Jennifer Marohasy

a forum for the discussion of issues concerning the natural environment

More Ocean Temperature Data, and Explanations – One Tree Island

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According to the ‘AIMS Reef Snapshot Summer 2023-24’ report, the southern Great Barrier Reef is most at risk of coral bleaching, with Great Keppel Island one of the highest risk areas.  I will be over at the island this weekend.  (Subscribe for my weekly emails to be sure to see my photographs from under-the-water, CLICK HERE.)

Since posting some AIMS water temperature data for the nearby Square Rocks (CLICK HERE), I’ve been looking for some other more southern water temperature data that is relatively up-to-date.

The feature image is AIMS water temperature data as recorded at One Tree Island from 2.3 metres depth from March 25, 2013, to February 4, 2024.  The time series is mostly complete showing 11 consecutive summers.  I’m confident this chart has caught the peak warmth for this last summer, 2023-2024, and it is from the southern Great Barrier Reef.

Again, this AIMS water temperature data does NOT show this last summer to be exceptionally warm.  This last summer appears to be about as warm as the summer of 2019-2020.   I know there was coral bleaching at the nearby Heron Island early in 2020.  The bleaching was severe, but with full recovery within a few months.

I’ve been in touch with AIMS regarding how this data is measured.  I’m very grateful for the reply from Suzannah this afternoon explaining that the temperature is recorded every 10 minutes continuously.   The solid blue/green/orange line generated by their automated charting app represents the average for the week, with the light shading showing the upper and lower range values for the weekly average.

Water temperature data from three different sensors measuring every 10 minutes, continuously, at One Tree Island. You can download this data here: https://apps.aims.gov.au/ts-explorer/?source=15215:Temp%20logger&fromDate=2013-03-25T00:00:00&thruDate=2023-02-04T00:00:00

Given these measurements represent a continuous average, the data could be used to generate accumulated ‘Degree Heating Days’.  However, it would appear from the ‘AIMS Reef Snapshot Summer 2023-24’ report that the ‘Heat Maps’ are instead a Bureau of Meteorology product and I’m guessing based on homogenised satellite data.   I am hoping to receive confirmation from AIMS about this on Monday.

To be clear, the high-quality, location specific, temperature time series, of actual underwater temperatures that I have been posting in recent blog posts (ESPECIALLY MYRMIDON CLICK HERE), are NOT used to generate the heat maps that are being promoted to suggest the Great Barrier Reef is bleaching from elevated sea temperatures.

Just today my mother sent me a clipping from the Cairns Post with the headline ‘Great Barrier Reef Grief’ and my husband tells me the BBC is reporting that ‘75% of the Great Barrier Reef is being lost to bleaching’ with both media outlets blaming global warming.    As far as I can tell the AIMS location specific data is being ignored, with a preference for contrived Bureau modelling while the bleaching percentages quoted are based on aerial surveys from out an airplane window at 150 metres altitude.

We could do so much better.

A photograph taken in November 2021 under-the-water at Heron Island, not far from One Tree Island. I was on that dive, and the photograph was taken by Stuart Ireland. We have placed a colour chart in the foreground for accurate colour correction. You can see many pale coloured Acropora, and if you look carefully the stems of the branching corals are a bit darker and replete with zooxanthellae.

We incorporated quite a bit of footage from that trip to Heron Island into a film we made, entitled ‘Bleached Colourful’… CLICK HERE to watch the film, and to learn more about how corals change colour, and how they are sometimes more colourful when they are stressed.

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Comments

  1. Christopher Game says

    Is there some way for you to try to correlate local water temperature with local coral growth or health on a week-to-week time scale? Does that question make sense? Has it already been done?

    Is there evidence relating coral bleaching to water temperature?

  3. Christopher Game says

    Dear Kevin, For me, the question is how do you explain the warming trend? I guess Jen may have difficulty explaining it, because most such change is difficult to explain. But I guess, Kevin, that you have no such difficulty? I can easily guess, though I have to wait to find out, what is your actual explanation. The burden of proof, Kevin, is on you, not on Jen.

  4. Avatar photojennifer says

    Thanks Kevin, for all the plotting.
    There are cycles within cycles. The AIMS data can give us an idea of the seasons and how hot and cold it regularly gets.
    If you want to understand the longer series you need longer data sets.
    I’ve done some poking around here, https://jennifermarohasy.com/2019/08/lady-elliot-just-a-hot-flush/
    That shows it was cooling to about 1950, and then warming followed. There are 60 year cycles associated with gravitation effects of Jupiter and Saturn.
    Then there are the longer cycles that span thousands of years. I’ve done some poking about there as well, in my GeoResJ paper with John Abbot.
    And of course there are the 100,000 years cycles with some information here: https://jennifermarohasy.com/2023/11/political-and-natural-hazards-arc-part-3/ Actually the 100,000 year cycle chart is here: https://jennifermarohasy.com/2023/11/in-denial-about-the-science-part-2-arc-in-london/