Coral, climate change, storm surges and #CycloneDebbie – @takvera

March 26, 2017 Leave a Comment
John Englart

John Englart

Citizen journalist at No Fibs
John Englart has always had a strong social and environmental focus and over the past 10 years climate change science, climate policy and climate protest have become an increasingly important and primary focus of his work as a citizen journalist.
John Englart

@takvera

- 20 mins ago
John Englart
I am involved in various Moreland-based community groups including Sustainable Fawkner where I blog on local and sustainability issues, Climate Action Moreland and Moreland Bicycle Users Group. I am also a member of Friends of the Earth, off and on, since 1976, and wrote the contribution on the Rides Against Uranium in the 1970s for the Friends of the Earth Australia book to mark the 30-year anniversary of FoE – 30 Years of Creative Resistance.

Cyclone Debbie off Queensland. Image by BOM from Himawari satellite

Tropical Cyclone Debbie is forecast to cross Central Queensland coast on Tuesday morning as a Category 4 Severe tropical cyclone. It will bring destructive winds greater than 200km per hour plus a storm surge with a king tide innundating low lying coastal properties, and torrential rain causing flooding. It is also cooling sections of the Great Barrier Reef reducing coral bleaching from an extensive and long lasting marine heatwave.

Tropical Cyclone Debbie draws heat from the unusually warm waters of the Coral Sea. This will help it increase in intensity to achieve possibly Category 4, and an outside chance as a Category 5 severe tropical cyclone before it strikes land.

It is the first tropical cyclone to strike the north Queensland coast since Cyclone Nathan in March 2015. Although it may not be as strong, it is being compared in size and extent to the Category 5 cyclone Yasi from 2011.

The destructive winds and storm surge may wreck havoc on low lying coastal areas when the cyclone comes ashore.

The cyclone brings substantial cloud cover to the region and helps to cool the general water temperature. It may thus help limit coral bleaching, which involves the expulsion of Zooxanthellae by the coral polyps when the waters get too warm. For those coral reefs in the southern reef system already suffering mild coral bleaching, it can help them recover more quickly. But for many corals the cyclone cooling the waters may already be too little, too late.

Great Barrier Reef corals have again been subjected to extensive stress by elevated water temperatures in a marine heatwave. While the 2016 extensive coral bleaching was related to elevated temperatures from an El Nino event. Water temperatures have remained anomalously high this year while the El Nino Southern Oscillation (ENSO) was in a neutral phase.

At one stage tropical cyclones were seen as a primarily destructive force for coral reefs, but now they are seen as also bringing cloud cover and suppressing sea surface temperatures a little and preventing greater coral bleaching.

Cyclone Debbie isn’t the embodiment of climate change. But it is occurring in a climate changed world.

Tropical Cyclones are likely to reduce in frequency, but the numbers of high intensity cyclones are likely to increase. Warmer ocean waters can contribute to the stronger cyclone intensity.

Higher atmospheric temperatures mean that more water vapour can be held aloft and therefore dumped causing high torrential rainfalls and local flash flooding and landslides. Indeed, the Bureau of Meteorology have issued a flood warning for Cyclone Debbie: “Heavy rainfall associated with Tropical Cyclone Debbie is expected to result in widespread daily totals of up to 200 mm from Monday. Isolated daily totals of up to 400 mm are possible particularly in the coastal catchments in the Flood Watch area.”

Storm surges become more dangerous as they are added to a mean sea surface level already increased by sea level rise.

The 2011 Intergovernmental Panel on Climate Change (IPCC) Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX) predicted that with Tropical Cyclones, Intensity may increase but frequency may stay the same or even decrease. Wind speeds are likely to increase, although perhaps not in all ocean basins. Medium confidence in a projected poleward shift of extra-tropical storm tracks, and a reduction in the average number of extra-tropical cyclones. (I blogged about this report here)

For Cyclone Debbie coastal warnings from St Lawrence to Cape Tribulation have been issued, but the cyclone path is presently forecast to impact between Hamilton Island and Cardwell with the city of Townsville also being in the impact zone.

Residents are being urged to put in place their emergency plans. The Premier has announced that 25 Schools in the affected area will be closed on Monday.

Already some supermarkets have seen their shelves of bottled water, bread and UHT milk denuded.

Bruce Gunn, Bureau of Meteorology (BoM) deputy regional director compared the storm with Cyclone Yasi from 2011, according to Channel 9 News, “Queensland hasn’t seen a coastal crossing for a couple of years now since Marcia or Nathan in 2015 but I think you could probably say that Debbie’s the most significant tropical cyclone since Yasi,” he said. “Not so much because of its intensity … mostly because of its size and extent. It’s quite a sizable system.”

Yasi caused $800 million in property damage in 2011.

Storm surge

Cyclone Debbie will bring a storm surge, which will be on top of the King tide about to happen. Many low level coastal areas will be impacted by this storm surge with the various Council’s publishing maps of affected areas and urging evacuation of those living in low lying coastal areas.

It’s a new moon on 28th March which accentuates ocean tides. These are forecast tidal figures from the Bureau of Meteorology website:

Tides along Queensland coast. 28 March 2017 is a new moon king tide
28/03/17Mackay outer harbourLaguna KeysAbbot PointTownsville
LOW04:560.55 m05:22 0.44 m03:34 0.62 m02:41 0.69 m
HIGH10:545.93 m11:29 5.29 m09:31 3.10 m08:55 3.67 m
LOW17:220.45 m17:47 0.32 m16:04 0.61 m15:23 0.75 m
HIGH23:205.76 m23:53 5.13 m21:58 2.91 m21:20 3.51 m

Here is the sea level anomaly projected for Monday 27 March for Queensland coast by the Bureau of Meteorology:

Forecast path of Cyclone Debbie (Sunday afternoon)

Townsville:

Burdekin region:

Whitsunday:

Mackay:

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