Higher Tides

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Recently the NSW media was, well, awash with news articles on the high tides being experienced along the NSW coast. What caused the higher tides and  how do they compare with historic tide levels?

A couple of news articles from 6 December 2017 in the Sydney Morning Herald and MSN describing the impact of higher than usual tides.

While it's entirely predictable that some of the highest tides of the year will occur around Christmas time, what wasn't predictable was the super elevation of tide levels due to the coincidence of the high astronomical tides with a storm surge, a relatively intense low pressure system and a possible coastal trapped wave generated by cold fronts moving through Bass Strait.  

Yes it's complex....and also points to the potential creeping impact of rising sea levels in a warming world.

Check out some of the images from the NSW Central Coast captured by Phil Watson from the NSW Office of Environment and Heritage 

For the record, the tides at Fort Denison in Sydney Harbour on the morning of 6/12/17 peaked at 10.54 am at 2.28m ISLW (approx. 27cm above the predicted tide of 2.01 ISLW). According to published information for the tide gauge, this level is fourth highest level ever recorded at Fort Denison. Recorded water levels published in Watson and Lord (2008) are listed below

Maximum Recorded Water Levels ISLW (metres) / AHD (metres) / Date (time)
2.40m   25 May 1974 (2300 hrs)
2.35m   27 April 1990 (2200 hrs)
2.32m   10 June 1956 (2100 hrs)

2.28m    6 December 2017 (1054 hrs)
2.27m   30 June 1984 (2200 hrs)
2.27m   19 August 2001 (2000 hrs)