresswell and Jason Middleton• John Wilkin and Alan Pearce• Peter Campbell, Jason Waring, • Kim Badcock (and the whole remote sensing group)• Jim Mansbridge• The Bluelink and IMOS communities (many great people)• Peter Thompson, referees and the panel
• Event was extreme but not unprecedented• Shift focus to the virus• Exposed ill-preparedness for addressing urgent questions• Assembling data took too long• Available data were too few• Too hard to know ‘how anomalous’ various observations were• Nevertheless, I think we got it right• BTW, the next comparable upwelling was not til 2010:
Highest-ever sea level at Fremantle, 2pm WST:
3h period seiche (Molloy, 2001)
MSL
surge
tide
Leeuwin
Cockburn Sound.Highest sea level: 2pm WST 10 June 2012:
Photo Credit: Steve Brooks, PerthWeatherLivePhoto: Steve Brooks, Perth Weather Live
Insert presentation title
Median energy flux of ocean currents
0 Median non-tidal current speed 0.8 (m/s)
Insert presentation title
Median energy flux of ocean currents
0 Median non-tidal current speed 0.8 (m/s)
Cyclonic Eddy(Low sealevel)
Is it real? Yes, see drifter.
Is it extraordinary?Lets look at some history
Maximum (in 1994-2011) gridded altimetric (+ filtered tidegauge) sea level anomaly:
+1m
SLA
-1m
wide range:
0.3m
to
1.1m
99th percentile anomaly (exceeded 1% of time) - the max is 30% higher than this
+1m
SLA
-1m
0.2m
0.7m
Maximum anomaly map again.highest highs are south of the lowest lows
+1m
SLA
-1m
Lowest low was here
Highest highIs here
That high sea level all along the Qld-NSW coast was not a ‘storm surge’
• Coastal sea level was very high. Anomaly of nearshore current was zero. Odd situation – still needs investigation.
• Lets now go back to 16 Jan then step forward.
Discussion
• Marine science has tended to focus on the ‘normal’ behaviour of the ocean
• But observing systems are now adequate for us to also focus on the rare occasions when something extreme happens
• Some events have obvious societal impacts, e.g. beach erosion, coastal flooding, coral bleaching, fish kills, oil rig failures
• Many do not – but may – e.g. chlor-a blooms and deserts• Extreme events pose a challenge to observing system
design, quality control of data, and data interpretation• I think the effort is warranted