Seasonal Almanac

Minor heat: crickets come into walls (2 of 5)

January 12th, 2009

Minor heat 7 of 15When we saw our neighbour, Sarah Miller, on Saturday night, she told us that the day’s high tide swept her out of the Austinmer’s tidal pool onto the beach. Rather amazed by this event and having difficulty visualising how waves in the pool could be that high, I was very curious to see how this could have occurred. She told us that a ‘king tide’ was forecasted for today at 9.57am.

Spring tides occur around twice a month at the times of new and full moons. This is the time when the moon and the sun align in such a way that increases their gravitational pull on the Earth’s body of water. Exceptionally high tides peak twice a year, they are known as the summer king tide and the winter king tide, with the latter ususally occuring after night fall. Tides in general can vary from 2 to 3 cm in the Mediterranean to 15 m in Nova Scotia (Derby’s macrotide at 11.8 m in north-west Australia came second in the world). The variation is due to a number of factors including the shape of the land and surrounding ocean depth.

Today’s king tide was said to be at the peak of a 18.6 years cycle and much is made of it by the CSIRO and the media. As I found out subsequently, the public was called by the NSW government and local councils to photograph along the NSW coast to help us prepare for rising sea levels in the future. The excitement though was somewhat dampend by the high-pressure system in the region, apparently pushing down on the bulging water. But I can see how Sarah could have been swept out of the pool.

3 Responses to “Minor heat: crickets come into walls (2 of 5)”

  1. 1 Louise
    January 12th, 2009 at 9:53 pm

    Hey Jo they were discussing the king tide at the museum today and talking about how it made it up to the dolphins on Endeavour. They were all planning to go and check out the neap tide this avo also. When I next looked at Endeavour there were two blokes in the water bobbing about still managing to look official but very pleased with themselves while the rest of us stood around myself feeling very very jealous and others declaiming their lunacy for braving Darling Harbour jelly fish and sharks (never seen one of those in here, nor any other fish life beyond white glooby jellies). Back to the king tide – I struggled to identify the dolphins – they must be very high on the side of Endeavour as I gathered this was something noteworthy. Made me curious about why the vessel doesn’t just ride with the tide … I must follow that up. I will miss the boats there, they are very beautiful, somehow very dainty in that very commercial setting of the Darling Harbour basin.

  2. 2 jolaw
    January 12th, 2009 at 10:13 pm

    Hi Louise, what a nice story from the Australian National Maritime Museum! Are there waves in the harbour? Or does the water just rise with the tides? I wonder how they fared at the Aquarium where some displays are open to the harbour…

    We just pod-casted one of Hindsights’ programs (Radio National) on Captain Cook’s expedition near the Antartic – also lunacy! But what adventurous stuff! I guess that’s why there is so much romance attached to the maritime.

  3. 3 Louise
    January 14th, 2009 at 1:14 am

    Hello Jo

    There is often swell but there are not usually actual waves. The swell is a very big problem for the little boats. I gather the jet cats are the main culprit as their wake somehow rolls along the sea floor and takes a distance greater than the width of Sydney Harbour to disperse to a level where they don’t cause erosion – I don’t really understand this but I gather this is the general description of it – could also be factually wrong re jet cats but it’s a particular type of ferry.