Not enough time for recovery
Coral bleaching occurs when stressful conditions result in the expulsion of the algal partner from the coral.
Before anthropogenic climate warming, such events were relatively rare, allowing for recovery of the reef between events.
Hughes et al. looked at 100 reefs globally and found that the average interval between bleaching events is now less than half what it was before.
Such narrow recovery windows do not allow for full recovery.
Furthermore, warming events such as El Niño are warmer than previously, as are general ocean conditions.
Such changes are likely to make it more and more difficult for reefs to recover between stressful events.
Tropical reef systems are transitioning to a new era in which the interval between recurrent bouts of coral bleaching is too short for a full recovery of mature assemblages.
We analyzed bleaching records at 100 globally distributed reef locations from 1980 to 2016.
The median return time between pairs of severe bleaching events has diminished steadily since 1980 and is now only 6 years.
As global warming has progressed, tropical sea surface temperatures are warmer now during current La Niña conditions than they were during El Niño events three decades ago.
Consequently, as we transition to the Anthropocene, coral bleaching is occurring more frequently in all El Niño–Southern Oscillation phases, increasing the likelihood of annual bleaching in the coming decades.
Press link for more: Science Magazine
El Niño Alert
The ENSO Outlook is set at El Niño ALERT.
This means the chance of El Niño forming in 2018 is around 70%; triple the normal likelihood.
The tropical Pacific Ocean has warmed in recent weeks and is now just touching upon the El Niño threshold.
Latest observations and model outlooks suggest further warming is likely, with most models indicating a transition to El Niño in November remains likely.
El Niño ALERT is not a guarantee that El Niño will occur; it is an indication that most typical precursors of an event are in place.
While this would be late for an event to develop, it is not unprecedented.
Press link for more: BOM.GOV.AU
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