On our walk to the park last Friday, I noticed that Indian River had essentially no ice in it. Given the extreme (for here) cold we had been feeling for the past several days, I was a bit surprised by this.

By comparison, last year after a few days of freezing temperatures that were not nearly as cold as this year’s, the river was nearly completely covered in ice at the park.

I heard from someone who hiked to Indian River Falls this week, and he said there was no ice on the river until after the first bridge – after which the river was almost entirely iced over. I have previously noticed this (at the time unexpected) ice distribution on Indian River and realized that the west fork of Indian River runs warmer and does not freeze. This is due to the fact that not far above the confluence, the entire flow of the river is underground in normal-low flow conditions.

My guess is the flow from the west fork this year is warmer than during the cold snap last year (it could also just be putting more volume out, taking that much longer to cool off to freezing, but the water levels didn’t seem that much higher to me). A plausible explanation might be the warmer and much wetter weather that occurred in December this year relative to last year. Perhaps this influx of relatively warm water takes a while to move through the ground, so the pulse of warmer water was still flowing even after a week or more of cooler weather.

A couple of questions come to mind that wouldn’t be that hard to collect data for: How do the west fork and the falls fork of Indian River compare in temperature over the course of the year. How fast does the river cool off moving down stream in cold conditions? The best way to answer the first question would be to place a couple of ibuttons in waterproof enclosures just up from the confluence along each fork of the river. (The trick would be getting them secure enough to avoid losing them in high water.) Probably the second question would be best looked at by actually measuring in several locations along the river during a cold snap.

Walking to class this afternoon I stopped and took pictures of ice in various configurations.

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Conditions at Swan Lake were a bit slushy on top of old ice before the temperature dropped. Several sets of bird tracks were then frozen in the ice.

Conditions at Swan Lake were a bit slushy on top of old ice before the temperature dropped. Several sets of bird tracks were then frozen in the ice.

Conditions at Swan Lake were a bit slushy on top of old ice before the temperature dropped. Several sets of bird tracks were then frozen in the ice.

Pancake ice accumulated in the cove and was stranded by the falling tide.

Pancake ice accumulated in the cove and was stranded by the falling tide.

Pancake ice accumulated in the cove and was stranded by the falling tide.

Pancake ice accumulated in the cove and was stranded by the falling tide.

The kids and I hiked up Indian River Valley to visit the icy cliffs along the lower slopes of Verstovia.

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Looking down toward the estuary from the Totem Park bridge, Indian River is mostly iced over to salt water.

Looking upriver from the Totem Park Bridge, Indian River is mostly iced over.

Rowan thought this icicle was pretty neat and wanted me to take a picture of it.

This grove of decent-sized spruces stands out in part due to its lack of understory shrubs.

Connor is making his way up the steep slope to the base of the ice formations.

Connor and Rowan at the base of the ice-covered cliffs.

Connor and Rowan at the base of the ice-covered cliffs.

Connor and Rowan at the base of the ice-covered cliffs.

Connor and Rowan at the base of the ice-covered cliffs.

Connor and Rowan at the base of the ice-covered cliffs.

Icy cliffs on the lower slopes of Mt. Verstovia.

Rowan wanted me to take a picture of this chunk of ice she found.

This survey marker was not far from the cliffs.

Connor sits next to a pile of spruce cones, no doubt collected by an industrious Red Squirrel (Tamiasciurus hudsonicus).

Connor and Rowan taking a break on a rotting log in the spruce grove.

Swan Lake has remains almost completely frozen at the end of March. Since it first froze over in early December, it has not opened up significantly.

Although spring officially started last weekend, the winter weather continues to hold on, with snow falling most days last week and snow in the forecast through at least Friday.

Winter did not seem especially cold overall, but unlike many years, there was no extended period of above freezing temperatures. Swan Lake remains almost completely frozen, as it has since ice first formed by mid-December.

Despite the on-going wintery weather, there are signs of changing seasons. The herring have returned along with the many birds and marine mammals that feed on them, buds are swelling on many plants, and of course there is much more daylight. Last week I noticed a male robin that I suspect is an early migrant.

Thin ice covered a substantial part of Swan Lake around the edges.

It has been chilly the last couple of days, with partly cloudy skies overnight, but I still was a little surprised to see how much of the surface of Swan Lake was covered in ice. It was thin ice, though Mallards were able to land on it without breaking through. At this rate, perhaps it will be another winter like last, where the lake froze up at the end of November and never completely thawed until at least March or April.

Stems of Yellow Pond-lily (Nuphar polysepala) stick through the ice at the edge of Swan Lake.

Last February after a cool calm night, I took a morning walk to Totem Park and was interested to find that most of Crescent Bay was covered in ice. Salt water is supposed to freeze at 26F, and overnight lows probably got a little bit below that, but it was hardly frigid. Temperatures on other occasions have certainly been cooler without the extensive ice on the water that was present on this day.

The ice seemed to extend out beyond the islands called The Twins.

When I arrived at the end of the park, I was able to see the ice extended all the way out to Eastern Channel, though I could not really tell how far out into the channel it went. On the other hand, I discovered that Indian River estuary had no ice in it at all. Given the fact that salt water requires colder temperatures to freeze, this seemed a little strange.

After some thought I decided the key to this mystery must be the calm clear night. I think the there was probably very little movement of surface water in the bay overnight. Clear skies allowed the surface to cool quickly, and since there was little or no mixing (perhaps partially facilitated by a freshwater lens on the surface?), the surface was able to freeze. In principle this would seem little different than making ice in the desert by digging a hole and placing an insulated pan of water in it that is exposed to the night sky. Presumably the reason the river/estuary did not freeze is the water was flowing and the resultant mixing prevented the surface from getting cold enough to form a layer of ice.

Despite the frozen bay, Indian River Estuary was free of ice.