Cave secrets unlocked to show past drought and rainfall patterns

July 07, 2019

A first-ever global analysis of cave drip waters has shown where stalagmites can provide vital clues towards understanding past rainfall patterns.

In a study published recently in the prestigious journal Nature Communications, UNSW Sydney scientists led an international group of researchers to amass the data of 163 drip sites in 39 caves on five continents.

They found that in climates that have a mean average temperature of less than 10oC, isotopes of oxygen in cave drip water were similarly composed as those measured in rainwater. As UNSW's Dr Andy Baker explains, this follows what you would expect in colder climates with less evaporation of rainfall.

"This oxygen in the water drips from the stalactites and onto the stalagmites," says Dr Baker, from UNSW's School of Biological and Earth and Environmental Sciences.

"The drip water originally comes from rainfall, providing a direct link to the surface climate. Understanding the extent to which the oxygen isotopic composition of drip water is related to rainfall is a fundamental research question which will unlock the full climate potential of stalagmites and stalactites."

But when the researchers examined the oxygen isotopes in drip waters in warmer areas, the oxygen isotopes in the drip waters corresponded to just some of the rain events, as revealed in the stalagmites. Dr Baker says that in such climates, evaporation not only reduces the amount of rainwater that eventually makes its way to the groundwater (a process known as rainfall recharge), but the oxygen isotopes themselves are changed by this process.

"In hotter climates, recharge to the subsurface doesn't occur from all rain events, rather it likely only occurs after very heavy rain, or seasonally. This study identifies this for the first time and also provides a range of temperatures constraints - this was never known before," he says.

In effect, he says, oxygen isotopes in stalagmites in warmer climates display the balance between wet weather events and prolonged periods of drying.

"For stalagmites in warm regions it suggests that the oxygen isotope composition will tell us about when recharge occurred - in other words, when, and how often," Dr Baker says.

"And that is as valuable as it is unique. In regions like mainland Australia, with extreme weather events like drought and flooding rains, it's a tool to see how often both occurred in the past."

Dr Baker says that with this knowledge it will help us understand how important rainfall is in the replenishment of our groundwater resource.

"This knowledge will improve our understanding of how sustainable our use of groundwater is, especially in regions where groundwater is only recharged by rain," he says.

University of New South Wales

Related Drought Articles from Brightsurf:

Redefining drought in the US corn belt
As the climate trends warmer and drier, global food security increasingly hinges on crops' ability to withstand drought.

The cost of drought in Italy
Drought-induced economic losses ranged in Italy between 0.55 and 1.75 billion euros over the period 2001-2016, and droughts caused significant collateral effects not only on the agricultural sector, but also on food manufacturing industries.

Consequences of the 2018 summer drought
The drought that hit central and northern Europe in summer 2018 had serious effects on crops, forests and grasslands.

Songbirds reduce reproduction to help survive drought
New research from the University of Montana suggests tropical songbirds in both the Old and New Worlds reduce reproduction during severe droughts, and this - somewhat surprisingly -- may actually increase their survival rates.

Predicting drought in the American West just got more difficult
A new, USC-led study of more than 1,000 years of North American droughts and global conditions found that forecasting a lack of precipitation is rarely straightforward.

Where is the water during a drought?
In low precipitation periods - where and how is the limited available water distributed and what possibilities are there for improving retention in the soil and the landscape?

What does drought mean for endangered California salmon?
Droughts threatens California's endangered salmon population -- but pools that serve as drought refuges could make the difference between life and death for these vulnerable fish.

With shrinking snowpack, drought predictability melting away
New research from CU Boulder suggests that during the 21st century, our ability to predict drought using snow will literally melt away.

An evapotranspiration deficit drought index to detect drought impacts on ecosystems
The difference between actual and potential evapotranspiration, technically termed a standardized evapotranspiration deficit drought index (SEDI), can more sensitively capture the biological changes of ecosystems in response to the dynamics of drought intensity, compared with indices based on precipitation and temperature.

Sesame yields stable in drought conditions
Research shows adding sesame to cotton-sorghum crop rotations is possible in west Texas

Read More: Drought News and Drought Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to