Coral Bleaching & The Reef

Bleaching events result from extended periods of calm weather during which mixing from wave action ceases and surface water becomes exceptionally warm. Such warming is especially marked in very shallow water such as on reef flats. At the same time the absence of waves also eliminates the wave driven currents that normally flush the reef top. Bleaching conditions require at least a week or more of calm weather to develop and this may happen every few years, only once in a century, or never, depending on geographic location. On the outer GBR it is uncommon due to ocean swell and currents even in calm weather. In the mid-shelf and inshore areas it is much more common due to the absence of swell and reduced currents.