Natural values of the Solitary Islands Marine Park - Marine Parks ...

6 Natural values of the Solitary Islands Marine ParkFigure 5.Deploying a hydrophonelistening station and a seatemperature logger.Figure 6.An example of dailyvariation in seatemperature (NorthSolitary Island 8/3/02 and9/3/02), showing a 4.5 o Cdifference in less than24 hours, for temperaterecorded every 30 minutes.Currents vary on a range of temporal and spatial scales. Fluctuations over a few daysto weeks occur in response to the passage of weather systems, with water circulationin sheltered inshore waters often dominated by tides and local winds. Broader regionalfluctuations over months occur in response to seasonal and large-scale changes inoceanography. These changes are superimposed on longer-term cycles such as ElNino, or on decadal-scale cycles.There is considerable variation in the exposure of the coastline to swells in some areas,due to its complex shape and the presence of shallow offshore reefs. The obliqueaction of predominant southerly swells hitting the coast can also set up a northwardsweep around the headlands and along the beaches. This current is responsible fortransporting sediment northward along the northern NSW coast.Based on long-term data collected from three Waverider buoys located offshore innorthern NSW, there is little variation in mean monthly wave height across the year,with the highest mean wave height occurring in March (1.8 metres at Byron Bay)and the lowest in December (1.4 metres at CoffsHarbour). However, large waves over 4 metres highare more common in winter, with wave directionusually from the south-east through to the east.Occasionally, a north-east swell can result fromintense low pressure systems forming locally in theCoral Sea (Figure 7).Tides are semi-diurnal, with a maximum tidal rangeof 2 metres (Middleton 1996). Low tides of lessthan 0.3 metres generally occur during night-timein winter and during the afternoon in summer(Figure 8).