Melting Arctic sea ice may exacerbate future California droughts, researchers say

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Jennifer Xie/Staff

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Melting Arctic sea ice could potentially lead to reduced rainfall in California and exacerbate the possibility and effects of severe drought, a new study found.

With global temperatures rising, the ice in the Arctic Ocean is expected to melt entirely within two or three decades, leading to potential changes in the atmospheric conditions of the northern Pacific Ocean. The study, led by researchers from Lawrence Livermore National Laboratory, found that this loss of sea ice could potentially have adverse effects for winter rainfall in California.

Large-scale warming of the Arctic surface and lower atmosphere affects heat transport from lower latitudes into the Arctic. This in turn results in convection and circulation changes in the tropics,” lead researcher Ivana Cvijanovic said in an email. “Tropical changes lead to the development of a high pressure system over the North Pacific that favors a decrease in rainfall over California.”

The high-pressure ridge in the North Pacific pushes the storms into Alaska and Canada and away from making landfall in California, the study said.

The researchers, including campus geography professor John Chiang, published their findings in the journal Nature Communications on Tuesday.

The group conducted their research using climate simulations in which they compared current control simulations to simulations in which the Arctic has reduced ice during winter months.

The study found that the loss of Arctic sea ice could cause a 10 to 15 percent decrease in California rainfall when considering the 20-year mean, not including the natural variations in rainfall.

“Drought is very much on the mind for Californians because of the long four-year drought that we had recently from roughly 2012 to 2015,” said David Romps, campus associate professor of earth and planetary science and director of the Berkeley Atmospheric Sciences Center.

Romps added that in periods of drought and absence of precipitation, areas are at greater risk for wildfire, referencing recent wildfires in areas such as Napa, Santa Rosa and, most recently, Los Angeles.

These recent wildfires have forced many people to evacuate, and some have caused massive losses in damage to California wineries. The extensive drought in recent years has also caused significant damage to California’s agricultural systems and reduced the number of seasonal jobs in agriculture.

While the study only investigates the impact of reduced sea ice on California rainfall, Chiang said the study suggests that this is only one of various ways that climate change could exacerbate future California droughts.

“The main lesson is that California’s rainfall is susceptible to change, and that we need to understand the causes of such changes, and be prepared for the consequences of such changes,” Chiang said in an email.

Contact Phil Zhang at [email protected] and follow him on Twitter at @philzhangDC.