Oceans' saltiness reaching extremes

Larry O'Hanlon in Discovery News: The supercharging of Earth's water cycle by global warming is already making some parts of Earth's oceans much saltier while others parts are getting fresher. A new study by Australian scientists shows a clear link between salinity changes at the surface and changes in the deeper waters over the last six decades caused by the warming seen over the same period.

The reasoning goes like this: The saltiness, or salinity, of the oceans is controlled by evaporation and rainfall at Earth's surface, explains Paul Durack of CSIRO, the Australian government's research agency. The more evaporation there is at a given patch of ocean, the more concentrated the salts get in the seawater, and the higher the salinity. In places where lots of rain is falling, the water gets more diluted, becoming fresher.

Tracking salinity changes over the oceans is, then, a great way to monitor the water cycle over the oceans. "A key point is that the general population doesn't live in the oceans, so why should they care about these changes," said Durack who has co-authored with Susan Wijffels a paper in the latest issue of the Journal of Climate.

There are few actual rain gauges in the oceans. Some small island states provide estimates of rainfall over the oceans but largely the rainfall is unmonitored. "So salinity is our proxy for rainfall." In other words, the salinity changes are, in effect, the rain gauges for the oceans…..

"Ocean Waves" by Hokusai (1760-1849)