The tides they are a changin'

Scientists from the University of Southampton have found that ocean tides have changed significantly over the last century at many coastal locations around the world.

Increases in high tide levels and the tidal range were found to have been similar to increases in average sea level at several locations.

The findings of the study are published online in the journal Earth's Future.

It is well documented that global average sea levels are rising; but tide levels, have generally been considered to have undergone little change on decadal time scales. It is also often presumed that will not change much over the next century. As such, long-term changes in tides are not accounted for in many practical applications and scenarios affected by .

The team used a dataset of 220 sea level records from around the world, which ranged in length from 30 to 150 years. By extracting the tide data from the other components of sea level, they were able to isolate changes in 15 tidal levels by looking at different records of high and low waters from the tidal signal.

Lead author Robert Mawdsley, postgraduate research student in Ocean and Earth Science, says: "We find that at many sites around the world significant changes in tidal levels have already occurred, and at some sites the magnitude of the changes are comparable with the increase in global mean sea level through the 20th century. For example, increases in average high water of over one millimetre per year have occurred around the world, including Calais in France, Manilla in the Philippines, Wilmington in the USA and Broome in Australia.

"The magnitude and global distribution of changes in tides have been hinted at before," said co-author Dr Ivan Haigh, Lecturer in Coastal Oceanography. "However, here we have been able to assess changes in different tidal levels, which are used for many practical applications. Tides exert a major influence on the coast, affecting coastal flooding and erosion, navigation, tidal energy extraction, sediment movement and the extent of species in coastal ecosystems. Therefore, the changes we have identified have wider ranging practical and scientific implications, particularly if they increase in the future."

"The cause of these changes is complex and appears to be a combination of mechanisms from local to global, with the primary driver being the rise in associated with climate change," says co-author Dr Neil Wells, Associate Professor in Physical Oceanography and Meteorology. "Further research is required to more fully understand the mechanisms causing these changes and to understand how tides might further change in the future."


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More information: Robert J. Mawdsley et al., "Global Secular Changes in different Tidal High Water, Low Water and Range levels," Earth's Future, DOI: 10.1111/eft2.2014ef000282
Citation: The tides they are a changin' (2015, March 5) retrieved 24 August 2019 from https://phys.org/news/2015-03-tides-changin.html
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Mar 06, 2015
They did a study to find out that the tides would be higher as the sea levels rise? That must be a nice job. I live in Wilmington and could have told them that without the study. Our high tide line has been getting higher on the beach for the last 30 years that I know of personally.

Mar 06, 2015
The obvious answer, since we think we control everything, is to detonate a thermonuclear device in space between us and the moon, increasing the distance between us and negating the tidal effects.

Mar 06, 2015
The obvious answer, since we think we control everything, is to detonate a thermonuclear device in space between us and the moon, increasing the distance between us and negating the tidal effects.

You think that is an answer? Aren't you the same person who said this:
Thank you {howhot2} for demonstrating your maturity level. Gotta say I'm disappointed with some of the posters in a supposed scientific forum.
Pot, meet kettle?

Mar 06, 2015
Did you feel directly insulted by my comment?

Mar 06, 2015
Jeff: I don't know how Magnus will answer but my answer is that this is a serious question. For decades people have been modeling tides and rising sea levels, but it has been difficult to make the measurements that are needed to validate models. The first of the direct measurements are coming in and you are sitting there wasting bandwidth with a stupid comment about detonating a nuke as an answer. What this shows me is that there is a good chance you have discounted the chances of serious flooding from high tides. If you have never been in a serious flood before, I recommend you move to Florida and wait...

Mar 06, 2015
Did you feel directly insulted by my comment?


It was intended to be insulting and condescending. So yes.

Mar 06, 2015
Any day that evil CO2 will cause the sky to fall.

Mar 06, 2015
Study is accessible online here. The eccentricity of Moon orbit also increased in recent time with speed 3.5 mm/year. I speculated about global warming effects of dark matter at the galactic plane, which is pervading the solar system like the sparse gas and increasing density of vacuum into account of matter. In more dense vacuum the gravity of of massive bodies would weaken and its geometric effects would be more pronounced... But can such an minute effects explain the easily observable trend in tides? IMO the increased area of flooded shelf is the main culprit here.

Mar 06, 2015
Feel free to correctly me if I am wrong but the sea rise each year is about 3mm or the thickness of 2 US one cent pieces. Also the rate of rise is declining. This is much ado about nothing since the seas have been rising since the melting of the glaciers.

It is just human hubris to build your house in a swamp and complain when your feet get wet.

Mar 06, 2015
Feel free to correctly me if I am wrong but the sea rise each year is about 3mm or the thickness of 2 US one cent pieces. Also the rate of rise is declining. This is much ado about nothing since the seas have been rising since the melting of the glaciers.

It is just human hubris to build your house in a swamp and complain when your feet get wet.


You know me, I am always ready to correct. The issue is that sea level rise is not uniform (as I am sure you know). It is also not expected to be linear.

http://tidesandcu...nds.html

As you can see there is no simple trend and some areas are expected to be 3 - 7 feet deeper. However, everyone that writes on the subject seems to acknowledge that the Greenland ice sheet and the Antarctic ice sheets are the wild cards. However, even if they go up 3 feet by 2100 this heating won't stop for hundreds of years and the surface can continue to rise during that time.

Mar 06, 2015
I guess I take a very practical/philosophical approach to this. When the oceans rise, when tidal or storm flooding happens too frequently in a community, we move away from the shoreline. It was our mistake to assume that shorelines were static and build "permanent" structures there. But we're learning. If it weren't for all the money we threw into infrastructure with the expectation that it would be there forever, this wouldn't even be a problem. I think some of us are just going to get a tough lesson in impermanence.

Mar 07, 2015
The climate changes.

Since the beginning of time.

So, what?

"The polar bears well be fine." - Freeman Dyson

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