Rare Ice Sheet Forms on a Lake Tahoe Bay

In March, the birds usually begin appearing in Emerald Bay, Calif., as the days get longer and the temperature creeps up, melting the snow that feeds the creeks — the first tantalizing signs of spring. But this month, the bay, on the western shores of Lake Tahoe, has instead been frigid, stark and silent.

In fact, it froze over.

It may be the first time in three decades that the bay has frozen to this extent, according to California State Parks. The last time appears to have been in the early 1990s, said Kaytlen Jackson, who works in communications for the department and who, last week, ventured down the snow-covered slopes to get to the inlet’s edge.

This year has been exceptionally cold in the Lake Tahoe region, and winter storms with heavy snow have shut roads and ski resorts. The bitter temperatures cooled the bay enough to mostly freeze Emerald Bay.

Ms. Jackson, 33, said she had been moved by an image she had seen posted to Reddit that showed ice extending across much of the bay. Though the water, which stretches over about 1,500 acres, often freezes along the shoreline, it is rare for so much of it to freeze.

“I knew that it was a really special thing that was happening,” Ms. Jackson said. “I wanted to take a look at it for myself.”

On March 9, Ms. Jackson and her husband, both avid back country skiers, packed their shovels, probes and beacons and set off down the snow-covered mountain. What she saw was breathtaking: A sheet of ice that nearly covered the entire inlet. “I saw the canyon covered in feet, upon feet, upon feet of snow,” she added. “Like I’ve never seen it before.”

Ms. Jackson, whose job it is to connect visitors with the staggering beauty of California’s landscape, said that standing on the shore, she felt she was brushing up — if ever so briefly — against geological history. Emerald Bay was formed sometime during the Pleistocene Epoch, which lasted from 1.8 million to 11,500 years ago, when glaciers pulverized the surrounding rock, creating a depression. “This thin sheet of ice over the bay is the closest I’m ever going to get to experiencing glaciers like that,” Ms. Jackson said. “It was magical.”

Mitch O’Brien, a 22-year-old ski coach who posted the photograph to Reddit, said that though he had not trekked down to the water, he too had been moved, almost to tears. “I thought I was going to die without seeing that,” Mr. O’Brien said. “I was so blown away.”

The last time Emerald Bay appears to have frozen over was around three decades ago, according to Ms. Jackson’s research and newspaper clippings, which describe the bay having iced over in 1993 and 1989. It is difficult to determine how many times it may have frozen before that, because scientists have only been studying it since the late 1950s, said Geoffrey Schladow, the director of the Tahoe Environmental Research Center at the University of California, Davis.

But, he added, “It’s really unusual.”

For a body of water to freeze over, the entire water column, top to bottom, must reach about 39 degrees. Emerald Bay, which is about 220 feet deep, “reached that magic temperature,” Dr. Schladow said. But Lake Tahoe, which is 1,645 feet at its deepest point, has never frozen over entirely, he added, because of its depth.

Benjamin Carta, whose family runs the Fireside Lodge, about five miles southeast of Emerald Bay, said that most locals were so busy dealing with the relentless storms that they had little time to admire the strange occurrence. “This winter has worn everyone down,” he said. “It’s crazy out here.”

For now, snow has closed the road leading to Emerald Bay. Ms. Jackson, the parks department employee, warned that the ice was definitely not safe to walk, or skate on; she estimated that last week, it was at most a few inches thick in some spots.

She added, “I would guess that it’s melted by now.”

Kitty Bennett contributed research.