The big freeze: Emerald Bay and its frozen history

SOUTH LAKE TAHOE, Calif. — “The Lake of the Sky” is grabbing attention this winter for more than one reason. Emerald Bay froze completely, including the inlet, for the first time in many years.

“It’s incredible to usher in the first week of spring with a frozen Emerald Bay,” said Laura Patten, senior science policy analyst with the League to Save Lake Tahoe. “The cold temperatures and endless storms we’ve experienced so far this year, juxtaposed with last year’s hot, long and dry summer, demonstrates the extremes the Tahoe Basin faces from climate change.”

David Antonucci, civil/environmental engineer, writer, who lives in Tahoma, told the Tribune, it’s not extremely rare, since it froze over, or mostly froze, before.” 

Antonucci shared some archived newspapers that covered freezes in the past. The Sacramento Daily Union reported March 22, 1880, that the bay had entirely frozen over for the first time since being “settled by the whites.” 

Another set of newspaper clippings provided by Antonucci from the Truckee Republican reported two more times the bay froze in the 1930’s.

Even Santa Cruz Sentinel picked up the phenomena of the bay detailing the experience of a family of five, during which time they were secluded from the rest of the basin by snowfall and freezing temperatures. 

The Sentinel reported the bay froze in 1952 for an unspecified duration Jan. 1 and Feb. 5 and needed supplies were delivered by members of the coast guard auxiliary, “who had to break ice with long poles and shovels for almost a mile before they could dock.”

The coast guard members then allegedly transported 500 pounds of foodstuffs by toboggan to Vikingsholm for the family.  

“I seem to recall it may have frozen over in 1983. It probably wasn’t widely reported because a severe avalanche closed the road for three months that winter,” said Antonucci.

Photographer and part owner of Twilight & Rust Gallery, Jonathan Thompson, also captured a spectacular sunrise over a partially frozen Emerald Bay in 2017. 

Natural Mystic, 2017 Tahoe sunrise over partially frozen bay.
Provided/Jonathan Thompson

“I arrived and was rewarded for the effort with a lovely Sierra sunrise to accompany the spectacular phenomena. Walking back to the truck in daylight, I realized we had snowshoed through a couple fresh avalanche rips on the way in,” Thompson recalled in a post on Facebook. 

Lake Tahoe Facts, a book prepared in cooperation by Antonucci and UC Davis, Tahoe Environmental Research Center, discusses many facts of the lake including the depth and thermodynamics detailing why the lake, in its entirety, doesn’t freeze. 

Emerald Bay at its deepest point is approximately 220 feet with the lake’s maximum depth of 1,645 feet it is the second deepest in the states, and 11th deepest internationally. 

Kaytlen Jackson, State Park Interpreter for California State Parks, told the Tribune a layer of ice, she guessed, about an inch thick was on display the day images were captured that have since gone viral.

“The winds that pushed down the canyon that day were super strong and blew the sheet of ice,” Jackson said and added the photo she saw on Reddit showed it completely frozen over but added it didn’t stay frozen for long.

Emerald Bay frozen for first time in a long while.
Provided/California State Parks

Size isn’t the only reason the big blue lake doesn’t freeze through. 

“Baikal, in the Russian Federation, is the largest lake in the world holding 20% of the world’s unfrozen fresh water,” Antonucci told the Tribune. “The lake freezes every year and it gets thick enough that they can lay railroad tracks and run trains through there.” 

Lake Baikal is the deepest lake in the world and has an annual freeze that lasts from early January until May. 

“Weight per cubic foot equals density, and water is at its most dense at 39 degrees. As the temperature of the water approaches 32 degrees the density decreases causing it to float as ice,” Antonucci said.

“Before a water body can freeze over, the entire water column needs to reach 39 degrees,” said Senior Environmental Scientist, Sierra District, California State Parks, Courtney Rowe, “then, the water can freeze. As water gets cold, it sinks and warmer water replaces it at surface (mixing). This processes repeats until the whole column is cooled (or conditions change). In large bodies of water (Tahoe), the whole column will not get cold enough to allow for freezing.”

Antonucci also said that the recent event, Flipping Out, Lake Tahoe mixes for first time since 2018-19, the lake could have lent a helping hand to this year’s freeze of the bay. 

In addition, water freezes from the perimeter of a lake to the center because the water is shallower at the lake’s edge so it cools off faster, Rowe said and added that the shape (long shorelines, narrow/shallow constriction) along with the relatively shallower depth of Emerald Bay allows for some degree of freezing whereas the main part of Tahoe is too large and too deep to freeze.

Ice forms on Emerald Bay in January.
Provided/BrantAllen/UC Davis TERC

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