Lake in Eastern Sierra Nevada Mountains could explain California’s drought

Lake in Eastern Sierra Nevada Mountains could explain California’s drought

A mountain lake in California may provide answers surrounding the current five year drought as well as the other major droughts in the history of the state.

Glen MacDonald, a climate change researcher and professor at the University of California, Los Angeles led a study in which he has analyzed the relationship between prolonged drought, surface sea temperatures, and the previous periods indicating climate warming.

The research team chose a lake in the Eastern Sierra Nevada Mountains and analyzed the organic matter collected from the sediments of the lake in an effort to find out the changing patterns in its past climate and water conditions. They then linked and compared the data collected with the data from Pacific Ocean marine sediment.

Through the study, the researchers have found a relationship between the periods of drought that occurred in the American West between 5,000 and 1,000 BC and also during the European Middle Ages, with the warming of the climate and cool temperatures of the eastern Pacific Ocean. They attributed the relationship to a La Niña-like event which implies that cool ocean temperatures intensify the effects of climate change.

It is not clear yet whether the climate change caused by human activity would affect the Pacific Ocean and consequently the Californian drought.

But there is a possibility that California's current drought is only the beginning of a longer shift, the researchers say. If California does settle into an extended period of aridity, MacDonald has some ideas about what to expect, based on previous climate conditions.

The researchers fear that the current drought situation in California is just the beginning of a longer trend. Dr. MacDonald said in a press release, “We would expect temperatures to get higher, and rainfall and snowfall would decrease. Fire activity could increase, and lakes would get shallower, with some becoming marshy or drying up”.

The study paper published in the scientific journal UCLA News informed...

“Radiative forcing in the past appears to have had catastrophic effects in extending droughts,” said MacDonald, an international authority on drought and climate change. “When you have arid periods that persist for 60 years, as we did in the 12th century, or for millennia, as we did from 6,000 to 1,000 B.C., that’s not really a ‘drought.’ That aridity is the new normal.”

Researchers tracked California’s historic and prehistoric climate and water conditions by taking a sediment core in the Sierra Nevada mountains. They pulled a 2-inch-wide, 10-foot-deep cylinder of sediment from the bottom of Kirman Lake and analyzed it in third-of-an­-inch sections, creating the most detailed and continuous paleoenvironmental record of California.

“Climate models today have a challenging time predicting what will happen with Pacific sea-surface temperatures in the face of climate change, and we hope that our research can improve that.”

The team found evidence though that through the millennia Kirman Lake has grown more and less salty, dried until it was exclusively marshland and refilled again. All the while, sediment accumulated on the lake’s bottom, forming a record of lake conditions, the changing climate and the surrounding environment.

The research team spent years analyzing the core sample, which revealed California’s history layer by layer:

charcoal deposits indicate when wildfires were more prevalent.
layers of fossilized pollen shows eras of more pine trees or drier sagebrush.
shells from mollusks indicate times of deeper water.
single-celled algae and molecules of carbon and nitrogen give clues to the lake’s depth and salinity, and the abundance or waning of plant and animal life.

“We suspected we would see the millennia of aridity during the mid-Holocene at Kirman Lake, but we were surprised to see a very clear record of the medieval climate anomaly as well,” MacDonald said. “It was very cool to see the lake was sensitive on the scale of not just thousands of years, but also something that lasted just a few centuries.”



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