Sea surface temperature anomalies
QUESTION
Why do you all now insist using emotive and sensation grabing language by declaring a “Marine Heat Wave” every year, even when there isnt one (like last year). These warm water events used to be called “Sea Surface Temperature Amonalies” (both hot and cold), and they should be again. Emotive language titles undermines the perception of stability and investability in wild caught fisheries.
I assisted the World Ocean Circualtion experiment fer several years as a ship’s officer, dropping XBT thermal probes, so I know what descriptors were used back then.
Warm water events were reported as occurring around the Tasmanian Coastline since my father was anbalone diver in 1966. He experienced them as an abalone diver, as have I also as an abalone diver. Yet in the past few years, the “scientific” community is makig a big deal of natural occurences.
Lets drop the emotive titles and stick to the facts (for once) in relation to to variation in the rate of change of climate (and water temperature).
ANSWER 1
Written response:
This is an interesting question about language and framing, and how it can be perceived by different groups: scientists want precision, industry may want stability, and the public often reacts strongly to terminology.
You’ve raised several points, which I have addressed below:
The term “marine heatwave” isn’t a rebranding of natural variation. The definition and naming was developed by researchers who needed a consistent, statistical definition for extreme warm-water events (and the converse, cold spells). A now-widely used definition for a marine heatwave is a period when sea surface temperatures exceed the 90th percentile for that location and season for or at least 5 consecutive days (see also – MHW Overview). This is different from “sea surface temperature anomaly,” which is any temperature that is not the average, and can be warm or cold, large or small, short or long. The term “marine heatwave” was introduced because it identifies extreme events, not routine variability, it allows global comparison using a single threshold.
Studies around the world have shown that the frequency (how often) of marine heatwaves is increasing, as is the duration (how long) and intensity (how warm).
Marine heatwaves don’t occur every year in particular locations (e.g. off Melbourne), but in the oceans surrounding Australia a marine heatwave will occur somewhere almost every year. Check out this site to see the current distribution of events – Tracker
Fisheries are not stable, but vary over time. As an example, abalone harvests increase and decrease with the level of fishing effort by commercial and recreational fishers. Other fisheries have changing catches due to environmental events and long-term change.
The oceans are predicted to continue warming as a result of greenhouse gas emissions, and so the frequency, duration and intensity of marine heatwaves will increase, to the point that some parts of the ocean may be in a permanent marine heatwave state. This may occur as early as 2040.
You can see forecasts for marine heatwaves for Australia up to four months in the future at this BOM website. You will see that not all areas of Australia are experiencing marine heatwaves this summer – Ocean temperature long-range forecasts
With shared information about the likely future, both businesses and investors in fisheries can make informed choices.
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