First ECSKA paddle of the new year Sat 9th from Bullock Hbr.
You have a lie-in -
we will start at 10:30 after Alan\'s Strokers clinic. :whistle:
There may be some wind so dress well.
The good news is that sea water temp is over 7 degrees !
An update will be posted later, for your encouragement.
MPOF
ECSKA Paddle Sat 9th - Bullock
Re:ECSKA Paddle Sat 9th - Bullock
Confirming that tomorrow morning\'s paddle will start at the slightly later time of 10:30 from Bullock hbr.
We may get snow but I don\'t expect ice.
Although I have heard of ice forming on Galway bay - explain that Knotman!
Keep warm,
MPOF
We may get snow but I don\'t expect ice.
Although I have heard of ice forming on Galway bay - explain that Knotman!
Keep warm,
MPOF
Re:ECSKA Paddle Sat 9th - Bullock
Mick, a chara. Possibly some fresh water floating on more dense seawater, would be my guess at the moment. God knows, too much of that around at the moment.
Teelin Bay in Donegal, after a big big rain, often has the fresh brown bog water floating on the clear sea water, for quite a distance out of the bay, sometimes to a depth of 2 feet. Divers are pleasently surprised, on bieng dropped into murky brown water, to suddenly find a clear dive a few feet down. I\'m sure there are many other bays which exhibit such behaviour. Sennen
FREEZING SEA WATER. (Copied, not mine!)
The density of ocean water is determined by its salinity (or salt content) and temperature. The saltier and/or colder the water is, the denser it is. Salt water is most dense at its freezing point, unlike fresh water, which is most dense at about 3.9°C (39.0°F). Oceans are highly stratified: deep ocean water is heavy, and the lighter water is on top. This often is not the case in the atmosphere: warm air near the ground surface is lighter than the overlying air it displaces, resulting in unstable conditions and thunderstorms.
The stratified, stable nature of oceans is important because otherwise there would be no sea ice , nor would there be warm tropical seas. Tropical oceans are temperature-stratified: a thermocline separates the warm, light water on top from the frigid deep waters. Polar oceans, on the other hand, are salinity-stratified: the salinity is slightly lower on top, especially in the Arctic and near the estuaries of large rivers such as the MacKenzie in Canada and the Ob in Russia. This fresh-water outflow will stay on top of the Arctic Ocean and mix only very slowly, because it is lighter. Instead of a thermocline, there is a halocline, a layer in which the salinity changes rapidly with depth.*
Salty water freezes below 0°C (32°F): this is why salt is used to melt the snow or ice on a road pavement. The saltier the brine , the lower its freezing point. This is also why salt traditionally was added to the water–ice mixture used to make ice cream.
Ocean water with a typical salinity of 35 parts per thousand freezes only at −1.8°C (28.9°F). So if there were no halocline in the polar oceans, then the cooled top ocean layer, being denser, would sink into the deep ocean, in the same way as thunderstorm clouds rise in the atmosphere, and the entire ocean column would have to cool to −1.8°C before its surface could freeze.
Formation of Sea Ice
As sea water freezes, salt is excluded, because salt has a different crystalline structure: it forms cubic crystals (with four sides) whereas ice is hexagonal, or six-sided. (A close look at tiny snowflakes will reveal their hexagonal form.) So pockets of brine form within the ice; they refuse to freeze, because of the high salinity. The brine then slowly leaches out of the bottom of the forming ice and drips into the ocean below. Thus sea ice, when melted, is considerably fresher than the original sea water from which it formed. This brine rejection process creates dense water below the ice surface. This layer of dense water may sink to the bottom of the ocean. Furthermore, this process of \"deep-water formation\" is an exception to the normally stratified nature of oceans.
The salt enrichment is most effective when it occurs in a thin layer on a calm sea. The faster sea ice is frozen, the less salt that can escape. For instance, when frozen at an air temperature of −40°C (−40°F), the salinity of the ice is about 10 percent. But when frozen at an air temperature of −6°C (21°F), the salinity of the ice is only about 4 percent. Such ice is fresh enough to use as drinking water; in fact, in spring, polar bears often drink the water in melting ponds on ice.
When sea ice melts in the summer, the meltwater forms a relatively fresh surface layer that lies above the saltier ocean water, maintaining the halocline, and allowing easier freezing the next winter.
Teelin Bay in Donegal, after a big big rain, often has the fresh brown bog water floating on the clear sea water, for quite a distance out of the bay, sometimes to a depth of 2 feet. Divers are pleasently surprised, on bieng dropped into murky brown water, to suddenly find a clear dive a few feet down. I\'m sure there are many other bays which exhibit such behaviour. Sennen
FREEZING SEA WATER. (Copied, not mine!)
The density of ocean water is determined by its salinity (or salt content) and temperature. The saltier and/or colder the water is, the denser it is. Salt water is most dense at its freezing point, unlike fresh water, which is most dense at about 3.9°C (39.0°F). Oceans are highly stratified: deep ocean water is heavy, and the lighter water is on top. This often is not the case in the atmosphere: warm air near the ground surface is lighter than the overlying air it displaces, resulting in unstable conditions and thunderstorms.
The stratified, stable nature of oceans is important because otherwise there would be no sea ice , nor would there be warm tropical seas. Tropical oceans are temperature-stratified: a thermocline separates the warm, light water on top from the frigid deep waters. Polar oceans, on the other hand, are salinity-stratified: the salinity is slightly lower on top, especially in the Arctic and near the estuaries of large rivers such as the MacKenzie in Canada and the Ob in Russia. This fresh-water outflow will stay on top of the Arctic Ocean and mix only very slowly, because it is lighter. Instead of a thermocline, there is a halocline, a layer in which the salinity changes rapidly with depth.*
Salty water freezes below 0°C (32°F): this is why salt is used to melt the snow or ice on a road pavement. The saltier the brine , the lower its freezing point. This is also why salt traditionally was added to the water–ice mixture used to make ice cream.
Ocean water with a typical salinity of 35 parts per thousand freezes only at −1.8°C (28.9°F). So if there were no halocline in the polar oceans, then the cooled top ocean layer, being denser, would sink into the deep ocean, in the same way as thunderstorm clouds rise in the atmosphere, and the entire ocean column would have to cool to −1.8°C before its surface could freeze.
Formation of Sea Ice
As sea water freezes, salt is excluded, because salt has a different crystalline structure: it forms cubic crystals (with four sides) whereas ice is hexagonal, or six-sided. (A close look at tiny snowflakes will reveal their hexagonal form.) So pockets of brine form within the ice; they refuse to freeze, because of the high salinity. The brine then slowly leaches out of the bottom of the forming ice and drips into the ocean below. Thus sea ice, when melted, is considerably fresher than the original sea water from which it formed. This brine rejection process creates dense water below the ice surface. This layer of dense water may sink to the bottom of the ocean. Furthermore, this process of \"deep-water formation\" is an exception to the normally stratified nature of oceans.
The salt enrichment is most effective when it occurs in a thin layer on a calm sea. The faster sea ice is frozen, the less salt that can escape. For instance, when frozen at an air temperature of −40°C (−40°F), the salinity of the ice is about 10 percent. But when frozen at an air temperature of −6°C (21°F), the salinity of the ice is only about 4 percent. Such ice is fresh enough to use as drinking water; in fact, in spring, polar bears often drink the water in melting ponds on ice.
When sea ice melts in the summer, the meltwater forms a relatively fresh surface layer that lies above the saltier ocean water, maintaining the halocline, and allowing easier freezing the next winter.
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dermotfinn
- Posts: 0
- Joined: Sat Oct 26, 2013 9:37 am
Re:ECSKA Paddle Sat 9th - Bullock
Some photos of the Bullock to Dalkey (9th January 2010) trip here
Post edited by: dermotfinn, at: 2010/01/10 21:11Post edited by: dermotfinn, at: 2010/01/10 21:12
Post edited by: dermotfinn, at: 2010/01/10 21:11Post edited by: dermotfinn, at: 2010/01/10 21:12
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conorsmith
- Posts: 206
- Joined: Sat Oct 26, 2013 9:37 am
Re:ECSKA Paddle Sat 9th - Bullock
I have a couple of photos from a paddle in Kinvara Bay this afternoon - see topic Westie Paddle Sunday 10th Jan. An area within the bay itself had surface ice up to approx 100 yards out from shore and at least 2mm thick on the outer edges.
A couple of very very small streams flow into the bay, but nothing major. We had no significant snowfalls to accumulate on low tide to freeze and subsequently lift and I can only assume ice formed from temperatures falling below -6 over last couple of nights?
Fascinating to see though and something I did not expect to come across along our coastline, particularly on the Atlantic side.
The area you see in front of the boat had a complete covering of a single ice sheet, and right to the shore. This does not dry out at low tide.
[img size=600]http://www.irishseakayakingassociation. ... 100164.jpg[/img]Post edited by: conorsmith, at: 2010/01/10 23:22
A couple of very very small streams flow into the bay, but nothing major. We had no significant snowfalls to accumulate on low tide to freeze and subsequently lift and I can only assume ice formed from temperatures falling below -6 over last couple of nights?
Fascinating to see though and something I did not expect to come across along our coastline, particularly on the Atlantic side.
The area you see in front of the boat had a complete covering of a single ice sheet, and right to the shore. This does not dry out at low tide.
[img size=600]http://www.irishseakayakingassociation. ... 100164.jpg[/img]Post edited by: conorsmith, at: 2010/01/10 23:22
