(Wines&Vines) - As temperatures plunged late on the night of Nov. 25, the pickers prepared to move in and pluck frozen grapes from their frosty vines on the slopes above Okanagan Lake.

But fewer wineries than usual registered intentions to produce ice wine this year, and fewer acres are slated to be harvested for the golden liquid that constitutes a sweet slice of Canadiana for consumers across Asia.

According to the B.C. Wine Authority, just 20 wineries designated 169 acres for ice wine this year, for a potential harvest of 722 tons. That’s the least since 2010, when 24 wines registered their intention to harvest 520 tons.

The shift comes despite some of the earliest ice wine harvests on record: In 2014, grapes were picked Nov. 12, the second-earliest harvest ever, while the harvest Jan. 1, 2013, is the only occasion since 2010 that grapes weren’t picked in November.

While some of the hottest, driest years on record have focussed attention on climate change, ice wine seems unscathed.

So why did producers step away this year, and why have long-time producers such as Hainle Vineyards—which made Canada’s first commercially produced ice wine in 1978—chosen to pull out their vines?
The answer is two-fold, and as much the result of shifting tastes as shifting weather patterns.
Part of the gamble of ice wine production is actually getting a cold snap sufficient to meet production requirements. By law, ice wine must be made from grapes frozen on the vine at temperatures of -8? C (17.6? F), or lower and the pressed grape juice must be a minimum of 35? Brix.

This isn’t necessarily a challenge in cool climates, but warmer winters in recent decades have meant an overall reduction in opportunities to achieve those requirements, said Greg Jones of Southern Oregon University.

Jones’ most recent weather update to growers noted that average temperatures year-to-date continue to run 1? to 4? F or more above the 30-year normal, with winter conditions in the Northwest also proving to be warmer than usual. “Globally 2015 is on track to be the warmest year since good records have been kept,” he said.

Desication of grapes as the winter progresses, which can concentrate flavours, not to mention losses to birds and other critters, also means less tonnage—as much as 25% less for each month the grapes are left. Many winemakers, also mindful of scheduling, are keen to harvest the grapes they’ve designated for ice wine as soon as possible to ensure they’ve got the most juice possible.
“Usually I jump at the first opportunity to pull off the fruit for ice wine because you just don’t know,” Derek Kontkanen, winemaker at Jackson-Triggs Okanagan, told Wines & Vines. “Last year we left quite a bit on the vine for ice wine, and the harvest came very early, Nov. 12, so we didn’t actually lose any of the grapes we thought we were going to lose.”

The result was effectively a bumper crop of grapes that kept Jackson-Triggs’ cellar stocked. Since ice wine is a significant capital investment for wineries, most take pains to tailor production to demand to ensure cash flow. With more ice wine than expected from last year’s vintage, reserving grapes for the harvest this year wasn’t necessary.

“By next year, we’ll be harvesting ice wine again,” Kontkanen said.

Shifting tastes have also factored into production decisions, however.

The Huber family, the current owners of Hainle Vineyards, announced plans to replant the vineyard that provided grapes for Canada’s first commercial ice wine to Pinot Noir earlier this year, a move contemplated since wildfires scorched the property in 2012.