This file photo shows wild surf breaking on the cliffs of Bronte Beach as a storm continue to lash the coast of Sydney, in 2011. An Australian study of ocean salinity over the past 50 years has revealed a “fingerprint” showing that climate change has accelerated the rainfall cycle, according to a researcher.
An Australian study of ocean salinity over the past 50 years has revealed a “fingerprint” showing that climate change has accelerated the rainfall cycle, according to a researcher.
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.”
More information: Ocean Salinities Reveal Strong Global Water Cycle Intensification During 1950 to 2000, Science 27 April 2012: Vol. 336 no. 6080 pp. 455-458. DOI: 10.1126/science.1212222
Fundamental thermodynamics and climate models suggest that dry regions will become drier and wet regions will become wetter in response to warming. Efforts to detect this long-term response in sparse surface observations of rainfall and evaporation remain ambiguous. We show that ocean salinity patterns express an identifiable fingerprint of an intensifying water cycle. Our 50-year observed global surface salinity changes, combined with changes from global climate models, present robust evidence of an intensified global water cycle at a rate of 8 ± 5% per degree of surface warming. This rate is double the response projected by current-generation climate models and suggests that a substantial (16 to 24%) intensification of the global water cycle will occur in a future 2° to 3° warmer world.
(c) 2012 AFP