Study of Ocean Salinity Reveals Amped-Up Global Water Cycle

Climate change has boosted the amount of evaporation across Earth’s surface, leading to more frequent extreme weather events from megadroughts to monster hurricanes.

Salinity-contrast time series from 1960 to 2017. (Background photo by Xilin Wang.)

(CN) — There is something in the water on planet Earth.

A study published Wednesday reveals climate change has amplified the water cycle, which explains the more frequent extreme weather patterns in recent years.

The water cycle is the continuous movement of water on Earth. It’s the naturally occurring pattern of rain, runoff, evaporation and repeat, but that cycle is being thrown for a loop as Earth heats up according to the study published in the Journal of Climate.

Saltwater and freshwater have been evaporating at higher rates in the last 50 years while rainfall has increased, according to the study authors.

“The new data demonstrate that the existing salinity pattern has amplified. In other words, ‘the fresh gets fresher, and the salty gets saltier’ in much of the ocean,” study co-author Kevin Trenberth of the National Center for Atmospheric Research said in a statement.

The data points to more freshwater in the Pacific Ocean, broad saltwater levels in the low- and middle-latitudes of the Atlantic and pronounced freshening in North Atlantic, Trenberth said. And there is a noticeable difference between the south and north regions of the Indian Ocean.

“The ocean is where about 93% of the extra heat from global warming ends up and so we find that the ocean every year is warmer than any other. That means it is expanding and sea level is rising,” Trenberth said in an email. “But regional differences also matter.”

Previous theories posited that climate change was affecting the water cycle but available data only went back to the 1960s, according to the study authors.

Lead researcher Lijing Cheng from the Institute of Atmospheric Physics at the Chinese Academy of Science and his team arrived at a simple mathematical solution for their study: they measured the average level of salinity in water samples.

Their findings formed into the Salinity Index (SC) which provides an improved estimate of the planet’s water cycle and how it has changed.

The data shows that the water cycle had been amplified by 2% to 4% per degree of temperature increase since 1960. The United Nations Paris Climate Agreement has set a target goal of capping climate change by 3.6 degrees Fahrenheit.

The study authors forecast that if that cap is reached, then the water cycle could be amplified by 4% to 8%. That increase could be greater if aerosol impacts are smaller in the future than today, according to the study.

Dry regions would become drier, exacerbating droughts, while the risk of extreme rainstorms will increase across the globe — two versions of a worsening climate on the same planet. Crops and livestock, along with worsening wildfires would spread across the United States, China, Australia, Brazil and other countries, which could endanger food safety and human health.

Tropical cyclones and hurricanes would continue to grow and increase damage not only to coastal cities and small island nations, but further inland as well according to the study.

“The ocean regionally can be thought of as a giant rain gauge and thus integrate the otherwise spotty intermittent effects of rainfall,” Trenberth said in his email, noting that rainfall is unevenly distributed across the globe. “The California drought and wildfires relates to this aspect. Other areas suffer flooding.”

Study co-author Nicolas Gruber from Swiss Federal Institute of Technology in Zurich said the data illustrates increases in salinity levels is connected to human influence, because the level of pollution contributed by humans has exceeded the variability or amount of salinity increases that would be naturally found in the environment.

The study was an international collaboration and could provide researchers a better sense of data points for simulations.

The study authors did not immediately respond to an email for questions on the study’s findings.

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