climate change effecting waves

prothero's picture
prothero started the topic in Friday, 22 Apr 2016 at 11:44pm

climate change maybe a decisive couple of words, however its effect on us is noticeable. Previous topics have alluded to the shit waves that Perth now has, Someone said at one stage that sand moves from the Busselton area as far as Perth dumps sand which forms banks, and building of groynes and marinas has impeded the movement of sand. However as we do not have many strong lows from the south to give the coast a good shake up any more , climate change and not groynes and marinas must be the reason Perth no longer has waves........

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thermalben Saturday, 23 Apr 2016 at 7:19am

I don't think climate change can be blamed for Perth's lack of waves. There are very obvious geological reasons why, which we covered in the Coastal Creationism series.

https://www.swellnet.com/news/coastal-creationism/2015/11/16/coastal-cre...

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prothero Saturday, 23 Apr 2016 at 11:29am

Perth is known for its poor waves....Bens link puts that down to geology, Rotto, garden island, and the offshore reefs all do a good job in shutting out the swells. I remember previous years lying in bed and when the big storms came through and hoping that the roof was not going to be blown off. We used to get a number of strong lows from the south that were really intense. I used to look for them in the papers sypnotic charts and plan my surfs accordingly. These lows seem to get less and less which means less sand is getting moved up the coast and getting squeezed through the limestone structures to give the Perth beaches some semblance of a bank........less big lows coming up from the south must be part of climate change .

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tonybarber Saturday, 23 Apr 2016 at 11:47am

I am sure this has been discussed in other forums as it relates to Indian Ocean Dipole. Best is to search through these. Given the El Niño in the pacific recently, there also relevant information the Indian Ocean.
This may help explain the weather perceptions.

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southey Saturday, 23 Apr 2016 at 11:49am

I my limited observation , I'd be waiting for the big pre frontal NW'sters in the middle of the Indian as better sources of swell for Perth . The more west the swell direction the less these geological issues have .
So yeah climate change and limitation of northward frontal projection could be the cause , but for somewhere like Perth I'd be looking for those systems further out to sea . Tends to be less wind associated either too , as the front has reached maximum north trajectory and slides back south of WA on its eastward movement . !?

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southey Saturday, 23 Apr 2016 at 11:54am

Tony IOD is more tropics related .
There is a mid level oscillating which the name escapes me , but the ACW's ( Antarctic Circumpolar Wave ) position. And the SAM (Southern Annular Mode ) or AAO ( Antarctic Oscilation ) are good places to start as likely causes .

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tonybarber Saturday, 23 Apr 2016 at 12:30pm

Southey, thanks for the info. I wasn't sure of the other temperature related phenomenon. I believe there is a significant low forming down the bottom of South Africa. Getting the Jbay guys excited and also for the west of Africa. Maybe too far for Perth.

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Sheepdog Saturday, 23 Apr 2016 at 3:58pm

Off topic, but all across the news is "93% of GBR affected by coral bleaching"..........
This is absolutely misleading and unscientific... Here's an example of one headline;
http://www.abc.net.au/news/2016-04-20/great-barrier-reef-bleaching/7340342

There is no doubt about bleaching... But if the scientific community are going to be anal about how people word things, then their media release should be "ESTIMATED 93% bleaching".... You see, the vast majority of the survey was done visually by plane and helicopter.... There are also over 3000 individual reefs.... the survey looked at 911..... Yet they use the word "comprehensive"...
COMPREHENSIVE; "including or dealing with all or nearly all elements or aspects of something."

A survey of less than 1/3 of the reef is not comprehensive..

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blindboy Saturday, 23 Apr 2016 at 4:52pm

Sheepdog wrote: Off topic, but all across the news is "93% of GBR affected by coral bleaching"..........
This is absolutely misleading and unscientific... Here's an example of one headline;
http://www.abc.net.au/news/2016-04-20/great-barrier-reef-bleaching/7340342

There is no doubt about bleaching... But if the scientific community are going to be anal about how people word things, then their media release should be "ESTIMATED 93% bleaching".... You see, the vast majority of the survey was done visually by plane and helicopter.... There are also over 3000 individual reefs.... the survey looked at 911..... Yet they use the word "comprehensive"...
COMPREHENSIVE; "including or dealing with all or nearly all elements or aspects of something."

A survey of less than 1/3 of the reef is not comprehensive..

Thanks for clearing that up sheepy. For a minute I thought the reef might actually have been damaged. Nice to know it's just an ABC lefty distortion.

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spidermonkey Saturday, 23 Apr 2016 at 4:52pm

Well they obviously have to extrapolate, and it's not unreasonable to do so over similar depth reefs under similar weather patterns.Although I agree the media and department spokespeople are going hard at it. And it's already working, with extra funding announced only recently. I am at sea as i write this involved in a bleaching survey of the reefs of Cairns/Townsville. South of Cairns, not to bad ,North, Mate, it's genuinely fucked!!!! The bleaching could justifiably be considered comprehensive. South of here, not so much. But I agree, a distinction should be made as to which areas have been hit hard, and those further South. Trade winds have well and truly kicked in now,should put paid to any lingering warm water......

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happyasS Saturday, 23 Apr 2016 at 5:26pm

while we're nitpicking over words; who used "comprehensive" ? I didn't see it in that particular article.

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Sheepdog Saturday, 23 Apr 2016 at 7:44pm

BB, it is distorted...

Fine Happy... Here;
"Almost 93% of reefs on the Great Barrier Reef have been hit by coral bleaching, according to a COMPREHENSIVE survey revealing the full extent of the devastation caused by abnormally warm ocean temperatures sweeping the globe."
http://www.theguardian.com/environment/2016/apr/19/great-barrier-reef-93...

And here; "Comprehensive aerial and underwater surveys of Australia's Great Barrier Reef have revealed that the ecosystem is experiencing its worst coral bleaching on record"
http://www.theworldweekly.com/reader/view/newswire/2016-04-20/93-of-grea...

And there's more..... But I'm sure you get the drift.....
Fact - there was a major bleaching event in 1983..... But no go pros, no planes, helicopters with laptops... Back then you had to send your film in for developing.... None of this "press upload"..... None the less, there are records of this major bleaching event, if you want to find it........... Here's one example... If you WANT to find more, you will;
"Coral reefs in the tropical eastern Pacific region experienced catastrophic coral mortality during the severe 1982/1983 El Nino event. "
http://www.int-res.com/articles/meps/26/m026p295.pdf

Then there was another extreme bleaching event in 1997/8;
"The 1997/98 mass bleaching event was extraordinarily widespread. It affected reefs in over 50 countries throughout the Pacific and Indian Oceans, the Red Sea and the Caribbean, and even affected corals in high latitudes including those of the Arabian Gulf."
http://coral.aims.gov.au/info/bleaching-mass.jsp

So, Happy, I'd assume coral bleaching has happened in unison with El Nino since time began.... It's just eg in the 1800s, we didn't have a grasp on it.....
Now, if El Nino's become stronger, and stronger, and less time between each el nino, we may have an issue..... But if we continue to have 19 to 20 year gaps between el nino's, the reefs will recover, like they always have.

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blindboy Saturday, 23 Apr 2016 at 8:12pm

I think if you do a bit more research you will find that it all depends on your definition of " recovery " . If sensitive species are replaced with more resilient ones, which is what tends to happen, then the coral cover may have returned but the community will be changed and will have lost biodiversity. My understanding in terms of the GBR is that your timescale of bleaching events contains only recent events and that there is no evidence of significant bleaching events before mid 20th century. So your claim that reefs will recover. ".like they always have." is totally unsupported by existing evidence.

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southey Sunday, 24 Apr 2016 at 1:06am

Is this a euphemism for people getting kicked off the forum , but only calming back as better human beings - contributors . You know more resilient and all . Evolution Maybe !!!! ?

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tonybarber Sunday, 24 Apr 2016 at 8:23am

Gents, it was not long ago that little was know about water temperature changes in the Indian Ocean which is probably more related to the issue at hand. But I could not help relate the story when we went to the Maldives many years ago and surf what Tony Hindes found. Hindsey told us about the coral reefs dying a few years back (around Sultans). But he said they were coming back. Certainly, there was a lot of fish - various types and ample sea life. But we could see small pockets of recovering coral.

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prothero Sunday, 24 Apr 2016 at 9:02am

.....and then you have coral reefs in North Bali that they have regrown ( through electrical currents)....listening to the media we could easily think we are doomed. David Suzuki (climate scientist) said Humans are creating an ecological holocaust , however he still remains optimistic.

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spidermonkey Sunday, 24 Apr 2016 at 10:14am

"Is this a euphemism for people getting kicked off the forum , but only calming back as better human beings - contributors . You know more resilient and all . Evolution Maybe !!!! ? "

Not really...Corals don,t have the benifit of hindsight

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spidermonkey Sunday, 24 Apr 2016 at 11:38am

The historical record is found within coral cores. Cores taken from porieties corals from the GBR have been dated back to the 1500's. depressingly their seems to be no evidence of bleaching prior to the 20th century. The markers for bleaching events within the cores are quite clear and conclusive....

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prothero Sunday, 24 Apr 2016 at 11:14pm

spidermonkey wrote: The historical record is found within coral cores. Cores taken from porieties corals from the GBR have been dated back to the 1500's. depressingly their seems to be no evidence of bleaching prior to the 20th century. The markers for bleaching events within the cores are quite clear and conclusive....

just looking at an David Attenborough program , changes have been going on at The barrier reef for a long time ,,,,,,,but being the the selfish bastard that I am, i'd like to bring the topic back closer to home , my home.,,,,,South West WA....climate change has meant less storms to form sand banks with which to utilise the swells around Perth.........but more importantly less cold fronts mean less water in the rain water tanks........

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tonybarber Monday, 25 Apr 2016 at 9:40am

Prothero, have a look at Southey post above. The changes you may be experiencing is most likely due to the temperature dipoles in Indian Ocean. Whether these are affected by climate change has yet to be proven.
You would have read about the El Niño in the pacific and its contribution to Hawaii's recent season. Maybe something is happening over in the Indian Ocean. Maybe there were fewer cyclones up in WA.

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Sheepdog Monday, 25 Apr 2016 at 11:34am

spidermonkey wrote: The historical record is found within coral cores. Cores taken from porieties corals from the GBR have been dated back to the 1500's. depressingly their seems to be no evidence of bleaching prior to the 20th century. The markers for bleaching events within the cores are quite clear and conclusive....

Do you have a link to that claim, spider? Because coral bleaching was recognized in the 1800s... And pre then , there weren't too many scientists boating around the reefs of the world..

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spidermonkey Monday, 25 Apr 2016 at 1:19pm

Hi S/D No link, but as I say the records are in the coral cores, taken recently.My"claim" comes from the head Scientist on this trip, who collected and analyzed the cores, I was discussing this with Him last night. He also discovered the markers for bleaching events within the cores, so is able to say with some certainty when historically the bleaching events have occured (I should say major bleaching events). Not sure if He's published anything yet. I am not prepared to name the Scientist or the organization as that could breach my position.Suffice to say I work on an government funded reasearch Vessel,based on the E Coast. The Scientist in question is highly regarded in any case, so there You have it....

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Sheepdog Monday, 25 Apr 2016 at 6:08pm

Spider, To respect prothero, I'll take this over to the climate change thread, and leave this to "affecting waves"....

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prothero Monday, 25 Apr 2016 at 8:37pm

tonybarber wrote: Prothero, have a look at Southey post above. The changes you may be experiencing is most likely due to the temperature dipoles in Indian Ocean. Whether these are affected by climate change has yet to be proven.
You would have read about the El Niño in the pacific and its contribution to Hawaii's recent season. Maybe something is happening over in the Indian Ocean. Maybe there were fewer cyclones up in WA.

TB i dont believe that the dipoles in the Indian Ocean are the driving force in our weather system in SW WA,,or never used to be,,,I feel the Sub Tropical Ridge is /was more important....The STR is a high pressure system that goes around the globe at middle latitudes, in winter this weakens and allows low pressure systems to come up from the south . For 30 years ive been looking out for these low pressure systems and I dont believe they are as frequent as they once were.

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southey Monday, 25 Apr 2016 at 9:02pm

The ridge is stronger , and doesn't allow the the cold fronts to advance as far north .
But as the ridge migrates a little South ( or more so expands ) over a long time period ( decades ) .
Then this itself will condense the westerlies to its South . The SAM is the index which measures where the strength of both the LWT to the south and STR to the norths confluence meets . Ie how far nth Fronts are allowed to extend . Often it is longitude like length ( width ) of such ridges that denies the fronts northward advancement . But the other thing is dominance or prevlence of the ridge to re instate itself after a gap is forced by either. Low from the south or north .
So you end up with smaller longer period swells , which will feel that shallow bathymetry a lot more than storm swell with less wavelength . Long periods can massage banks into perfection , but often don't shake things up unless they are overtly large . Smaller , shorter sharper frontal blasts move that near shore sand .