Widespread Coral Bleaching Strikes Great Barrier Reef Again in 2017

During early 2017, the region over Australia’s Great Barrier Reef (GBR) experienced its hottest summer atmospheric temperatures on record. Peak water temperatures lag peak air temperatures by about a month. But already, sections of one of the world’s most vital marine sanctuaries are experiencing bleaching and disease. Worryingly, bleaching and heat stress is expanding over the reef at a faster rate than at the same time last year.

Coral Bleaching Great Barrier Reef

(The Great Barrier Reef is already experiencing extensive bleaching in 2017. With warmer waters headed toward the reef over the coming weeks, researchers fear that this year’s coral mortality event could match or exceed 2016’s severe damage and loss. Image source: Commons.)

A Precious Global Treasure Under Threat

During 2016, the GBR experienced its worst coral bleaching event on record. This severe event followed two years (2014-2015) in which the reef saw less widespread bleaching. A strong El Nino combined with the highest global temperatures ever measured to produce ocean conditions that were too hot to support living corals and many regions saw bleaching and high mortality. In the reef’s northern sections, more than 2/3 of the corals bleached and died out.

Scientists who’d long warned that global warming would put the fate of the great reef at risk, issued an alarm and a call for action. Global temperatures had now reached a threshold that threatened to put Australia’s natural wonder at risk with far greater frequency than ever before. Scientists warned that by the 2030s, ocean temperatures would be warm enough to produce a bleaching event similar to the 2016 die-off every 2-3 years. A separate study indicated that the reef could experience severe coral bleaching through at least 2040 (and well beyond if the world continued to burn fossil fuels and to warm up at such rapid rates).


(Under human-forced warming the frequency of coral bleaching events and reef mortality is expected to dramatically increase over the coming decades. However, with global temperatures now 1.2 C warmer than 1880s levels, the amount of stress to corals is already remarkably high. Image source: The World Resources Institute.)

Some questioned if the reef could survive such a severe onslaught of global heat brought about by human fossil fuel emissions. Others pointing out that, unless those heat-trapping emissions were dramatically curbed, warming alone had the potential to kill off most of the reef within the next 20 years.

More Coral Bleaching as Ocean Near GBR Fails to Cool in 2017

Nearer-term concerns were also raised that risks to the reef remained high in the present abnormally warm ocean environment. For as 2017 followed 2016, the global coral bleaching event that began in 2014, and that had already claimed the lives of so many of the world’s corals, remained in force.

During the winter of 2016-2017, a weak La Nina event (NOAA) brought some hope that the GBR might get a chance to recover from this most recent spate of extreme ocean warmth. However, by February, La Nina (which was never strong enough to be officially recorded by Australia’s BoM) had faded even as indicators pointed toward a new El Nino beginning to gather. Meanwhile, global atmospheric carbon continued to increase — hitting 490 CO2e by late 2016.


(NOAA predicts another bad year for the world’s corals as a new El Nino threatens to emerge and as global temperatures remain near record highs set in 2016. Image source: NOAA.)

Ocean temperatures in the 30 C + range that typically produce bleaching began to spread over parts of the reef. These conditions were warmer than during the same period of 2016 — raising the awful potential that impacts to the reef during 2017 could be as bad or even worse than last year’s record event.

Worse than 2016 So Far

As of this week, new reports of bleaching were starting to emerge in six GBR reefs in the region of Mission Beach. According to Queensland’s Environment Minister Steve Miles:

“Queensland has just experienced its hottest summer on record and above average temperatures are predicted until the end of March. Some corals were still under stress from last year’s bleaching event and that was exacerbated by a warmer than average winter. The next four weeks will be critical and we can only hope that water temperatures will be cooler than the forecast.’’

The six reefs in question, stretching from Cairns to Townsville, already showed 60 percent bleaching — primarily among the more heat-sensitive corals. And the extent of bleaching was more advanced than during the same time in 2016. Over the coming weeks, the pulse of warm water is expected to spread, putting still more corals at risk as the unprecedented ocean heat moves southward through the marine sanctuary.

So it appears that the GBR is in for another rough summer — one with the potential to see impacts similar to or exceeding those of 2016. Moreover, with global oceans continuing to warm, with world governments still dragging heels on carbon emissions reductions, and with Trump and others vowing to reinvigorate coal, the plight of the GBR is now quite dire.



Great Barrier Reef Faces New Coral Bleaching Threat

Ecologists Steel For More Coral Bleaching on Great Barrier Reef

Large Scale Projections of Coral Reef Futures

Reef Authority Reveals More Coral Bleaching

Global Coral Bleaching Event

The World Resources Institute


Hat tip to Keith

The Permanent Global Coral Bleaching Event

Despite La Nina, Ocean surfaces have not cooled enough to end the worst global coral bleaching event on record. What this means is that many reefs, including the Great Barrier Reef, are again under a rising risk of bleaching and mortality for the coming months. This is unheard of. Never before has a mass coral bleaching event lasted for so long or extended through the period of natural variability related ocean surface cooling called La Nina. Perhaps more ominously, the global coral bleaching and die off that began in 2014 may now be a practically permanent ocean feature of the presently destabilized world climate system.

Cool La Nina is Over

According to NOAA, the periodic cooling of ocean surfaces in the Pacific called La Nina is now over. And since La Nina brings with it a variable related low point of broader Earth surface temperatures, after a few months lag, we can expect the globe to start to warm up again.


(The above map shows sea surface temperature anomalies in the Pacific Ocean on February 9 of 2017. Presently SSTs over the entire Pacific range from about -1.5 C below average to +5 C above average. And as you can see, the Ocean is considerably warmer than normal, despite La Nina. Over the next 1-2 years, this is likely the coolest the Pacific will get. In just one decade’s time, under human-forced warming, it will take a very strong La Nina and a strongly negative Pacific Decadal Oscillation to produce similar sea surface temperatures. Image source: Earth Nullschool.)

Problem is, the Earth is still ridiculously warm, despite La Nina. Temperatures, driven inexorably higher by fossil fuel burning, have probably bottomed out at about 1 degrees Celsius hotter than 1880s averages during December, January and February of 2016-2017.

What this means is that the likely range for annual global temperatures over the next 5 years will be about 1 to 1.3 C above 1880s averages. These readings are so high (the warmest in 115,000 years) and have risen so much, in such a geologically short span of time, that many of the world’s more sensitive species are now being pushed out of their habitats and are undergoing considerable heat-related mortality events.

Great Barrier Reef Under Threat From Bleaching for Second Year in a Row

Perhaps the most obvious of these horrendous fossil-fuel burning spurred instances is the global coral bleaching event that began in 2014. More ominously, it now appears that surface temperatures in the range of 1 C hotter than 1880s and above may well be enough to push the world into a permanent or near-permanent state of global coral bleaching and mortality. What this means is that each year, from now on, there is a considerable risk of widespread coral bleaching. It also means that reefs impacted by bleaching will tend to have shorter cool periods in which to recover.


(NOAA’s 60 percent certainty map shows very widespread coral bleaching expected over the next few months. Presently, bleaching is predicted for the region of the Great Barrier Reef. But other reef systems [see below] fall under higher risks for considerable reef mortality events in the current forecast. Image source: NOAA.)

For February through May of 2017, very warm and warming sea surface temperatures in the Southern Hemisphere are expected to produce extraordinarily widespread risks of coral bleaching. Many areas are predicted to see the highest coral bleaching alert level NOAA has a measure for.

According to NOAA:

Multiple coral reef regions are already experiencing Alert Level 1 bleaching stress (associated with significant coral bleaching). Alert Level 2 bleaching stress (associated with widespread coral bleaching and significant mortality) is expected in the Northern Cook Islands, Southern Cook Islands, the Samoas, Wallis & Futuna, Northern Tonga, Southern Tonga, the Society Archipelago, and the Austral Islands in the next 1-4 weeks. Alert Level 1 bleaching conditions are also expected in the Tuamotu Archipelago in the next 1-4 weeks and in Tuvalu in the next 5-8 weeks.

The prediction map also includes the potential for high alert levels (level 1) for sections of the Great Barrier Reef which last year experienced its worst coral bleaching event on record. Needless to say, a second year of bleaching would be a devastating additional blow to a critical ocean life support system and one of Australia’s priceless national treasures.


Global Coral Bleaching Event Status

Earth Nullschool

NOAA: La Nina is Over

Hat tip to George Hayduke


Why the Global Coral Bleaching Event That Began in 2014 May Just Keep Going and Going

From October of 2014 through June of 2016, the world was in the grips of a powerful El Nino. And throughout this event, the oceans spewed back some of the massive volume of heat they’ve been accumulating in their depths due to global warming. As a result, atmospheric and ocean surface temperatures hit new record highs. And during 2016, global surface temperatures will likely average 1.2 C hotter than 1880s levels. This amount of warming is as considerable as it is harmful.


(A global coral bleaching event that began in 2014 continues. It is the longest coral bleaching event on record. But unless oceans somehow cool off, it won’t really end. With only a weak La Nina emerging following a strong El Nino and a record spike in global temperatures, there is some risk that this ongoing event will ebb and flare on a nearly indefinite basis. Continued fossil fuel burning, meanwhile, will continue to add heat to the global climate system — presenting worsening medium and long term bleaching pressure for corals. Image source: Coral Reef Watch.)

The Worst Global Coral Bleaching Event Ever Recorded… 

This new record spike in global surface temperatures set off the worst coral bleaching event ever recorded. Around the world, reef systems came under severe stress as sea surface and near surface temperatures exceeded 28-30 degrees Celsius.

Among the hardest hit regions were the reefs of Kiribati. There, sea surface temperatures hit up to 31.4 C on an extended basis. Such hot waters are now expected to have wiped out all but 1 to 5 percent of Kiribati’s living corals. So, for all practical purposes, the reefs of that island republic have been wiped out.

Overall, the event was very wide ranging — impacting corals throughout the Pacific, Atlantic, and Indian Oceans as well as in the Persian Gulf, Mediterranean, and Red Sea. As an example, 95 percent of corals in US territories from Florida to the Gulf of Mexico, Caribbean, and Pacific experienced some level of bleaching.


(A weak La Nina has probably already cooled ocean surfaces as much as they will be cooled during 2016 and 2017. But despite this cooling, ocean near-surface waters are still too hot for corals in many places. Relative, if mild, ocean surface warming should occur as ENSO is predicted to shift into neutral status. If coral bleaching is ongoing through La Nina, then it is unlikely to cease as the global ocean starts to warm again. Global sea surface temperature anomaly image source: Earth Nullschool.)

In Australia, the Great Barrier Reef (GBR) also saw its worst bleaching event on record. There, 93 percent of corals are reported to have experienced bleaching. Meanwhile, about 50 percent of corals have died in the northern section of the GBR. In the media, a controversy has raged over whether or not this event is the start of the great reef’s swansong. To be clear, the GBR was not killed off by the most recent large bleaching event. But it was dealt a very severe blow. With the world continuing to warm as fossil fuel burning remains ongoing, a similar blow could occur as soon as the next El Nino or the one after. And the story for many of the world’s remaining reefs could well be the same.

…Is Still Ongoing…

For after about two years now, and as the world has settled into the periodic natural cooling of ocean surfaces called La Nina, the global coral bleaching event that has so damaged the vital species that build the world’s reefs is still ongoing. Though diminished, and as ocean surface heat backed off during late 2016, NOAA has still identified numerous regions that are high risk for coral bleaching through at least February.


The austral summer is expected to bring bleaching over far-flung regions encircling the southern part of the globe. Thankfully, most of the GBR is only under a bleaching watch for now. But bleaching warnings and alerts abound and, unfortunately, many reefs are likely to see continued die-offs even after El Nino has long since faded.

… And May Just, For all Practical Purposes, Continue

As the current La Nina is rather weak, and as it is predicted to shallow into an ENSO neutral state by spring, it appears that sea surface temperatures may be in the process of bottoming out. Global fossil fuel emissions, meanwhile, continue to add heat to the ocean system. As a result, the coral bleaching pressure that we are seeing during the period of November 2016 through February of 2017, unless we see a resurgence to a stronger La Nina event over the next year or two, could be the minimum we will see over the coming years. And if that is the case, then the coral bleaching event that hasn’t ended for the past two years may not really end at all.


NOAA Coral Reef Watch

NOAA El Nino

Earth Nullschool

Dr Gavin Schmidt of NASA GISS

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