A research group from the University of New South Wales has studied changing patterns of salt in the ocean to assess that between 1970 and 2014, at least twice as much freshwater moved from the equator to the poles as our climate models predicted. This gives us visions regarding how the global water cycle is expanding overall.
Climate change draws up our chance of both heavy rains and outrageous droughts. Yet, why - and how - is that? Aren't the two disconnected?
Science has shown that climate change contacts every edge of our planet's ecosystem, and the water cycle is no exception.
Since the cycles included are exceptionally reliant upon temperature, changes in one have resulted in the other.
In particular, as global temperatures have consistently expanded at their fastest rates in millions of years, they have directly impacted water vapor concentrations, clouds, precipitation patterns, and streamflow patterns connected to the water cycle.
So, how does climate change affect the water cycle?
Water evaporates from the land and ocean, returning to Earth as rain and snow.
Climate change intensifies this cycle because more water evaporates up high as air temperatures increase.
Warmer air can hold more water vapor, which can prompt more serious rainstorms, creating major issues like excessive flooding in coastal communities all over the planet.
In any case, it doesn't end there. While certain areas encounter more grounded storms, others encounter more dry air and drought.
As mentioned above, evaporation increases as temperatures rise, drying out soils. When rain falls, much water runs off the hard ground into rivers and streams, leaving the soil dry.
The outcome? Even additional evaporation from the soil and an increased chance of drought.
Increasing temperatures push significantly more freshwater towards the poles than climate models earlier expected.
A UNSW Sydney-led study shows that at least twice as much freshwater has moved from warm to cold areas of the Earth as our climate models predicted, meaning more extensive changes to the global water cycle.
The global water cycle—the consistent movement of freshwater between clouds, land, and the ocean—plays a significant role in our daily routines. This sensitive system transports water from the ocean to the land, making our environment livable and soil fertile.
However, increasing global temperatures have been making this system more extreme: water moves from dry areas to wet regions, making droughts deteriorate in parts of the globe while heightening rainfall circumstances and flooding in others. Wet regions are getting wetter, and dry regions are getting drier.
Changes to the cycle have been challenging recently. Around 80% of worldwide rainfall and evaporation occur directly over the ocean.
Findings show two and four times more freshwater has moved than climate models predicted.
However, another UNSW-led study published in Nature uses changing ocean salt patterns to assess how much freshwater has moved from the equator to the poles since around 1970.
The results show that two to four times more freshwater has moved than climate models predicted, giving us knowledge regarding how the global water cycle is intensifying.
The study's lead author, Dr. Taimoor Sohail, a mathematician and postdoctoral research associate at UNSW Science, stated that they knew from past work that the global water cycle was intensifying. But they didn't know how much.
The movement of freshwater from warm to cold regions forms the largest part of water transport. The researchers' findings illustrate the larger changes occurring in the global water cycle.
The group arrived at their findings by examining observations from three historical data sets covering 1970-2014.
Unexpectedly, instead of direct rainfall, the group focused on how salty the water was in every ocean.
However, rather than focusing on direct rainfall observations—which can be difficult to estimate across the ocean—they focused on a more surprising perspective: the saltiness of the water in every ocean region.
Co-author Jan Zika, an associate professor at the UNSW School of Mathematics and Statistics, states that evaporation eliminates freshwater from the ocean, leaving salt behind in warmer areas and making the ocean saltier. The water cycle then takes that freshwater to colder areas, where it falls as rain, diluting the ocean and leaving it less salty.
Simply put, the water cycle affects the ocean salt pattern, and by estimating these patterns, researchers can trace how the cycle changes over time.
Between 1970 and 2014, an extra 46,000-77,000 cubic kilometers of freshwater were moved from the equator to the poles than predicted.
The team estimated that somewhere in the range of 1970 and 2014, an extra 46,000-77,000 cubic kilometers of freshwater was moved from the equator to the poles than predicted- that is, around 18-30 centimeters of freshwater from tropical and subtropical areas, or around 123,000 times the water in Sydney Harbor.
Changes to the water cycle can affect infrastructure, agriculture, and biodiversity. Thus, it is essential to understand how climate change affects the water cycle now and in the future.
This finding gives us a thought of how much this part of the water cycle is changing and can assist us in further developing future climate change models.
Enhancing Future Predictions
Dr. Sohail and the group compared their discoveries with 20 unique climate models. They found that every model underestimated the change in the warm-cool freshwater move.
Dr. Sohail says the findings could mean they underestimated the effects of climate change on rainfall. Findings like theirs are how they improve on these models.
Every new generation of modeling adjusts past models with real information, tracking down regions they can enhance in later models. This is a natural progression in climate modeling.
Researchers are using the 6th generation of climate modeling (called the Sixth Climate Model Intercomparison Project, or 'CMIP6'), which fused updates from the fifth generation.
This newest finding demonstrates the scientific interaction at work - and could assist with enhancing future predictions.
Clearly describing the change in warm-to-cold freshwater transport implies that they can move ahead and continue making significant predictions about what climate change will probably mean for our global water cycle.
Researchers can use this reference in 10 or 20 years to determine how much these patterns have changed.
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