Research by Dr Taimoor Sohail and Associate Professor Jan Zika has provided a new framework for understanding freshwater transport and highlights the impact of climate change on the global water cycle.
The global water cycle聽underpins every aspect of human society and our environment, therefore shifting patterns of rain and evaporation have profound consequences for agriculture, infrastructure, and habitats.聽However, quantifying historical water cycle change is challenging, owing to a聽lack of direct observations - particularly over the ocean, where the majority of global precipitation and evaporation occur.
, published today in聽Nature, provides a new estimate of global water cycle change from warm to cold regions while identifying a key inaccuracy in current climate models.聽
The research team, which included John Church and Damien Irving, used ocean salinity as a proxy for rainfall in their study.聽Changes in the ocean鈥檚 salinity can be used as a聽type of rain gauge to detect water cycle changes.聽
A/Prof Zika explains: "When fresh water falls as rain on the ocean, it dilutes the sea water and makes it less salty. When water evaporates from the surface, the salt is retained, increasing the salinity".聽
The team聽developed new methods enabling them to precisely link changes in the ocean鈥檚 salinity to changes in the聽part of the water cycle moving fresh water from warmer to colder regions.聽Their estimates indicate how the broader water cycle is changing in the atmosphere, over land and through聽the oceans.
The team discovered that an additional estimated 46,000 to 77,000 cubic kilometres of water - the equivalent of 123,000 Sydney Harbours worth of freshwater - have shifted聽towards the poles since 1970.聽
This equates聽to 7% more rain in wetter areas, and 7% less rain (or more evaporation) in drier areas, and reveals that between two and four times more freshwater has moved than existing climate models anticipated.
The聽results聽reveal that the聽effects of climate change and rising global temperatures on rainfall are more drastic than previously thought. Long term聽changes to the water cycle are tipped to generate聽more聽intense聽droughts and extreme rainfall events.
The team聽is optimistic聽that the methods聽they are developing will become a mainstay in analysing both observations and climate models.聽
"I would say this is the first time that the poleward transport of freshwater - a critical limb of the water cycle - has ever been quantified", said Dr Sohail. "This finding is going to be particularly useful to scientists and climate modelers who will have a new baseline for freshwater transport that can be used well into the future".聽
