A group of scientists is searching for environmental hints from millions of years ago to predict what the southwestern climate may look like in the future as temperatures around the world continue to rise due to global warming.
Scientists believed that warmer temperatures may result in heavier and more widespread summer rainfall across the southwest United States by examining ancient climate data.
Using monsoons of the past to predict climate conditions of the future
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Southwest regions of North America have experienced a variety of extreme weather conditions recently, including sweltering heatwaves, scorching wildfires, and monsoon rainstorms that result in flash floods and mudslides, as per ScienceDaily.
A group of scientists from Syracuse University, the University of Connecticut, the University of Arizona, George Mason University, and Harvard University are searching for environmental hints from millions of years ago to predict what the southwestern climate may resemble in the future as a result of global warming.
Scientists further believed that warmer temperatures may result in heavier and more widespread summer rainfall across the southwest United States by examining ancient climate data.
Due to increased aridity from higher temperatures, subtropical regions like southwestern North America are becoming drier as a result of global warming.
However, during the summer, excessive precipitation is occasionally brought on by rising temperatures.
An intensifying monsoon is what's causing this.
Just this past summer, Death Valley and other regions renowned for their lack of rainfall experienced historic flooding as a result of the monsoon's effects in southern California.
Tripti Bhattacharya and Ph.D. candidate in Earth and environmental sciences Claire Rubbelke examined Pliocene-era leaf waxes preserved in ocean sediment cores from Baja California and southern California to learn how the monsoon changed in the middle Pliocene, as per Eurekalert.
These waxes' hydrogen isotopic composition reveals historical changes in the monsoon.
Since rain is the source of the hydrogen required to make leaf waxes, determining the hydrogen concentration can provide information about past precipitation totals.
By passing solvents through sediments at high temperatures and pressures, researchers can extract the waxes from the leaves.
They then separated the waxes by their molecular masses using a device known as a gas chromatograph-isotope ratio mass spectrometer to perform the isotopic measurements.
Driven by changes in temperature
Ran Feng, a professor in the Department of Geosciences at the University of Connecticut and the study's second author, is an expert in climate modeling.
He ran simulations to see how sea surface temperatures might have affected the strength of the North American Monsoon in the mid-Pliocene.
Her team discovered that the Pacific's ocean temperatures were set up in such a way as to move more moisture from the tropics to the subtropics.
Particularly, the gradient of temperature between the subtropics and the tropics, which is what drives the strengthening of the North American monsoon, was lessened.
One of the key determinants of monsoon intensity is temperature.
Rainfall favorability is decreased as a result of descending motion over many monsoon regions in southwestern North America due to warmer conditions in the eastern equatorial Pacific.
However, when the California margin is warmer than the eastern equatorial Pacific, as it can be during current marine heat wave events, more tropical moisture enters the subtropics, bringing more precipitation from the North American monsoon.
