From Oregon State University:
Ancient tides different from today – some dramatically higher
CORVALLIS, Ore. – The ebb and flow of the ocean tides, generally thought to be one of the most predictable forces on Earth, are actually quite variable over long time periods, in ways that have not been adequately accounted for in most evaluations of prehistoric sea level changes.
Due to phenomena such as ice ages, plate tectonics, land uplift, erosion and sedimentation, tides have changed dramatically over thousands of years and may change again in the future, a new study concludes.
Some tides on the East Coast of the United States, for instance, may at times in the past have been enormously higher than they are today – a difference between low and high tide of 10-20 feet, instead of the current 3-6 foot range.
And tides in the Bay of Fundy, which today are among the most extreme in the world and have a range up to 55 feet, didn’t amount to much at all about 5,000 years ago. But around that same time, tides on the southern U.S. Atlantic coast, from North Carolina to Florida, were about 75 percent higher.
The findings were just published in the Journal of Geophysical Research. The work was done with computer simulations at a high resolution, and supported by the National Science Foundation and other agencies.
“Scientists study past sea levels for a range of things, to learn about climate changes, geology, marine biology,” said David Hill, an associate professor in the School of Civil and Construction Engineering at Oregon State University. “In most of this research it was assumed that prehistoric tidal patterns were about the same as they are today. But they weren’t, and we need to do a better job of accounting for this.”
One of the most interesting findings of the study, Hill said, was that around 9,000 years ago, as the Earth was emerging from its most recent ice age, there was a huge amplification in tides of the western Atlantic Ocean. The tidal ranges were up to three times more extreme than those that exist today, and water would have surged up and down on the East Coast.
One of the major variables in ancient tides, of course, was sea level changes that were caused by previous ice ages. When massive amounts of ice piled miles thick in the Northern Hemisphere 15,000 to 20,000 years ago, for instance, sea levels were more than 300 feet lower.
But it’s not that simple, Hill said.
“Part of what we found was that there are certain places on Earth where tidal energy gets dissipated at a disproportionately high rate, real hot spots of tidal action,” Hill said. “One of these today is Hudson Bay, and it’s helping to reduce tidal energies all over the rest of the Atlantic Ocean. But during the last ice age Hudson Bay was closed down and buried in ice, and that caused more extreme tides elsewhere.”
Many other factors can also affect tides, the researchers said, and understanding these factors and their tidal impacts is essential to gaining a better understanding of past sea levels and ocean dynamics.
Some of this variability was suspected from previous analyses, Hill said, but the current work is far more resolved than previous studies. The research was done by scientists from OSU, the University of Leeds, University of Pennsylvania, University of Toronto, and Tulane University.
“Understanding the past will help us better predict tidal changes in the future,” he said. “And there will be changes, even with modest sea level changes like one meter. In shallow waters like the Chesapeake Bay, that could cause significant shifts in tides, currents, salinity and even temperature.”
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Remember as well that at the height of the last ice age, when Toronto and New York were under a couple of miles of ice, the ocean level was hundreds of feet lower than it is oday.
Add in isostatic adjustment and voila . . .
@Alan Bates says:
August 2, 2011 at 10:56 am
Prefer the Clifton Hotel myself.
Good also to see one of the industrial revolutions greatest inventions.
“Due to phenomena such as ice ages, plate tectonics, land uplift, erosion and sedimentation, tides have changed dramatically over thousands of years and may change again in the future, a new study concludes.”
What about close encounters with large celestial flybys?
That video is amazing! In all my years working on climate models I’ve never seen anything like that! – incredible how CO2 in the atmosphere can increase so sharply as to cause such a sea level rise, then abruptly fall to cause the sea level rise to be reversed – all over a 24 hour period.
We’ll need R Gates to explain for us how CO2 in the atmosphere can rise and fall so quickly – or maybe Steve Mosher!
Unrelated, but a funny story… a few years a we took the sailboat over to Charlottetown Harbour in Prince Edward Island, and tied up to the floating wharf at the marina. I jumped onto the wharf, then onto the grass and headed over to the bar for a cold beer or 2….about 4 hhours later I went back to the boat, and jumped back over the same spot where I came up, but little did I know there was an 8 foot drop ….yikes…luckily the floating wharf absorbed my fall and I was OK…but did not realize that PEI had such high tides….anyway, that is all I have..thanks
Ian
Interesting stuff – a variable more to feed into the models. Worse than …
Honestly: interesting to read every day about new little factors and impacts on climate and the state of nature that we see today. One issue more that might not be settled yet, but will be subject to further
study.
Best
Matt
One of my favorite places on Earth is Mont St Michel, France. The difference between high and low tide can be as much as 46 feet and it comes in as fast as a galloping horse. I think they will adapt, somehow.
In answer to a question about tidal variation over geological time, Dr Russ Evans of the British Geological Survey gives a short and interesting reply:
“Based on information obtained from tidal rhythmites, Williams (2000) showed that at 620Ma the Earth-Moon distance was 0.965 of its present value, and that at 2450Ma it was 0.906 of its present value. These and other considerations regarding the Earth-Moon system (Williams, 2000; Varga et al. 2006) lead to the conclusion that the distance between the Earth and the Moon was perhaps only 20% or so less than its current value even at the start of their joint evolution 4+ billion years ago. This appears to be the current consensus view amongst geologists working on this matter. Williams’ results also imply that the rate of recession of the Moon has accelerated over that period.
In terms of tides, if the Earth-Moon distance has never been more than ~20% less than the present value, then tidal forces have never been much more than 40% greater than current values. Since tidal heights today vary far more than this, from less than 1m in the deep ocean (and much less in confined seas such as the Mediterranean) to 17m in the Bay of Fundy, it seems unlikely that tidal heights, even at unusual locations such as Fundy, or at any point in the past, were significantly more extreme than those seen today.”
http://www.geolsoc.org.uk/gsl/pid/7680;jsessionid=EE00DDC5133976F27BBE2C2BC8E306BF
has this been discussed?
Quantitative Estimates of Warming by Urbanization in South Korea over the Past 55 Years (1954-2008)
Maeng-Ki Kim and Seonae Kim
1 Department of Atmospheric Science, Kongju National University, Gongju, 314-701, Korea
2 Applied Meteorology Research Team, Environmental prediction Research Inc., Daejon, 302-831, Korea
Received 20 October 2010; revised 8 July 2011; accepted 12 July 2011. Available online 23 July 2011.
Abstract
http://www.sciencedirect.com/science/article/pii/S1352231011007540
Re Bill Illis
The impact on past sea level reconstructions depends on the type of proxy used. Changing tidal range tends to be most important for indicators such as macrofauna and microfauna that occur at specific zones relative to the tidal elevations. For example, high salt marsh foraminiferal distributions have been used to reconstruct sea levels globally assuming a constant tidal range (see Scott et al, 1996, Journal of Coastal Research 12(4): 850-861 as background, or Google Scholar search for Gehrels, W.R. for more recent applications). These data would be impacted by changes to high tide elevations.
Note that the tidal ranges will also be impacted by sedimentation and dredging in estuaries, and hence complicate the interpretation of high salt marsh microauna.
The implication is that Hudson Bay is part of the Atlantic?–must have misspoken. There is a nice animation of various tidal components in the Canadian Archipelago, Arctic basin, Baffin Bay, and Hudson bay right here.. I have broadband wireless and it took a solid 30 seconds to load, but is very revealing. It looks like the Canadian Archipelago is the real dissipator, and this may have been inoperative with lower sea level 9000 ybp.
Sorry…the link for the whole suite of animations is here. My previous link took one only to one animation.
We live right on the bay of Fundy, and love watching the tides here. This is a link to a time-lapse video that one of my friends made yesterday at the harbour in Alma, New Brunswick.
The tide was roughly 28 feet at St. Johns New Brunswick back in the 1950’s. Not too certain what it is today.
“Understanding the past will help us better predict tidal changes in the future,”
What a crock! We can’t predict climate. We can’t predict tectonic plate drift and speed. We can’t predict catastrophic meteorite or comet collisions (except when relatively imminent). In fact, there’s little we can predict about what the earth and its atmosphere is going to do in the long run. Period. We can only measure the changes as they occur and adapt to them. As for the tides, the current tide charts are perfectly adequate for the present.
And the CO2 did what?
I think I missed something. What did the CO2 do to the tides over the last 20K years?
Don’t recall that Prof Mann, after all his putzing about in the shallows on the NC coast, looking at foraminifera, etc, ever mentioned anything about historic tide levels that might have impacted his study. Better reconcile that before he hears about this and brings down the wrath of CliSci on WUWT.
This is an interesting map.
http://en.wikipedia.org/wiki/File:M2_tidal_constituent.jpg
Check the tide change from Perth to the Kimberley in Western Australia.
Jack K wrote:
August 2, 2011 at 5:57 pm
The tide was roughly 28 feet at St. Johns New Brunswick back in the 1950′s. Not too certain what it is today.
Hi Jack-
I grew up in Saint John (kindly note that St. John’s is in Newfoundland, about 600 miles away). The daily paper (Telegraph-Journal) gives tides for six places around the province. The tide at Saint John today is around 8.2 meters / 27 feet. The range is around 24 to 28 feet, from memory. Googling could probably find all details.
IanM
Reading WUWT is fun. One never knows what locale will be discussed next. Today it was only a few miles from where I now live (twenty-odd miles up the St. John River from Saint John, which is at the mouth of the river). The tides are quite impressive. Mispec Beach, not far from SJ, offers several hundred feet of sand at low tide, all of which is covered as the tide comes in. Interesting even to residents.
Ian
@ur momisuglyRichard Dupuis Morcom,
I grew up in New Brunswick and enjoyed that time-lapse chronicle of yesterday’s high and low tide at Alma. For those here unfamiliar with N.B., Alma is the village that is adjacent to Fundy National Park, which if you like wilderness is well worth a visit, both for watching the tides (the water is unbearably cold) and for enjoying the sweet air and inland trails.
@ur momisugly Jack K.
The city in New Brunswick is Saint John (quite often written that way). St. John’s is the capital of Newfoundland. The tidal amplitude you mention sounds about right – but everything technical is measured in metres in Canada today, so it’s hard to confirm at a quick glance.
I once took at field course at the St. Andrews Biological Station/Huntsman Marine Laboratory at the mouth of the Bay of Fundy/Passamaquoddy Bay and well recall the admonition that we had to keep an eye on the waters. One day we were digging specimens from the broad swathe of mud flats adjacent to a road that joins Moose Island to the mainland at low tide (it is deep under water at high tide). I well recall the speed with which the tide came in. The water just simply starts coming towards you – not moved by wave action, and no going back and forth of the position of the front line of waters. It comes in at about 3 – 4 miles per hour at that location. We had to beat a hasty retreat once the tides had turned.
The information of the study:
Hill, D., S. Griffiths, W. Peltier, B. Horton, and T. Tornqvist (2011), High-resolution numerical modeling of tides in the western Atlantic, Gulf of Mexico, and Caribbean Sea during the Holocene, [i]J. Geophys. Res.[/i], doi:10.1029/2010JC006896, in press. [PDF] (accepted 15 July 2011)
I think little of models, but for the sake of argument, let’s take this one at face value. Following presented in the paper:
1. Hudson’s Bay dampens out tides and prevents them from becoming extreme.
2. Hudson’s Bay “damping” effects don’t work if ice blocks off the channels from the ocean.
3. Hence, cooling = extreme and violent tides. Warming = benevolent tides.
CONCLUSION
Cold bad. Warming good.
Did anyone else see that 3 mm rise at 41 seconds?
“The work was done with computer simulations at a high resolution”. Say no more. Simulations are fundamentally poor, they reflect the data entered, some real, some cherry picked. We can’t simply choose which models we like and don’t like. We need scientific proof, not hunches.