While ocean lovers might beg to differ, lakes can make a big impression. After all, the largest are known to significantly affect local weather patterns. Researchers have now used a hydrological model to investigate how changes in the surface area of Utah’s Great Salt Lake—a body of water that has shrunk substantially in recent decades—might alter precipitation near the lake. The team found that a 25% decrease in the lake’s area translated into a roughly 10% decrease in total precipitation during a case study storm event.
Given that the Great Salt Lake has already shrunk to less than a third of the size it was in 1980, these findings highlight how precipitation—and ultimately water availability—could substantially change in the region in the future, the researchers concluded.
Have Lake, Will Change Weather
Today the Great Salt Lake covers roughly 2,500 square kilometers (970 square miles)—that’s more than 40 times the area of Manhattan. But that footprint size pales in comparison with that of the lake’s predecessor: 18,000 or so years ago, prehistoric Lake Bonneville rivaled Lake Superior in size (1,400 Manhattans). Even so, the current Great Salt Lake is large enough to influence local weather patterns.
Air can pick up moisture and heat from the lake’s surface, explained Hongping Gu, an atmospheric scientist at Utah State University in Logan. “These processes can lead to increased precipitation over and downwind of the lake.”
That so-called lake effect has been documented for many large lakes. Gu and her colleagues were keen to understand how the magnitude of the lake effect of the Great Salt Lake might vary in the future.
The Great Salt Lake has been shrinking in recent decades, and it makes sense that such a change might also shift precipitation patterns in the area, said Gu. “Our goal was to understand how different levels of lake reduction will impact local precipitation.”
The researchers coupled a regional climate model with a model of the Great Salt Lake. The team opted to focus on one storm that occurred near the Great Salt Lake in June 2017. That event set precipitation records, said Wei Zhang, a climate scientist at Utah State University and a member of the research team. “We selected that case because it had very heavy precipitation.” Over the course of several days, the storm dumped more than 180 millimeters (7 inches) of precipitation.
Imagining a Smaller Lake
Gu and her collaborators modeled how precipitation associated with that summer storm would have varied if the Great Salt Lake had been smaller. The team considered five different lake areas: 100%, 75%, 50%, 25%, and 0% of the lake extent measured in 2004. In each case in their model, the researchers replaced cells containing lake water with cells containing locally representative vegetation.
The team found a clear correlation between lake area and precipitation: As the lake shrank, the amount of precipitation that fell downwind of the lake decreased. Reducing the lake’s area by 25% resulted in a roughly 10% decrease in total storm precipitation; removing the lake entirely halved precipitation within a few tens of kilometers of the lake, the researchers noted.
“It’s a very robust signal.”
Though these results are based on just one storm event, they’re striking nonetheless, said Zhang. “It’s a very robust signal.”
And if other storms follow the same pattern, that could spell bad news for the already shrinking Great Salt Lake, he continued. That’s because the lake is fed by runoff from snowpack, which is in turn nourished by local precipitation. As the Great Salt Lake gets smaller, there might be less and less runoff to replenish it, said Zhang. “It’s active feedback.”
The results were published in the Journal of Hydrometeorology in June.
An Eye Toward Winter and Dust
But it’s also important not to overextrapolate the findings from just one event, said Jim Steenburgh, an atmospheric scientist at the University of Utah in Salt Lake City, not involved in the research. After all, not all storms that strike near the Great Salt Lake are affected by the lake’s presence, he said. So-called lake effect wintertime precipitation likely accounts for less than 10% of all wintertime precipitation, Steenburgh has estimated.
It’s also unknown whether winter storms would exhibit the same shifts in precipitation that summer storms do, he said. Winter storms are the ones building snowpack in the region, so it’s particularly important to study those events. “I’d like to see impacts on winter storms,” said Steenburgh.
“It’s a collector of all kinds of stuff.”
Besides modeling other storms in the future, Gu and her colleagues are also looking to incorporate the effects of aerosols and air pollution into their simulations. Like California’s Salton Sea, the dry lake bed of the Great Salt Lake is a source of dust. And there’s also often chemicals entrained in that dust.
Residues from agricultural runoff, for instance, make their way into the lake, said Steenburgh. “It’s a collector of all kinds of stuff.” All that material, some of which is harmful to human health, can become resuspended in the atmosphere as the lake bed dries up, he said.
There are efforts underway to preserve the Great Salt Lake. In 2022, the governor of Utah suspended new appropriations of water in the Great Salt Lake Basin. Water conservation bills have frequently appeared before the Utah legislature in recent years, and numerous grassroots organizations like Save Our Great Salt Lake have sprung up.
—Katherine Kornei (@KatherineKornei), Science Writer
Discussion about this post