California Drought Report #73: The Pacific Ocean Surface Temperatures Controls CA Drought Potential

Prolonged California aridity linked to climate warming and Pacific sea surface temperature, Nature Scientific Reports.

This was just another Greenhouse Gas scare report, claiming that greenhouse gasses could be the future driver of CA droughts. Ignoring the references to scary climate change the study has some interesting findings on historic drought conditions.

 

The research team spent years analyzing the core sample drawn from Kirman Lake in the Central Sierra, which revealed California’s climate history layer by layer for 10,000 years.

  • 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.

From 6,000 to 1,000 B.C., during a time geologists refer to as the mid-Holocene, the core sample captures a 5,000-year dry period in California that has been seen in less detail through other paleoenvironmental records. This arid period is linked to a slight variation in Earth’s orbit that increased the amount of solar energy received by the Northern Hemisphere in the summer months. California was warm and dry, while marine sediment records show the Pacific was in a La Niña-like state, likely reducing precipitation.

A similar dry period was seen from about 950 to 1250 B.C.[D.C.], a time known as the medieval climate anomaly. Increased radiative forcing and warming at this time is connected to decreased volcanic activity and increased sunspots. Again, La Niña appears to have reigned in the Pacific Ocean.

“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.”

Even more exciting to the researchers was a brief shift in the record toward moister conditions around 2,200 B.C. In the middle of thousands of years of mid-Holocene dryness, Kirman Lake suddenly became moister again, MacDonald said, while simultaneously the Pacific Ocean record switched to more El Niño-like conditions.

“This change at 2,200 B.C. was a global phenomenon,” MacDonald said. “It’s associated with the collapse of the Old Kingdom in Egypt. It’s linked to the decline of the Akkadian Empire in Mesopotamia and similar Bronze Age societal disruptions in India and China. It was amazing to find evidence of it in our own backyard.”

That blip in the record was a reminder that El Niño and La Niña weather patterns have global repercussions. It also confirmed the accuracy and sensitivity of Kirman Lake’s record and the strong link between the ocean and California’s weather.

See the highlighted text. La Niña weather patterns bring more drought conditions,some lasting long periods, much longer than the five to six years of drought we have experienced in the last 100 years. We are on the cusp of a La Niña condition in the Pacific. Stay Tuned.

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About Russ Steele

Freelance writer and climate change blogger. Russ spent twenty years in the Air Force as a navigator specializing in electronics warfare and digital systems. After his service he was employed for sixteen years as concept developer for TRW, an aerospace and automotive company, and then was CEO of a non-profit Internet provider for 18 months. Russ's articles have appeared in Comstock's Business, Capitol Journal, Trailer Life, Monitoring Times, and Idaho Magazine.
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