Melting Sea Ice Brings Rare Groundswell
It’s not often that the East Coast experiences groundswell periods in the high teens, let alone over twenty seconds, but one such swell is currently filling in across New South Wales.
While being open to swells from a wide variety of directions, the east facing nature of the aptly named East Coast is shadowed (Tasmania I’m looking at you) and angled away from the brunt of most Southern Ocean storms.
Savvy chart watchers and Swellnet readers would have been alerted to the fact that a flukey but strong south-southeast groundswell was due to build across southern NSW through today, with its source being a rare occurrence.
That being hurricane force winds inside the Ross Sea, below the Antarctic Circle at a latitude of 70° south. Swell generation in this region is rare as it's usually covered by sea ice, even through summer, but the last four years have been the lowest recorded Antarctic sea ice coverage on record - 2023 being the lowest on record.
The current sea ice extent chart as of March 23rd below shows a chunk of ice missing inside the Ross Sea - see chart below right. It also compares the current sea ice extent to the median extent from 1981-2010.
On Friday evening, we saw a significant polar low pushing east, far below New Zealand. On the southern flank of the low, a rare fetch of hurricane-force S/SE winds were produced in the Ross Sea, squeezing against the Trans Antarctic Mountain range directly to the west, setting in motion a strong, long-period south-southeast groundswell.
Sources: Weatherzone and NASA
This source is so rare that it's outside the range of our forecast WAMs and also outside of the scope of satellite scatterometer (wind) and altimetry (sea height) observations. Fortunately it was picked up by our forecaster team and shows in the forecast model output as a small but distinct, 20+ second groundswell.
Buoy observations picked up the leading edge yesterday afternoon off the southern New South Wales coast with periods sitting well over 20s, and since, the buoys further north have all picked up this strong groundswell and recorded peak periods between 19-21s.
Even the Tweed Buoy spectra is registering a faint signal of 22-23s swell.
Swell periods are correlated to the core wind speed within a swell-generating fetch, with the stronger the winds, the larger the eventual swell period as it travels away from the source.
With the source winds reaching an incredible 70-80kt, swell periods in excess of twenty seconds were always going to be the result, though the small and tight nature of these winds along with the large travel distance (over 4,000km) have only resulted in 4ft waves across the southern NSW coastline. The long-period nature is also resulting in super straight, beach-long closeouts that are more suited to reef breaks.
Macquarie Island situated due south of New Zealand would have seen the bulk of the energy with waves wrapping around both sides of the island. Similarly, Lord Howe Island in the middle of the Tasman Sea would have long period swell filling in on both sides.
As sea ice extent continues to shrink with a warming climate, we could possibly expect the frequency of these swells to slowly increase, though it’ll take a sharp eye to identify them from such a flukey source.
Comments
Far out.. that's pretty amazing
Will this work for Hobarts fickle points?
Nah too small.
Presumably it benefits spots down around Southport, patches of Bruny and perhaps even tucked up towards Swansea?
Thought it was 1st April for a moment :)
crazytown! thanks craigo
Interesting article & confirms what I was watching this morning. Thought it was flat, then a strong pulse of swell out of nowhere, too straight for the banks though.
If I was still in Sydney I could have ventured down to Era point and possibly scored.
Not too much here early but has definitely picked through the morning...super straight and long waits...not much at all between sets and then some solid 4fter's to clean up the pack.
Great article again Craig!!
Great article Craig, very interesting. At 6.15am a cursory glance revealed nothing but 5 minutes of peering through the gloom showed it was definitely worth suiting up. Some fun ones before the wind and tide got into it.
My old local thrives on these Ross Sea swells, so I've been watching them for about 20 years. They're not that rare, thankfully.
Very nice.
Second that IB . I look out for pulses waaay south and hit a couple of south magnets that nobody knows of .
Just drove the coast around here and without any background swell we've got abject flatness punctuated every ten minutes by a set. A great novelty swell to watch but you wouldn't call it user friendly.
you see anything much of interest? i'm about to head out the local for a punt. for obscurity, it's a spot you'd hope was inaptly named.
*this message self-destructed*
That swell hit the Lower North Island NZ yesterday afternoon. Pumping today at various spots. We get something like between one and three of these a year. There is a very short window for them. Island Bay tuned me into them about ten years ago.
How good! Yeah they are rarely well aligned for the Australian East Coast so less common.
It's also an extra thousand kilometres of travel compared to Wellington (fifteen hundred more than Dunedin too) - and thus the additional swell decay.
It was 6-8ft where I surfed today. Very powerful. It's a spot that comes out of deep water and it really focusses the swell. Other spots nearby were 2ft. It was just one of those swells. I hadn't considered that a Ross Sea swell would make it to Australia, but it makes sense now I think about it.
Yep, true.
As Spuddups said, the peak season is short, and some years the Ross Sea never becomes truly ice free (one of my small daily jobs is to plot the ice edge in the S Pac). But even a 2/3 ice free Ross Sea opens up that window to longer period swells.
So good to see how one of Spuddups' favourites lit up today.
'Kin oath. It was one of those days you dine out on for months. It'll go into my surf diary as a 9/10.
Ha, got it!
Here's the Tweed signature picking up energy between 19-24s..
Fark, I love geeking out on swells and fickle spots etc.
Today's interesting NZ surf fact was that the west coast got an 18sec swell too. Rare double whammy.
And how pumping was today? Models under called? I saw shots of Lyall Bay cooking and wondered where that swell had come from. Fascinating. Hope you got your share
So good. Better than last Thursday/Friday, I reckon, and a lot less crowded. You get some?
Got one from outer boil Outsides to Keyhole (~900m according to google maps). My longest wave ever, easily.
That area with the big rock in the wairarapa?
Nah, North Island west coast. Not a secret spot.
Ahh gotcha, different swell source then.
Yep, and very rare to have ~18sec swells on both coasts.
Agreed, imagine if there had been one of those super rare North Pacific N ground swells hitting Northland/Coro at the same time!
Oh that's awesome. Next you've got to make it through Whale as well. That's probably 1.2 km. I've done it twice but it was years ago and had to be really wide across the valley. I've had lots myself lately too and sounds like another swell tomorrow. An awesome time of year ay
Yep, that's a long way. Good work.
I had a few during the big swells last summer from Indies to the Pinnacles. Seemed to take 5 seconds, haha!
Wow thats interesting.
Shame the wind was into, few bombies reefs starting to break
The new norm?
Arctic polar ice cap & Antartica melting.
Northern Polar bears & Southern penguins starving.
Extreme bushfires and floods across the planet.
4wds thriving.
"Reports from Bribie Island say that up to 1,200 4WDs hit the beach per day"
"The market has shifted with 4WDs now 46% of new cars (as of 2024), expected to top 50%..."
https://www.swellnet.com/news/swellnet-dispatch/2025/03/24/push-4wd-beac...
Enjoyed this swell with Spuddups today. Got excited when I saw it on the models. It takes about 3 days to get up here. You're right that the beachies don't like that much period, unless there's a great tapered bar. They tend to unfold too fast.
They don't tend to show here - but when they do, it's an insane angle for the points here if the bank is good.
No sign of anything here on dark.
Majority of Australian & Timor natural gas has been exported; to help O/S nations meet their required CO2 reduction targets & energy needs, since John Howard as Prime Minister signed a 30 year contract in 2002.
We received a gift of two giant pandas to Adelaide's zoo..... on loan
https://www.smh.com.au/opinion/how-australia-blew-its-future-gas-supplie...
3-5ft at a south swell location north of Newy on the mid north coast, straight lines n long lefts.......followed by 20-30mnutes of flatness!!
Well spotted Craig, great analysis. Sounds like a good explanation for a bit of 'surf magic' that happened when we were grommets. On a flat summer's day, early 1970s, at a reef break in West Oz, with nobody around, we burned a board as a sacrifice to Hughey, while jokingly chanting and praying for the conditions to change. Not long after, we watched in awe, as a set of waves from seemingly nowhere suddenly appeared and peeled off perfectly in front of our incredulous eyes. The very long interval, after that magic set, sure made us wonder. Apologies for chemical pollution in burning a board on the beach. We were optimistic, fun-loving, but very ignorant grommets indeed.
I love snooping around down there for crazy winds but never occurred to me it was supposed to be covered in ice. Thanks for the education!
I didn't get the chance to see the ocean this arvo, but hoping to find a few presents from antarctica in the water tomorrow.
The charts are horny for another fetch this weekend.
Yeah you spotted it last week!
Love this Craig thanks
Swell from a distant source
Hits south of the north with force
Antarctic swell watchers ditty
Ps -The southern Ocean maps are the most 'normal' looking Autumn I've noticed since Nina/Tonga Volcano.
Lucky to be at the in-laws in Wellington this week - not super familiar with the zone so just battled the circus at Lyall bay. Was super fun with surprisingly pleasant water temp.
Did anyone surf the points? I thought it would've been too small and went for a wedging back beach instead and got totally skunked. It was neither wedging or even breaking ok. This autumn sucks.
love your work Craig … I am fascinated!! It’s registering on today’s data at Byron buoy.
Great stuff Craig.
"Scientists Reveal What Antarctica Would Look Like With No Ice."
https://www.sciencealert.com/scientists-reveal-what-antarctica-would-loo...
Their new map of Antarctica as it lies under the ice is the most detailed yet – revealing mountain ranges, ancient riverbeds, deep basins, and low, sweeping plains.
Probably be a few fun set ups in there somewhere as well. Surfable 24/7 during summer!
Wouldn't be out of place in an Alien movie.
https://www.glowm.com/article/heading/vol-18--ultrasound-in-obstetrics--...
https://en.wikipedia.org/wiki/Umbilical_cord
Same system to provide the warm up session at Punta Roca too!
Great article, I admit I don't spend much time thinking on angles like this. I do know with the great circles systems off Florida can deliver very long range groundswell to SW WA, but tend to file that in the 'curiosities' dept. Are there any weird angles (apart from the obvious SE wind pattern and the far S swells under Tassie bending) that can get into the Surfcoast that would spin us out Craig?
Any reports from Tassie?
I wonder whether Tassie might have been too far around the corner for this one...? Bit more of a direct hit for the NSW coast and certainly for us here in
Sth coast NZ
Yeah it was. It received less size than the NSW region.
Drove the entire east coast yesterday to Hobart and it obviously missed this coast.
Good question Memlasurf!
I was wondering about a certain sand bottom right hand point on Tassies east coast. I really know nothing about it, but have imagined perfection unfolding under the most precise swell direction.
Got a feeling it might have been pretty good!
Here's an image of the Windy waves model I screenshotted when I saw the setup.
find duplicate values online
Fake news
Amazing. So as global warming gets worse and there is less sea ice, these will become more common?
Never thought of that connection
Could be twice in 2 weeks.
The fetch this weekend might add a nice bass line in the background later in the week.
Hopefully good for the back half of El Sal as well.
Indeed!
Yep, EC on Monday
GFS looks a bit better as well. Very interesting.
Thats a good looking map for the Wellington coast ay IB? Does swell ever sneak through Cook strait? Looks like some good set ups around Mana etc. I flew over there today and was spying out the window
Yes, it happens. And yes, it a whopping low - hope it coincides with good winds.
Wow, Ross Sea part 2 delivered in spades. I wasn't there, but Spuddups and Yendor might mumble something cryptic once the shock wears off.
Everyone's scoring. Unreal!
Carn Spuddups and Yendor, start mumbling.
May or may not be apposite, but I was down the south coast of NSW about 10 years or so ago and lucked into a very mysterious swell. There was nothing in the water, then every 10 to 15 minutes a long period 3-4’ pulse would come through in pristine, but cold, conditions.
Direction suggested something from south to south east east of NZ, and reports from others that day indicated that none of it got even as high as the Illawarra. The rest of the coast further north was flat.
I reported it to Craig at the time, a mysto swell which could only have come from something like this.
I had it to myself for about two hours, which equated to about 10 waves. Can’t imagine how many guys came by the car park and said to themselves “what the hell is that guy doing out there, and so far out.”
Will look for the second coming which I think Steve alluded to in his notes for later this week.
Glad to hear others got a few from this. Me and the mates took a tinny down to the north side of Sturge Island where it was offshore and snagged some screamers. Afterwards we headed to Zuccelli station and hooked up with some hot Italian chicks - those Antarctic researchers really know how to party.
Those clips of the corner at Lyall Bay looked amazing. I can only imagine how good it was out Cape Palliser way
Here on the MNC the second Ross Sea swell showed up better than the first, lasted longer too. Noticed its longer period energy wrapped in and ran pretty well, more so than the much closer source, shorter period swell. If only it had another foot or two.. Still, had soo many sick waves this last week and feeling all the better for it. Fuck I love autumn.
Deffio showed better here too but local winds were av and banks were crappy so it was another miss as far as wave quality goes.