Raising the Barrier

[pugwash]

Today's Telegraph reports that while the Thames Barrier was raised once a year about a decade ago, but last year it was raised six times. Another report elsewhere says the barrier has been raised 24 times in the last two years.

In light of this, higher tides and flooding threats must be significiant. Do you East Coast mud-wallopers notice changes? Are you buying higher gumboots? Is the water getting into your cars parked at the marina? What's going on?

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[celandine]

Havn't noticed higher tide levels here on on the next-door (and much nicer) River Medway. If they are raising the Barrier more often I would suspect that it is someone who wants to keep his job trying to look busy. They can do this more often these days without disrupting commercial traffic because, compared with a decade or so ago, there isn't any.
However, ever since they built the Barrier, the more alarmist thinkers here on the Medway, have wondered whether if the tidal surge is blocked from going up the Thames, will it come surging even more up the unprotected Medway. So my view is that the Barrier should never be raised under any circumstances since it might put the village of Lower Rainham at risk - or am I being a bit parochial.

Mick

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[boatmike]

Hate to be negative but a recent programme on local TV said the waters are rising nationally and the salt marshes in the eastern solent would be underwater in 10 years.... Global warming? Ice caps melting? Dunno......
Anyone got any statistics on this?

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[Tezza]

Sorry - but you did ask for statistics... the generally accepted position is that sea levels will rise by about 0.5m in the next 100 years (OK I won't be around either). As you suggest this is due to global warming estimated to be around 3oC over the same period. What's interesting is most of the sea level rise is due to the thermal expansion of the oceans - not ice melting - in fact if the Antarctic ice melts the sea levels go down as the melted ice displaces less.

Quite a dry fact ridden effort for my maiden posting!

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[boatmike]

A sobering thought Tezza.... I shall be 161 years old then so probably not be too interested but perhaps I will sell my house on the sea front at Lee-on-Solent before I pop my clogs and bequeath my boat to my kids.......
Thanks for the "not so dry" statistics.......

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[Parsonsheath]

Don't sell your house "on the front", there is enough problem getting a mooring now, let the kids and grandkids keep the land , once it is flooded it will be worth ten times as much as a site for a new marina!

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[roger]

With the barrier there are two factors working together; sea level rise and tilting Britain. The tilt is due to the "rebound" of
Scotland etc. after the weight of the icecap during the last ice age depressed it. Now the ice has gone the tilt is being corrected. According to a recent TV programme this also accounts for the Solent. The too is of pretty recent date. The Isle of Wight was joined to the mainland.
The effect is even more obvious at the west end of Finland. In the Aaland islands the oldest settlements are at the tops of the islands and they gradually migrated down the hills as the water retreated.
They are going up and London and the Isle of Wight is going down.
The Thames Barrier has a comparatively short expected life. As London sinks it will get less effective. It'll probably outlive me but it'll be quite soon that someone will have to start thinking up a replacement.
To veer from the topic a bit - it's apparently not a good idea to close the barrier quickly - think of water hammer on a very large scale!!

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[JMM]

Surely most of the Antartctic ice is on land . . . this melting would raise sea levels considerably!

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[OzGirl]

And why should the melted ice displace less? Archemedes and all that

(ps I am not the sharpest chisel in the tool box when it comes to things mathmatical /forums/images/icons/laugh.gif)

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[Tezza]

Mmm - both JMM and Ozgirl have a good point. If the entire Antarctic ice sheet were to melt we would be in serious doo-doo. However, the question is much more complex and it seems like the balance of scientific opinion is that a moderate rise in global temperature will result in a negative contribution to sea levels from Antarctic ice.

If you want to know more see…

http://yosemite.epa.gov/oar/globalwarming.nsf/UniqueKeyLookup/SHSU5BPJU5/$File/chapter_5.pdf

It’s given me a headache trying to understand it!


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[BrendanS]

The volume of floating ice is subtracted from total volume of ice (giving grounded volume), so it's only the net additional volume that is calculated

for calculations in a previous thread <A target="_blank" HREF=http://www.ybw.com/cgi-bin/forums/showflat.pl?Cat=&Board=ym&Number=429161&page=&view=&sb=&o=&vc=1>here</A>

<hr width=100% size=1>There is no such thing as "fun for the whole family."

 

[IanPoole2]

On the Colne - it's not so much rasing sea levels that have been noticed, but excessive silting up.

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[pugwash]

Exactly. The Isle of Thanet is now part of the mainland. The Cinque ports are silted up. This suggests land is rising or water level is decreasing, which is in keeping with the rebound theory. So why would London be sinking (unless it's simply rotten to the foundations, as might be the case)? As far as I know, the rise of sea level due to global warming is immeasurable except in a general way.

The Antarctic is not just an ice sheet. It is basically an ice cap (on dry land) surrounded by ice sheets of which some are aground. These behave in different ways. On one side of the continent the ice sheets are breaking up and drifting away, but on the other they are accumulating.

The reason sea level may fall as the world gets warmer is that the sea produces more water vapour that falls on Antarctica and is locked up as ice for thousands of years. That's a theory I heard at the Scott Polar Research institute, but the scientist told me that sea level was also affected by all sorts of local factors not to mention cycles. For instance, the sheer mass of Antarctica has the effect of sucking the surrounding the sea towards itself and raising its height by significant amounts.

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[jimi]

And also I suppose cos its down the bottom, the sea will tend to naturally drop down towards it?

<hr width=100% size=1>.. whit way roon should it be again ..

 

[pugwash]

Right, just like Scotch pours upwards...

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[BarryH]

Your almost right, but what every one has over looked is you lot. Now as I see it we can use a bit of skoolboy science here. Remember that gezzer, the greek bloke, that shouted Eureka!! Everyones forgot about him and what he found out jumping into a bath. Oh ho! I hear you cry. The lads got something there. uh huh, yeah see. The reason the sea level has risen is because they let too many keeled boat into the marinas in Southampton. So for the Thames Barrier to become redundant we all need to take our boats out of the water!!

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[jimi]

Makes you wonder what would happen if all the compressed air devices were released .. all tyres, blow up rubber dinghies, dolls,sheep, oxygen cylinders,tins of beans etc

<hr width=100% size=1>.. whit way roon should it be again ..

 

[Twister_Ken]

Silly Billy

But if we lifted our boats from the water, we'd have to put them on the land - which would make the land heavier, thus sinking it and therefore - apparently - raising sea level.

Anyway, yer average Benjenbav floats on a wet tissue and don't make a decent sized dent in the water.

<hr width=100% size=1><A target="_blank" HREF=http://www.writeforweb.com/twister1>Let's Twist Again</A>

 

[BarryH]

Re: Silly Billy

Now your just being picky!

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[boatmike]

So let me get this straight.
Scotland is going up cause it was depressed before.
All the depressed scots are moving to the Solent and their combined weight is pushing my house underwater.
Now I'm depressed.
Just heard we won't get anymore asylum seekers in Lee-on-Solent (whoopee!) and now I find it's all Jimi's fault....
Is that right?


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