As Southcentral Alaska temperatures rise once again this week, will early-season ice skaters who've been carving turns on marvelous snow-free ice be forced to shore?
Skaters have been out in force on area lakes the last two weeks. Skating tracks on Goose Lake, Westchester Lagoon, Potter Marsh are common, with more adventurous skaters taking to lakes in the Mat-Su or Kenai Peninsula.
Ice-covered lakes are not unusual this time of year. What is unusual is the lack of snow on top of the ice, leaving backcountry skaters such as Anchorage's Kevin Turinsky a little gaga.
"Yesterday, we went to Nancy Lake," Turinsky said Monday night, "and the conditions were just sublime. Absolutely spectacular. The ice is just unbelievably great. In fact, it's hard enough I'll have to sharpen my skates tomorrow. It's very, very smooth -- no pressure ridges. Just fantastic.
"Everybody is complaining about the lack of snow, but I'm loving it. Last year I barely got any skating done."
That's unusual for Turinsky, 50, an avid skater who did a 40-kilometer trek across Kenai Lake in ideal conditions a few years ago. He uses long-bladed touring or nordic skates, travels with friends and carries an array of safety equipment including a throw bag, ice claws, fire starter, and some extra dry clothes. "If it goes bad," Turinsky said, "it's going to go really bad.
"Ice is never consistent. You might be trucking along and have no idea there's a natural spring or a methane leak in a particular area. Sometimes streams flowing into a lake are hard to identify."
That said, Turkinsky has skated for years and never fallen through the ice. He noted three spots with open water on Nancy Lake last weekend "and they're predictable – where a stream might come in, for instance.
"But if you were going fast and it was dark at night and you weren't paying attention, you might run into it."
Selling skates, not skis
With such prime skating conditions and no snow for skiing, Alaska Mountaineering and Hiking owner Paul Denkewalter said he's sold out of ice skates, including Lundhag and Isvidda nordic skates that clip onto ski boots and feature long blades up the 55 centimeters long. "But it's killing me because we don't sell as many skates as we do skis. Stupid weather."
AMH offers rentals too, as do other stores with outdoor gear.
Long blades allow skaters to maintain speed without as many strides. "They don't have a cavity in the blade, so they're really stable and fast," Denkewalter said. "It's like a sea kayak vs. a river kayak. They're quite stable."
Added Turinsky: "You put these touring skates on, and it's a really long glide. So you're not wearing yourself out. It's low impact."
Awaiting hot mopping
Far more skaters will stick to familiar waterways, and for them, the Municipality of Anchorage maintains outdoor skating rinks at several lakes around town, including Westchester Lagoon, Cheney Lake, and the Cuddy Family Midtown Park. However, those lakes only open for skating when ice thickness reaches a depth of 12 inches or greater according to the Municipality's Parks and Recreation Department webpage. The lakes must be able to support the weight of a truck with a plow attachment and a full water tank used for hot mopping the surface -- about 7,000 pounds -- before they are formally opened to the public. Typically this occurs around the first week of December.
Who determined that 12 inches is sufficient for supporting 7,000 pounds?
The short answer is through trial, error and research. The Canadian government pioneered research into the construction and maintenance of ice roads. When driving trucks on ice roads, any vehicle that fell through was easily identified as being too heavy. After enough vehicles fell through, a set of minimum guidelines were developed.
In addition, the physical structure of ice is easily tested in a laboratory setting to determine its so-called strength coefficients. The results of these tests allow scientists to determine how much weight ice of any thickness can support. The formulas say that a 200-pound person is minimally supported by about 1 1/2 inches of good ice. The key terms are "minimally" and "good ice." If the 200-pounder takes enough steps on 1 1/2 inch ice, eventually he or she will reach a weak spot and break through.
Clearly, a higher safety threshhold is needed.
"Good ice" describes ice:
• With few air bubbles;
• That hasn't endured repeated freeze-thaw cycles; and
• That is smooth, not slushy, without standing water.
6.5 inches ice
Most public safety agencies in the U.S. and Canada use a conservative safety factor for their recreation guidelines, which indicates that 2 inches of ice will support about 200 pounds, 4 inches will support about 800 pounds, 6 inches will support about 1,800 pounds, and 8 inches will support about 3,200 pounds. These are considered maximum safety values for "good ice."
Most lakes around Anchorage are reporting ice 6.5 to 7.5 inches of ice this week, more than enough to support groups of ice skaters assuming that areas of thin ice aren't mixed in.
Potter Marsh, the 564-acre coastal marsh at the southern end of the Anchorage Coastal Wildlife Refuge, can be problematic because the freeze rate is different in shallow water versus deep water and also different where grasses, sedges, and cattails rise above the surface.
Another warm up
Unfortunately for area skaters, above-freezing temperatures returned to Anchorage. According to the 10-day Anchorage weather forecast, the high will reach or exceed freezing six days. This will cause slight surface melting on some lakes. As long as several hours of below freezing temperatures are observed each night, though, the ice should not thin much, if at all.
Still, it's important to carry safety gear and skate with one or more companions. In addition to a throw bag, ice claws, fire starter, and some extra dry clothes, skaters might consider an inflatable life vest.
In a typical winter warm up, snow melt drains directly into lakes, which deteriorates near-shore ice and hastens the overall lake ice degradation. But this winter, only 1 inch of snow was on the ground at freeze-up and that has since vanished.
Through Tuesday, there have been 19 skating days this fall and early winter. This far exceeds the long-term average of 8.5 skating days before an inch of snow covers the ice, according to weather statistics. Many years, in fact, see no skating days. However, 1923 saw a whopping 51 days with ice thick enough to skate on beneath less than an inch of snow. How many more days of unrestricted skating are left this year? Only time will tell.
Brian Brettschneider is an Anchorage-based environmental planner and climatologist who writes an Alaska weather blog. Mike Campbell of Alaska Dispatch News contributed.