Monday, October 24, 2016

Coolin' it #phenology

This morning there were many thirsty, frustrated young birds trying to figure out why they couldn't drink the clear (frozen) water in the bird bath. By 11 am or so it was still mostly ice-covered. That's when I plugged in the heater that should keep it from freezing all Winter, although it also makes it obvious how quickly unfrozen water evaporates in dry, below-freezing, air.

frozen bird bath with oak leaves
frozen bird bath with oak leaves
Photo by J. Harrington

Now we've reached the time to start watching morning mist/fog accompany heat loss from our local lakes and ponds. Soil-freeze is probably six to eight weeks away. Ice-up on larger lakes? Your guess is as good as, or maybe better than, mine. Local lakes should experience turnover, when the water is  briefly the same temperature from top to bottom, about this time of year. Then, cooler water will sink until it gets colder than 39 degrees, at which water is the most dense. I'm still trying to get my head around global warming versus La Nina for the upcoming Winter. We're expecting rain, not snow, tomorrow, for which I'm grateful.

In her Nature Anatomy, Julia Rothman offers a useful definition of a pond as
"a body of standing water too small
for significant waves or depth-based
temperature variations."
Lake Superior from Minnesota
Lake Superior from Minnesota
Photo by J. Harrington

Unfortunately, due, I'd guess, to space limitations, she doesn't elaborate on the depth-based temperature variations and how they change seasonally in lakes. Even a lake as large as Superior undergoes stratification and turnover. I used to be much more familiar with the details and timing of turnover, ice-in and ice-out when we lived on Big Carnelian Lake, but that was many years ago. Knowledge seems to be one of those things that comes under the heading of "use it or lose it."

Thin Ice

Reedy striations don’t occlude the beneath—
earthy mash of leaves, flat pepper flakes, layered,
tips protruding, tender-desolate above a mirror
surface, gently pressing on horse-mane, nest material,
tickle-brush, fringe. Buff block-shapes further down,
ghost-bits of green-green, a lone leaf burned white.
My thrown stone skitters on ice. The next, larger,
plunks through and for a moment I am a violator
but then I see it opened a bubble cell, a city,
a lesion, a map—the way in cold and luminous.


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