Climate records from the Antarctic ice cores are only about a million years old and need a climate that can support ice to be valid. Some 15 to 17 million years ago, a warmer Spain was glimpsed by using leaf wax. Southwest Africa has had a 3.5 million-year history of precipitation.
While working in the lab, Bhattacharya began to use them. She and a colleague came up with the idea of studying the Pliocene while riding a bus.
The Joides Resolution is a research vessel that travels the oceans drilling core from as deep as 6 miles below the surface. One of the samples used for the study was taken off the coast of California from a depth of more than 2,600 meters, while the other was taken off the east coast of Mexico. The leaf waxes would have been transported west on the wind.
The team got a cube of each core, freeze dried them, and used a solvent under pressure to extract the waxes. They separated the waxes by their mass using a gas chromatograph-isotope ratio mass spectrometer.
The hydrogen that is used to make the wax comes from the water that the plant uses. You can see that it's like a fingerprints. The kind of rain you have is traced by the isotopes. They can compare the amount of winter and summer rain. It is quite powerful.
In the second part of the study, a professor at the University of Connecticut ran simulations to find out how sea temperatures affect monsoons. When the marine temperatures in the area from Alaska to off the coast of Baja, California were higher than the tropical waters off Central America, there was a chance for stronger monsoons in the Southwest. The relatively cooler tropical air is pulled in by the warmer local air. She explains that it creates a loop. The Southwest North America regions can be driven into by this.
As temperatures rise, more intense monsoon storms will be fed by a marine heat wave off California.
There will be monsoons that will help with the Southwest's dry spell. They will be stronger and will cause more flooding. In Arizona, the monsoon accounts for 60 percent of the precipitation. In the desert, it is an important source of water. It replenishes the water in some systems. The flip side of that is that monsoon storms can be so intense and so quick that a lot of the water can end up off the landscape. It's not always the case that it replenishes the water table.
As the climate has changed, design standards for infrastructure have not kept pace. The Atlas 14 reports for the US Southwest do not rely on a changing future but on historical amounts. The Southwest study was updated in 2011.
There is a connection between monsoons and fires. The growth of fuel loads is increased by the growth of plants. Bigger fires were set off by the subsequent droughts.
She says that a stronger monsoon season creates unforeseen dangers from fire and flooding. We are going to look at how fire and flooding respond to a warmer climate.