Freezing and thawing

The tidal inlet on the cold morning of December 9th
The tidal inlet on the cold morning of December 9th

The temperature has been bouncing around like a yo-yo – rather like the price of gas, from minus 10 degrees C to plus 10 and back again within a few days.

Unlike fresh water, which is at its most dense around 4 degrees C, salt water is most dense at its freezing point, which is typically around minus 2 C.  The more salt is in the water, the lower its freezing point.  In oceans that freeze, the water deeper down is saltier, so it stays down, and is less likely to freeze because the high salt concentration lowers its freezing point considerably.  The lighter, relatively fresher water stays on top – so it’s more likely to freeze, and when it does freeze it has little salt in it, as I found out by tasting it.

Ice that formed over rocks at high tide, then bent and cracked as the tide fell.
Ice that formed over rocks at high tide, then bent and cracked as the tide fell - December 14.

Ice on the water’s edge on Mahone Bay

The water's edge, tide rising after a cold night
The water's edge, tide rising after a cold night
The ice that was shaped by this rock and then broke as the tide fell tide now floats over it on the rising tide.
The ice that was shaped by this rock and then broke as the tide fell tide now floats over it on the rising tide.

I tasted the ice that had formed at the water’s edge on a small beach, as I said I would. As predicted, it was indeed fresh, not salty.  A good survival tip, should you ever find yourself shipwrecked on a desert island in winter.

Hatfield encounters a sticky oil spill

Canada’s Derek Hatfield hit an oilslick at 16 knots today, and it washed over the boat making a big mess. Now he has to clean up while still trying to make up for time he lost at the beginning of the race due to equipment problems.  At least he’s not dead last anymore in the Vendée Globe round the world solo yacht race.  But imagine the hazard of a slimy, slippery deck when you’re already pushing the limits.

Rooting for Derek Hatfield

We should all be wildly cheering on Derek Hatfield in his Algimouss Spirit of Canada, 60 foot speed machine, who is sailing alone around the world in the Vendée Globe race. He’s been running a bootstrap operation without the advantages of staff and money that a major sponsor would provide, but with the support of thousands of Canadians. Why isn’t there a daily update in a box on the front page of the Halifax Herald? Check out his site at SpiritOfCanada.net and the Vendée Globe site.

Ice on salt water

Ice crystals forming
Ice crystals forming

People are sometimes surprised to learn that ocean water can freeze (but think about it: we’re worried about the melting polar ice cap).  Two winters out of the last four, we’ve been able to skate on Mahone Bay after a really cold snap.  Salt water freezes at a lower temperature than fresh water, and the saltier it is, the colder it has to be to freeze.  I’ve found that it has a softer quality than freshwater ice, perhaps because of the impurities it would contain.  But I’m sure it’s just as unforgiving if you crack your head on it!

I’ve always found crystals fascinating. In my days as a lab chemist I enjoyed doing crystallization, which is done in the lab as a means of purifying a substance.  That’s because a crystal is formed when the molecules of a substance lock together in a close pattern.  There isn’t much room for anything else in there, between the molecules.  Separate the crystals from the rest, and you’ve got a pretty pure product.

Ice on a rock as the tide recedes
Ice on a rock as the tide recedes
This morning there were water crystals forming in quiet corners of the bay.  They are supposed to contain very little salt.  (Next time I’ll try tasting some!)  When salt water freezes on the surface, the ice is relatively fresh (i.e. not salty).  Polar bears are observed (not in Nova Scotia!) drinking from puddles on ice floes.  Meanwhile, the water beneath the ice gets saltier – and denser, sinking – which makes it even less likely to freeze.

Of course, these ice crystals I saw this morning melted during the day.

Watching the changes in the ice on the bay is one of the joys of living in Nova Scotia in winter.

If you want to read more about the science of seawater freezing, see the Water Encyclopedia.

Ducks eating on marsh at high tide

What are the ducks eating?
What are the ducks eating?

I wonder what the ducks are finding to eat in the flooded marsh? At high tide, a dozen of them will be gathered around one spot, head and neck down in the ooze.  Is it some small semi terrestrial creature that gets flooded out when the tide is so high?  Does anyone know?

Solar powered snow removal

Almost gone

It was a joke in the editorial cartoon of the Herald – a comment on the slowness of HRM to remove snow from the streets, but it sure worked in our neighbourhood. The foot of dense heavy snow that fell on the weekend disappeared in a couple of days.  High winds early in the week helped a lot too.  The Annapolis Valley had at least twice as much snow to go.  There were flood warnings in some areas.

It feels like spring!  🙂

Ducks

Pair of bufflehead ducks
Pair of bufflehead ducks

On my walk this morning, I saw no fewer than three species of duck in the little inlet taking shelter from the gale force southeasterlies: the American Black Ducks that breed prolifically around here, Mallards, and a pair of cute little Buffleheads.

Lobster season starts in southwest Nova Scotia

After what will surely be remembered as the great November snowstorm of 2008, I went for a walk this morning in crystalline -8 degrees(C).  From Crandall Point I looked out on the still waters of Mahone Bay, the open ocean behind, and counted six boats between Oak Island and Tancook.  I thought of our sailboat, now snug and dry, and marveled at the fishermen who brave such cold. But it’s the first day of lobster season, too important a day to stay home if you have traps to set.