Ice Jam Floods

When do you expect flooding?

It depends very much on where you are, of course, and what causes the flooding. Here in interior Alaska we have two flood seasons, with two quite different mechanisms, and we’re starting into one of them now, at the driest time of the year.

Yes, April is our driest month and May, while a little wetter, is the second driest month with temperatures above freezing. So why flooding now? Why not in the rainiest month, August, which did produce the great Fairbanks Flood of 1967?

Two words: ice jams.

We’re already getting some information on river breakup and flood warnings. In fact, there is an ice jam flood advisory on the Tanana River near the mouth of the Salcha (upstream of Fairbanks) today and tomorrow. Most of the rivers in Alaska run from highlands with snow — lots of snow — in the winter months to coasts that during the spring are a lot colder than the interior where the snow is melting under the sun. The snow melts and the meltwater runs into the river while the lower reaches of the river are still frozen. As the river rises and the sun weakens the ice that has covered it over the winter, the ice breaks into chunks and slabs and begins to flow with the river. It used to be axiomatic that rivers could not be crossed, and bridges were often swept away, during breakup, when the ice is carried downriver. When I came to Fairbanks it was still a possibility that the last car of the year over the ice bridge across the Chena River would go through the ice. The great gambling event of the Alaskan Spring is the Nenana Ice Pool – wagering on the exact day, hour, and minute that the ice will go out at Nenana, Alaska.

But all that ice moving downriver can cause problems, too. It’s not wimpy, thin ice; the ice at Nenana is over 2’ thick today, and while it’s thinned from is original 3 ½ feet, it still makes big chunks. If it piles up, as may happen at a different place every year, the flow of water is severely impeded, and the water spreads out over the adjacent land. Rivers in Alaska are transportation corridors – not only for boats in the summer, but for dog teams and snow machines in the winter. Consequently most of the older settlements in Alaska are on this precursor to our skimpy road net, and they almost expect to be flooded in spring. Fuel lines and tanks must be tied down, as must boardwalks, lest they float off. Belongings are put up high. I expect the public service announcements warning residents to prepare for flooding to start soon.

By the way, notice that our wettest month has an average precipitation of under 2″, and the annual total is only 10.31″. In terms of total precipitation, I live in a desert.

North Pole Weather, 4/16/12

Sunrise this morning was 6:10 pm, with sunset not until 9:33 this afternoon for 15 hours 23 minutes of daylight. We’re still gaining almost 7 minutes a day, but the snow, while pretty wet lately, is far from gone. The snow stake shows just under a foot still on the ground. There’s been enough melting that the path to the shed (and the tricycle) is impossible to shovel – it’s ice. Too bad, as they’ve plowed the bicycle path, though the tenth of a mile of dirt road to get to it is a horrible mixture of mud, ice, and potholes. But the edges of the raised beds are poking out of the snow, and at this rate I’ll be able to see the soil in the beds beds themselves pretty soon. It was actually above freezing this morning at 7 am.

I’ve started wearing my athletic shoes when I go anywhere, just tossing the boots in the car in case I encounter ice. I’m actually getting to attend evening functions, like The Stoned Guest (P.D.Q. Bach) Friday night. I need to start the beans next week, and the squash the week after that. Time to start visiting the greenhouses, too – I rely on them for culinary herb plants and flowers.

If only I weren’t so busy with OLLI classes this month! Northern vegetation changes and archaeological science Monday, iPhoto and digital photography Wednesday, astrophysics Friday, and a weekend workshop on fiction writing at the beginning of next month. Hope I can remember to keep the plants watered!

p.s. at 4 pm: temperature +57°F and I had to take off my jacket and turn on the air conditioning driving home! Still plenty of snow, though — the snow stake says 8″, though lots of bare ground, as well as mud and puddles,  are showing.

Breakup Season

The usual four seasons, especially as defined by the equinoxes and solstices, don’t work very well for interior Alaska. Show cover is generally established by a month after the autumnal equinox, and stays on the ground until well after the vernal equinox. Rivers freeze a little later and remain frozen longer in the spring, and the only running water for six months of the year is in hot springs and indoors. But there is one season that everyone both longs for and dreads: Breakup.

Breakup is the time of year when snow melts and rivers thaw. The two are connected by more than sunshine and warmer weather. Melting snow makes mud (one of the reasons breakup is a time of some dread) but it also runs into rivers. If the water rises in the upper stretches of a river before lower reaches are thawed, as often happens in Alaska, the result can be ice jams and resultant flooding. I’ll talk about that some other time, but right now I want to discuss the simple process of melting snow.

Clean snow reflects most of the solar energy that strikes it. Some of the sun’s rays are absorbed within the snow pack, and cause internal melting and settling — but this is a slow process. Even clean snow, however, is a very good absorber in thermal infrared wavelengths. The sun doesn’t put out much energy in these wavelengths, but buildings, trees, and just about everything else except polished metal does. As a result, snow near the south side of a building melts much faster than snow out in the open. So does snow near tree trunks.

I see this every year. In addition to the photo of my road, which is rapidly turning into mud, I took two of the north and south yards of my house, minutes apart. Both areas got almost exactly the same amount of snow, and both have very similar exposure to sunlight. The snow stake still has a good 18” of snow. The ground around the birch is almost bare.

Why? Two reasons, actually, and the combination explains why open birch forest is usually the first natural area free of snow around here. First, birch trees hold their seeds through winter, and drop them shortly before breakup. As a result the seeds on the snow around the tree absorb the solar radiation and transfer that energy to the snow, speeding its melt. Natural selection? Quite possibly. It certainly seems likely that the enhanced snow melt, leading to earlier warming of the ground, would help the tree.

Second, the tree itself absorbs some solar energy, and then re-radiates it to the snow in the form of thermal infrared. Just about any object poking through the snow this time of year has a little depression around it. Spruce trees do an even better job of absorbing sunlight than do birches, but they also shade the ground and transfer much of the energy they absorb directly to the air. As a result spruce forest, while it probably does a better job of warming the air than birch forest, is among the last areas to have completely bare ground.

On a different note entirely, one of the fixtures of breakup in Fairbanks is the Beat Beethoven 5 km race, a fundraiser held today for and by the Fairbanks Symphony Orchestra. I won’t be running this year, though I did “run” with a cane once — and came in last. The idea is to cover the 5 km before the end of Beethoven’s 5th Symphony, about 30 minutes. I’m volunteering this year to park my car along the race route with the radio tuned to 91.5 (KSUA, the campus radio station) blaring out Beethoven’s 5th. I expect temperatures below 50°F and much of the course to be slippery or wet!

Added later (after the race.) This is definitely a family race. There were parents pushing their children in strollers, parents with children in backpacks or riding piggyback, dogs, and one contestant on crutches. (And she wasn’t at the end, either.) I did have a bit of a problem in that instruction to volunteers said if possible, not to have your car idling as the runner went by. I did. And needed a jump to start the car after the battery totally discharged itself.

North Pole Weather 3/19/12 and #WriteMotivation

No, that's not Alaska! My sister took this photo this past weekend in California. I couldn't resist sharing the snow-covered palms.

The sun rose (past tense!) this morning at 7:53 and will set this evening at 8:06, for 12 hr 13 min of daylight. What, you say, more than 12 hours when the equinox isn’t until tomorrow? The combination of atmospheric refraction and the finite diameter of the sun always ensures that the day is a little longer than geometry would have it, and as far as I’m concerned, it’s spring!

Not in temperature. That’s been above zero most days and below zero most nights, and there’s been virtually no melting of the snow so far. It has, however, settled. A week ago we had close to 2 ½’ on the ground; today it’s just a little over 2’. The sun, when it’s out, is high enough that a fair amount of energy is absorbed within the snowpack, and the bonds between crystals are slowly collapsing. I don’t think we’re losing any mass yet, though, except by evaporation. We can get 40 below this late,  so I’m not complaining about temperatures in the teens.

Besides, look what my sister ran into day before yesterday in California!

It’s light long enough in the evening now I can get out and do things. Yesterday afternoon I attended a matinee performance of The Music Man put on by FLOT, and was actually able to drive home in daylight afterwards.

#WriteMotivation:

One thing that wasn’t on the list: I made transfers from my book cover, with the award sticker, and applied them to a tote bag and T-shirt. I also revamped my bookmarks.

1. Learn to use at least one legal method of getting images other than photos I’ve taken on my blog. DONE, though I’m still looking for an African brush fire for next week.

2. Continue to blog at least 5 days a week. (I’m doing 7 now, but I’ve signed up for a number of adult classes in March.)  On Track. I’ve posted every day so far this month, and I have 7 written and scheduled for the 12 days remaining. The other 5 are still in the idea stage, but I do have ideas. And I’ve made my OLLI classes so far, even the day I managed to high-center the car in a whiteout and had to get it pulled out by a tow truck.

3. Edit Chs 2 and 9 of my WIP to give more showing, less telling. (Ch 2 has been on Six Sentence Sunday; Ch 9 is the next section from Tod’s POV.)  I haven’t even looked at Chapter 9 yet.

4. Participate in at least one Platform-building challenge. I did both.