An Australian study of ocean salinity over the past 50 years has revealed a "fingerprint" showing that climate change has accelerated the rainfall cycle, a researcher said Friday.

The study published in the journal Science and conducted by Australian and US scientists looked at ocean data from 1950 to 2000 and found that salinity levels had changed in oceans around the world over that time.

Co-author Susan Wijffels said the figures were revealing because ocean salinity was indicative of changes in the water cycle of rainfall and evaporation.

"What the results are saying is we have an ocean fingerprint, a very clear fingerprint, that the earth's water cycle has already spun up," she told AFP.

"What we see in the observations of how the salinity field has changed already over the last 50 years, (is) our hydrological cycle has already intensified significantly."

Wijffels said the pattern was amplifying over time and it could be inferred that the same dynamics were also happening over land.

"What it really means is that the atmosphere can actually shuttle more water from the areas that are drying out to the areas that have lots of rain faster," she said.

"And essentially it means that the wet areas are going to get wetter and the dry areas are going to get drier."

Wijffels said getting a clear picture of what had happened historically with rainfall was frustrating because there was little quality data, and most of this was collected on land, in particular in the northern hemisphere.

"Yet most of the earth's surface is the ocean and actually most of the evaporation that drives our water cycle is happening over the ocean," Wijffels said, making the oceans a worthy object of climate change study.

The researchers from Australian government science and research body CSIRO and the Lawrence Livermore National Laboratory in California used data taken from vessels in oceans around the world and climate models to produce their report.

They revealed a repeating pattern of change believed to be the result of climate change, Wijffels said.

"And we see it in the north Atlantic, the south Atlantic, the north Pacific, the south Pacific, the Indian; it's repeated in every ocean basin independently," she said.

"And the sense of the pattern is that areas that were already fresh have become fresher with lower salinity and areas that were already salty are becoming saltier."