Sydney Breaks SST Record

Craig Brokensha picture
Craig Brokensha (Craig)
Swellnet Analysis

It'll be no surprise to Sydney-siders - who've been in boardshorts since last November - that the sea surface temperature record was broken two days in a row at the start of the month.

The Manly Hydraulics Laboratory’s Sydney wave buoy, which is situated approximately 10km off of Long Reef, hit 26.75°C on both Wednesday the 8th and Thursday the 9th of March, breaking the February 2022 record of 26.6°C.

Meanwhile, inside the surf zone it's been hovering between 23-24°C.

Sea Surface Temperature observations off Long Reef, Sydney, since 1993. Note the red trend line and record 26.75°C temperature marked by the red dot. (MHL)

Further out to sea, temperatures were even higher, reaching 27°C as a warm tongue of the East Australian Current protruded south. To the north it's even warmer, sitting at 28°C offshore from Yamba and Byron Bay, resulting in oppressive humidity, only broken today by the first proper incursion of cold air from the south.

Humans regulate our body temperature through sweating and evaporative cooling. The relatively drier air around us helps transfer heat away from the body through the process of evaporating sweat.

But when this air is itself highly saturated, then the process becomes less efficient, even to a point where it doesn't work at all and we start to overheat. This is the issue confronting many with the warming oceans.

Sea Surface Temperature observations off the Southern NSW coast (March 4th). (BOM)

But how does warmer water increase the humidity?

Again, by the simple transfer of energy. The warmer the water, the greater the rate of evaporation, transferring water molecules into the adjacent air mass as water vapour.

This makes the coastal air mass more humid, which in turn creates increased humidity anywhere east of the dividing range, where the humid air becomes effectively trapped.

The below chart shows the precipitable water anomaly for the past three months.

Precipitable water is a good proxy for humidity as it shows the amount of available water in the atmosphere for possible rainfall. The higher the values, the more saturated the atmosphere, while the lower the values, the drier it is.

The anomaly shows the difference from the long-term climatic mean (1991-2020) and what stands out is the increased precipitable water values off the East Coast (on top of already humid weather expected through summer). Also note the dry slot off Western Australia, driven by persistent inland south-easterly winds. This lead to Western Australia experiencing their hottest summer on record.

Precipitable Water anomaly for the past summer. (NOAA)

It's not just the East Coast that's experiencing warmer than normal temperatures, Tasmania has been very mild in the ocean thanks to the extension of the East Australian Current pushing down their East Coast, making it into Storm Bay (2-3°C above average). Bass Strait has also seen temperatures coming in 1-2°C above the long-term average.

This is following an El Niño year, which typically brings cooler sea surface temperatures to Australia, yet this time the trend was bucked with global temperatures coming in at their highest on record during 2023.

There have also been multiple reports of tropical species making their way further south with the currents. A highly venemous yellow-bellied sea snake washed up at Manly earlier this week (see left - photo thanks to Philip Eastburn), with another making it all the way to Pambula last November. Another account was of a green turtle that made its way into Hobart's River Derwent at the end of January.

Looking ahead, and the East Australian current still has a plentiful supply of warm water from the Coral Sea and this should maintain warm sea surface temperatures well into the second half of autumn. It'll just be a matter of donning a wetty top to keep the cooler air temperatures at bay.

Special thanks to Manly Hydraulics Laboratory for the collection and provision of wave and sea surface temperature data on behalf of the NSW Department of Climate Change, Energy, the Environment and Water.

Comments

Iced vovo's picture
Iced vovo's picture
Iced vovo Thursday, 21 Mar 2024 at 4:59pm

Great article, the humidity was all time this past summer, no reprieve at all. Had a sea snake wash up on our local beach in the lower Hunter as well.

velocityjohnno's picture
velocityjohnno's picture
velocityjohnno Thursday, 21 Mar 2024 at 5:43pm

"To the north it's even warmer, sitting at 28°C offshore from Yamba and Byron Bay, resulting in oppressive humidity, only broken today by the first proper incursion of cold air from the south.

Humans regulate our body temperature through sweating and evaporative cooling. The relatively drier air around us helps transfer heat away from the body through the process of evaporating sweat.

But when this air is itself highly saturated, then the process becomes less efficient, even to a point where it doesn't work at all and we start to overheat."

Sounds like a barrel of fun.

freeride76's picture
freeride76's picture
freeride76 Thursday, 21 Mar 2024 at 6:14pm

I had an ice bath set up for about 6 weeks and jumped in it 2 or 3 times a night.

Lanky Dean's picture
Lanky Dean's picture
Lanky Dean Saturday, 23 Mar 2024 at 1:12am

W T F
I thought you were allergic to cold water?

Panman's picture
Panman's picture
Panman Thursday, 21 Mar 2024 at 7:49pm

I surfed at Ulladulla yesterday and the water was bloody cold

flollo's picture
flollo's picture
flollo Thursday, 21 Mar 2024 at 10:11pm

Loving the water temperature at the moment. Good to hear it will stick around till winter.

AndyM's picture
AndyM's picture
AndyM Friday, 22 Mar 2024 at 10:52am

The old-timers around here reckon it was the hottest summer than can ever remember.

Bustard's picture
Bustard's picture
Bustard Saturday, 23 Mar 2024 at 7:00am

The old timers around here reckon it’s the hottest summer they can never remember

simba's picture
simba's picture
simba Friday, 22 Mar 2024 at 12:09pm

hottest and most humid...mate in kalbarri said they have had 5 days this year of 49...........and many over 40

velocityjohnno's picture
velocityjohnno's picture
velocityjohnno Friday, 22 Mar 2024 at 12:39pm

Yeah NW and midwest WA got cooked.

Slackjawedyokel's picture
Slackjawedyokel's picture
Slackjawedyokel Friday, 22 Mar 2024 at 1:49pm

Hottest Indo wet season I can recall. Maybe it’s cause I’m not as match fit over there as I once was but from late October till recently was sweltering.

And that’s why on the sixth day Huey created Bintang and Pocari Sweat.

BTW…if you ever see one of those yellow bellied Sea snakes, give it a wide berth. I found one on the beach around Nth coast NSW a few years ago and tried to put it back in the ocean. It wouldn’t get through the Shorey so I took it up where a creek empties into the ocean and let it go there. I was fully handling it in the belief that they had fangs at the back of their mouths and they couldn’t open their jaws wide enough to bite a human except on webbing between fingers and toes etc.

After letting it go I read about them and apparently they are extremely, extremely, extremely venomous and they can open their mouths almost 180 degrees so can bite you on flat surfaces such as your thigh or arm. They have these tiny mm long teeth thst just have to graze you. Not long later your lungs don’t work and half hour after the bite your heart is stopping .

Stupidest thing I’ve ever done was being cavalier with that little snake.

But it’s not rare or unknown to find them in Sydney or further South.

https://www.australiangeographic.com.au/fact-file/yellow-bellied-sea-snake/

Hati Hati!

Lanky Dean's picture
Lanky Dean's picture
Lanky Dean Saturday, 23 Mar 2024 at 1:25am

I learnt about these as a kid on a road trip to cape trib.
Box jellys, blue rings ,crocs and sharks .
Stay well clear.

drchris's picture
drchris's picture
drchris Sunday, 24 Mar 2024 at 9:26am

those sea snakes been washing up around torquay 2022-23 summers as well. plus blue bottles in the easterlies at all time levels at moments. signs of the changing climate times

Robwilliams's picture
Robwilliams's picture
Robwilliams Monday, 25 Mar 2024 at 8:52am

excellent tbb . filter feeders and more, climate and environment having big impacts across a broad range of global industries and economies.

mowgli's picture
mowgli's picture
mowgli Tuesday, 26 Mar 2024 at 12:43pm

It's just like how the scientists predicted!!!

What I wanna know is, why isn't the government investigating how these scientists and "big climate" have engineered the weather and are making the place warmer and threatening the lives of hard working cobbers visiting the sunny coast for a dip/enormous yacht owners with HIGHLY VENOMOUS and VERY ATTRACTIVE* sea snakes, just like they said would happen. The nerve to tell us all what would happen and then they actually do it and it does! #blameAlbo

* (but not in a weird way / but yeah maybe also in a weird cos they did legalise gay marriage and I think it was Barnaby and the Mad Monk that warned us it would make me sexy into animals and a now that I think about a snake is doodle-y so yeah gay marriage and all checks out. Kinda makes ya wonder what else they've done to us without telling the truth #vaccines #getyerfactsright #wakeupsheeple)