Cool Streaks In South Oz
Cool Streaks In South Oz
It was around this time last year stunning satellite imagery from the South Australian coast came in, depicting a beautiful, fluorescent phytoplankton bloom emanating off the Bonney Coast. That being the region immediately north-west of Tasmania, from Portland through to Robe in South Australia's South East.
It's a yearly event during summer under strong, persistent south-southeast blasts and this year we've got another great satellite signature of the upwelling, spreading with the associated currents to the west, towards Kangaroo Island.
There's no trickery being played with the visuals, this is the true colour imagery seen from space and what it depicts is one of the most significant upwelling systems in the world and the largest predictable one in south-eastern Australia.
(NASA Terra/MODIS)
Like the East Coast under strong north-east winds, strong south-east winds along the western Victorian and South Australian coast direct surface water to the left (opposite in the Northern Hemisphere), known as Ekman transport.
This transport of surface water to the west, away from the coast results in a drop of the sea level locally on the coast, which with all things being equal needs to be balanced. This is done by drawing up water from the depths, which is cooler and nutrient rich.
The unique characteristic regarding the Bonney Coast is the close proximity of the shelf break to the coast, only some 30km or so at its closest point.
This and the various canyons lining the shelf provide the perfect setup to pump cold, sub-surface water up from beyond the shelf.
Once the cool, nutrient rich water reaches the photic zone, where sunlight enters the water column, photosynthesis takes place, the fundamental building blocks for production in the ocean.
Current observations have water temperatures between 3-4°C below normal off the South Australian Coast, spreading westward though with less strength into the Bight.
This and a similar upwelling signal off the Pilbara Coast are the only areas that aren't warmer than normal Australia wide.
The upwelling zone is a key ecological feature and an area of high primary production and aggregation of marine life, tiny to large.
During summer, persistent south-southeast winds are prevalent across the Victorian and South Australian coasts, but the past month we've seen these winds coming in much stronger than normal (as most surfers can attest to).
With wind speeds being 3.5m/s (6kt) stronger than normal, we've seen a significant upwelling event with the resultant phytoplankton bloom being visually striking.
Wind anomaly (difference from normal) for December and Sea Surface Temperature anomaly January 9th (inset) (NOAA)
The associated surface currents are also pushing the bloom to the west with localised eddies clearly visible.
The bioluminescent properties depend on whether the bloom contains dinoflagellates which appear brown in colour, with possible signs showing in the western arm of the bloom.
Comments
Wow. Fascinating. Almost looks like a big wave heading for the Coorong.
As mentioned in previous threads, the potential for a correlation between the number of sharks on the Eyre/Yorkes and this upwelling is something to take into consideration.
Btw those same howling SE winds have been a nightmare on the S coast of WA too. Worse than the last 3 years which were horrendous. Blowing in alot of cloud and some moisture off the Bight. About as miserable as it can get.
Seems the water is a lot cooler too although the charts are saying it's as normal. Would have been happy in a 4/3 this morning!
How's the air temperature anomaly from December for the Bight from all the onshore winds, cloud and upwelled water..
Wowee!
That explains the cool land temps we've been getting as opposed to Perth. Sometimes as much as 15degrees difference!
‘Btw those same howling SE winds have been a nightmare on the S coast of WA too. Worse than the last 3 years which were horrendous. Blowing in alot of cloud and some moisture off the Bight. About as miserable as it can get.
Seems the water is a lot cooler too although the charts are saying it's as normal. Would have been happy in a 4/3 this morning!’
Second that, I recently noticed a few little brain freeze headaches at the start of ocean swims. Unusual for this time of year
It's unreal to finally understand the regional processes that contribute to all of these phenomena. Way back in the day, we never understood (and truth be told, never questioned) why this neck of the woods was so cold through the summer months. It was just accepted as such.
many years ago surfed yorkes for a few days in april then went to tassie was shocked how warmer the water was to sa, this chart explains why.
Having lived in both states, I'd say the East Coast of Tassie is much warmer than SA in the summer. I regularly surfed in boardies and a vest in Tassie, something that doesn't often happen in South Oz.
The winter, however, was a very different story.
Yeah, love this sort of content on Swellnet Craig. Makes the subscription price even more than worthwhile. Is this the sort of plankton that attracts blue whales that are known to frequent this region? We live in an amazing world, I hope we don't stuff it up.
Thanks Weatherman, and indeed it is!
https://bluewhalestudy.org/the-bonney-upwelling/
Sheepy any possibility of you taking an Inshore Water Temp ?
This might explain why summer is southern bluefin tuna time in SA and also for Portland, which is a bit of an anomaly in rec fishing circles as being home to larger than average fish. Pilchards probably feed on the phytoplankton, and tuna love a pilchard.
Nov last was definitely the strongst SE'lies I've ever experienced...from Cactus to Portland it blew incessantly... I reckon we had 1 day of northerly...maybe 2.
Another compelling article Craig, and as with Weatherman love this content.
Still think there’s something to the relationship of upwellings and shark attacks / numbers. Sic another one this week on the west coast. Be interested if anyone has any info
Definitely worth some research, Bronco (and Craig). The timing seems to be about right. If I was studying marine biology it'd be my PhD and likely a well read one.
Was going to ask about the correlation between this upwelling and bluefin tuna runs.
Thanks Chin.
Can't really add anything to the above except that I really enjoy these articles too and that's why I keep coming back.
Reminds me of the northern lights.
@craig , currently in sanur the water is like a warm bath , in close to shore that is . On Lembongan it’s actually really cool and a shock at first when you jump of the boat . The channel between Bali and Lembongan is only 800 meters deep at the deepest point and varies down to 200 meters. The distance from sanur to Lembongan is 17 klms and to padang bai about 12 . What causes such a huge difference in water temperature ?
Vertical Currents
Google vertical currents Lombok Strait Research Gate - For some reason i cant Link it
Some great Info on that Strait.
Yeah thanks udo , I did actually google what you put up the other day when we were talking down currents . It’s just amazing such a difference in temperatures, come August it’s actually fucking cold water and the locals are shivering.
Awesome article Craig.
Much appreciated!
Thanks guys, this stuff is so interesting.
Also had a comment on my insta from a boaty who went through it Tuesday..
"Drove through this yesterday out in the boat before I heard what it was, water was the same colour as it looks in those sat images, amazingly aqua blue with distinct lines around the edges. Should have taken some photos in hindsight as I’d never seen anything like it."
Yeah that was I. Also of note the annual Southern Bluefin Run off the back of Victor/KI has been extremely slow this season. There are a few fish out there but no where near the numbers for the last decade you would expect to see at this time. Tuna usually start rocking up in December and are everywhere out there, not the case so far this year. Interesting month ahead to see if they show.
Last year it was all the fresh water from the floods extending across to the back of KI showing on the imagery. Many though this caused the tuna to change migration as there were tonnes of them all up the gulf and being caught of Adelaide metro.
Very interesting, you think they might be on the southward flank of the cool water plume? In the warmer water..
Pretty profound comment and observation that just adds to the list of things stacking up.
thanks heaps!
There really seems to be an anomally in climatic events this year from all anectodotal evidence?
It's crystal clear on the ground here. I can't even explain the magnitude of how bad this summer has been for extreme howling SE winds, immense cloud coverage and super cold waters. Never seen anything like it. Honestly feels like the end of days...and i'm a positive person!
btw,,,An observation from afar... it's been a shit Hawaiian season as far as El Nino goes to this point. Howling onshores with the odd big N swell thrown in the mix. Not the classic El Nino Hawaiian winter so far..
Nature is also going off down here in Tassie at the moment.
We've experienced an extended period of major auroras, we have a marine heatwave pushing surface temperatures into the low 20's, our beaches are being invaded by flotillas of blue bottles, along with bioluminescence displays throughout our coastal waters and estuaries.
Nature is talking to us and we need to listen more.
Amazing! Haven't seen a blue bottle in years here on the Sunny Coast. Great article Craig.
fascinating - thanks
Any correlations to the shark attack numbers? Or is SA just f’ed
GW Sharks attack in different temperatures
Wa and Nsw not cold,
There was 23 seen at Neptune Islands yesterday!
And yet another day of howling howling ESE winds here.
Just looked and the water temp is down to 16degrees! 16!!!
Been speaking to a few people who have beach houses at Kingston SE & they have all commented about the colour of the water even in close this summer and how cold the water is.The water temp out wide seems to have shut down the whiting fishing also
i
Warning to all East coast hipsters, don't come to S.A. Every spot is jam packed with hungry sharks. Stay home, leave the mid-length twins and logs on the troopy in the shed and spin some vinyl.
Worst summer for surf on the mid and south coasts in living memory. Howling S.E. winds and bugger all swell for two months. Hopefully it will come good when the school holidays end. The water temp is ok here though, it's been nice in boardies and rash vest on the few small hot days we have had. Cheers.
Last few weeks have been the coldest summer of surf, weather , i have had, since the 70s in far west Vic , think ice cream headaches , ball biting cold wipeouts, freezing hands and feet, even with top of the range wetty and hood, a long session now is just a grind , one of the pro fisherman said it got so cold it killed the pippies on the beach wtf, out of curiosity today i took a thermometer with me and put it in the water in the shallow lagoon , it was soon at 10 celsius in water that felt a lot warmer than out the back of the reefs i had just paddled in from , been in a 3,2 wetty twice since winter , hardly seen the sun in the constant overcast cloud , weird sea mists and howling easterlies, bring on winter at least the water will be warmer .
I have a good mate who is a commercial fisho and fishes for pippies in South West VIC. Not that long ago there were so many pippies on the beach you couldn't see the sand now nothing. Just told me this morning he's had reports of dead crays , abs, and fish washing up on the shore around Port macdonnell .
yeh, the die-offs seem to be shallow/reef fish, used to warmish water, lotsa wobbegongs, etc, but so far they are blaming fresh-water run off from 8 mile creek, which makes no sense (small creek, mostly aquifer-fed, nothing in the way of tributaries, flat land).. no big fish die-offs at Glenelg River outlet, or along Discovery Bay, where the pippies are depleting.
Scientists in Sth West Vic/ Sth East SA, must be really intrigued.
(Portland has had an Upwelling Festival for 15 years or so. Best reason for a festival ever).
Yeah surely the abrupt drop in temperature and also increase in salinity from the upwelled water would have been the main cause?
Is the cold upwelling water suoer-salty craig? I didn't know that.
Really interesting point you make, they are testing for toxins, salinity, disease, but you can't test for temp drop in a lab.
(die-offs might be part of a much bigger picture, the upwelling, so many species depend on the nutrients, phyto/zoo plankton right up to the top of the chain.. ironic if it wipes out a bunch of stuff too.. but with so many detritus feeders, crabs/crays/cockles, etc. maybe it all just adds to the melange of life. Not good about the pippies tho)
It's nutrient rich, and saltier afaik
Yep, salt water is denser so sinks to the bottom and cools. So when upwelled it's salty, cool and nutrient rich.
decided to drive across to port macdonnell today with a mate and my kids, we drove along the beach from 8-mile creek to picaninnie-ponds outlet, kids kept a rough count, and stopped at ABOUT 250 wobbegongs (4-5 foot), 100 PJ sharks (many as small as 1-2 foot) - many crays all sizes, some monsters, some smalls.. dozens of other fish..
Local fishos blame sudden cold water for pippies/cockles die-off. In the Discovery Bay vicinity, if they are there, they are dead and black inside,
and they blame red algae blooms for de-oxygenating the water for in-close fish.. we didn't see a single school or 7 gill shark, saw snapper dead, but no mulloway or salmon...
Cold upwelling during summer is well known about.
"Bonney coast upwelling" is a celebrated annual event right?
Yep.
Meanwhile water temps in Sydney and south coast nsw are hitting 24c and plenty of light se winds., more humidity. Absent is the howling ne winds and upwelling. It’s all linked
A bit late to the party here, but having read the article and many of the comments I wonder if the (much smarter than me) folks at Swellnet could do an article tying all of this together? The unusual summer temperatures, increased rain, winds, positive SAM, upwellings, the (unusual?) activity in SA's S swell window, fish migration patterns and shark attacks.
Not saying they're all linked - they likely aren't - but it could be useful from a surf perspective to have one article which ties it all together and gives us the pieces to understand why the El Niño that was promised has severely underdelivered for us on the surf front.
Kind of like the ABC did here: https://www.abc.net.au/news/2024-01-21/whats-been-driving-australia-clim... but with the surf focus you guys consistently nail.
Hopefully more to come with that
anybody remember the name of the app that previous contributor mentioned for ocean sat images, that was brillian, but have since lost it
abc news
https://www.abc.net.au/news/2024-02-02/ocean-upwelling-brings-deep-sea-v...
There ya go!
Great article. Cheers Rob.
Thanks that's a bit of good news,
Orcas welcome
https://www.abc.net.au/news/2024-02-02/ocean-upwelling-brings-deep-sea-v...
Thanks mono, great little explanation there
Great Southern Reef Website
Continues from above : 11th Jan ~ Craig's link to Blue Whale Study
https://greatsouthernreef.com/upwelling
Incredible TBB!
More amazing interactions from the Bonney Coast Upwelling System..
https://www.abc.net.au/news/2024-04-03/blue-whales-racing-in-southern-oc...
cheers craig, interesting. not a fan of the seedy anthropomorphising of other species' sexual behaviour, haha, but lead to some good reading, I didn't know the upwelling had been a bit sucky this year.. adds still more weight to being incredulous about proposed Port Macdonnel (and other) offshore windmills..
Actually it's been too active, that's what they're saying. They need the winds to settle and waters to warm back up..
ah, cheers, you accurately refer to just the cold/nutrienty/salty water-surge as the upwelling, laymen like me use the term upwelling to cover the phenomenon and also its knock-on effects. schooled! ; )
While surfing today the water was warmer and clear , possibly signalling the end of the great 12° chill of 2024
"the great 12° chill of 2024" haha, great reel title.
Nice!