What conditions do we need for our Rivers to Freeze?

Hi weather thread folk!!!


What conditions do we need to freeze flowing water?
I have seen photos of the Liffey at Lucan weir frozen over - this is rare I believe? How rare? How cold does it need to be? Weather patterns etc?

Keep it Real!

Villain

Well I'm not certain of the exact conditions but if you google Winter of 1962/1963 you will probably find the info you need as I believe that is the last big freeze which saw the Thames and other rivers freeze.

Thanks, will do

http://www.metoffice.gov.uk/education/secondary/students/winter.html
if anyones interested:

In mid January 1947, no-one expected the winter to go down in the annals as the snowiest since 1814 and among the coldest on record. After two cold spells that had failed to last - one before Christmas 1946, the other during the first week of January - the weather had turned unseasonably mild.

During the night of 15-16 January, the temperature at Leeming in North Yorkshire didn't fall below 11.7 °C. The following day, maximum temperatures close to 14 °C were recorded in Norfolk, Herefordshire and Flintshire. All this was soon to change.

An area of high pressure moved northwards from France on 18 January. Two days later, the anticyclone was centred off north-west Norway. It then drifted south-east to southern Scandinavia, and dominated weather over the British Isles for the rest of the month. The first night frost came on the 20th and the winter began in earnest on the 23rd, when snow fell heavily over the south and south-west of England. Even in the Isles of Scilly, a few centimetres of snow fell. The blizzard in south-west England was the worst since 1891; many villages in Devon were isolated.

Pherekydes

In 1986 the River Slaney froze along its edges. This was in the Glen of Imaal where the river is quite fast flowing. It was a bit nippy!

I see 1982 isn't given a mention on that link. The "Big Snow"...

lucernarian

I thought that the lowest ever recorded temperature in the British Isles was in Scotland in January 1982. That time period should have seen some recognition. January 1979 was also pretty severe, though shorter in intensity.

A Dub in Glasgo

The lowest temperature recorded was in Scotland on 3 seperate occasions

-27.2°C Braemar 11/02/1895 & 10/01/1982
-27.2°C Altnaharra 30/12/1995

It was during that Christmas - New Year cold snap in 1995 that I crossed the Jamaica Street bridge over the River Clyde in Glasgow city centre and the river was frozen

Trogdor

I was just thinking if there is a lot of heavy snowfall, with the cold snow falling into the river would it rapidly cool the river hence helping it to freeze over?

billy the squid

http://www.boards.ie/vbulletin/showthread.php?t=2054850822

Some images of a frozen River Shannon at Limerick can be found there

The pictures were taken in 1963

Snowbie

trogdor wrote:

I was just thinking if there is a lot of heavy snowfall, with the cold snow falling into the river would it rapidly cool the river hence helping it to freeze over?

It gives it a false ice impression.If you think of it,continuous heavy snow over lets say an inland body of fresh water.If the top layer of water is not frozen already by the cold temps,the snow will give a type of slush effect at first and accumulate depending on if this is a continous snow event.It will therefore look frozen with a covering of ice untill you step on it and get very wet and hypothermic.The snow will chill the air above it making it look white and frozen while it acts like a blanket keeping the underside in a liquid state.
As is the case if snow falls on a pavement the warmer part of the snow accum is always the bottom layer while the top generally is frozed and compacted.

Remember water freezes at approx 0c while sea/salt water freezes at about -8c.So obviously it would take an extreme cold event to cool our coastal waters in our bays to form sea ice.

yeah but is it or is it not harder to cool moving water to freezing point? i.e -1 air temp will give ground frost but wont freeze rivers (maybe it would if it was -1 continuously for long enough? yes? No?)

Snowbie

I stated in the above post as an inland body of water ie:lake.It would be nearly impossible to freeze a moving body of water at air temps -1c.
At -1c air temp doesnt mean that water temps be -1c.Water holds heat much better than air does.To get water to freezing point to film freeze on top i expect air temps to be consistently at -5c or lower over consectutive days during nighttime and not above 0c by day.By then ice would thicken and broaden from the edges.The deeper you go in water temp increases.So if its 0c water temp at surface it could be 4c only 6ft down.

Moving water would create more friction and latent heat and must be much much colder for it to totally freeze over.