From Vanderbilt University and the “yes, but if it happened today, it would be blamed on global warming” department.
Wet and stormy weather lashed California coast… 8,200 years ago
First high resolution evidence of California climate response to Holocene 8.2 ka event
The weather report for California 8,200 years ago was exceptionally wet and stormy.
That is the conclusion of a paleoclimate study that analyzed stalagmite records from White Moon Cave in the Santa Cruz Mountains published online Jun. 20 in Scientific Reports.
The Golden State’s 150-year stretch of unusually wet weather appears to have been marked by particularly intense winter storms and coincides with a climate anomaly in Greenland ice cores first detected in 1997. Before this “8.2 ka event” was discovered scientists thought the world’s climate had been unusually stable during the Holocene, the geological epoch that covers the last 11,700 years of Earth’s history.
Since then researchers have associated the distinctive, 3.3-degree Celsius temperature dip in the Greenland ice cores with a catastrophic event: The drainage of two giant glacial lakes (Lake Ojibway and Lake Agassiz) located in northeastern North America caused by the collapse of massive ice sheet that covered much of the continent during the last ice age. In short order, the two lakes dumped enough melt water into the North Atlantic to disrupt the world’s oceanic and atmospheric circulation patterns and raise the sea level by somewhere between two to 10 feet. The tremendous freshwater flood has been associated with an extended cold snap in Europe, increased drought in Africa, weakened monsoons in Asia and strengthened monsoons in South America.
“This is the first high-resolution evidence of the response of the coastal California climate to the most distinctive event in the Holocene. Although the effects appear to have been less severe than in other parts of the world, it provides us with new information about the nature of this global climate event,” said Jessica Oster, assistant professor of earth and environmental sciences at Vanderbilt University, who directed the study.
Oster is a member of a small community of earth scientists pioneering the use of mineral deposits in caves as proxies for the prehistoric climate. Cave formations, including stalagmites and stalactites, can provide valuable information about the climate for the last 600,000 years. They have a built-in clock: The mineral deposits contain radioactive uranium-234 that decays into thorium-230 at a constant rate so the ratio of the two isotopes is determined by the date the mineral deposit formed. Seasonal variations in water seepage produce layers that can be dated with considerable precision. The ratios of other isotopes in the minerals including oxygen and carbon provide information about the temperature and nature of the vegetation in the region at the time the layers formed. Concentrations of trace elements like magnesium, strontium and phosphorus provide information about how wet the environment was.
“Events like this are particularly difficult to study because they are so brief,” said Oster. “Fast-growing stalagmites are particularly good for this purpose because they have very high temporal resolution.”