New analysis highlights importance of groundwater discharge into oceans

An invisible flow of groundwater seeps into the ocean along coastlines all over the world. Scientists have tended to disregard its contributions to ocean chemistry, focusing on the far greater volumes of water and dissolved material entering the sea from rivers and streams, but a study finds that groundwater discharge plays a more significant role than had been thought.

Coastal groundwater discharge can be seen at low tide as rivulets flowing into the ocean. Photo: Jenny Bernier

The findings have implications for global models of biogeochemical cycles and for the interpretation of isotope records of Earth's climate history.

"It's really hard to characterize groundwater discharge, so it has been a source of uncertainty in the modeling of global cycles," said first author Kimberley Mayfield of the University of California, Santa Cruz. "It took a large effort by researchers around the world who came together to make this happen."

The scientists focused on five key elements -- lithium, magnesium, calcium, strontium and barium -- measuring concentrations and isotope ratios in coastal groundwater at 20 sites around the world and using previously published data from additional sites.

"Those elements are important because they come from the weathering of rocks, and weathering of silicate rocks accounts for a huge uptake of carbon dioxide from the atmosphere over long time scales," Mayfield said.

Co-author Adina Paytan of UC Santa Cruz said that groundwater is an important source of inputs to the oceans but has been easy to ignore because it is unseen and hard to measure.

"This is the first global assessment of groundwater discharge for most of these elements," Paytan said. "This information is important for our understanding of how weathering of rock is related to climate, not only in the present but also in the past."

The study estimated that the amount of these elements entering the sea from groundwater is at least 5% and up to 16% of the contributions from rivers, based on the latest global groundwater flux estimates.

"It's important to recognize that groundwater makes a difference globally, and now that we have this large data set, people can keep improving it with more sampling and develop better models of global groundwater discharge," Mayfield said. (National Science Foundation)

YOU MAY ALSO LIKE

New starfish-like fossil reveals evolution in action

Researchers from the University of Cambridge have discovered a fossil of the earliest starfish-like animal, which helps us understand the origins of the nimble-armed creature.

Male butterflies mark their mates with a repulsive smell during sex to ‘turn off’ other suitors

Butterflies have evolved to produce a strongly scented chemical in their genitals, which they leave behind after sex to deter other males from pursuing their mates.

Could we harness energy from black holes?

Study indicates that energy can be extracted from black holes.

The Climate Events of 2020 Show How Excess Heat is Expressed on Earth

By most accounts, 2020 has been a rough year for the planet. It was the warmest year on record, just barely exceeding the record set in 2016 by less than a tenth of a degree according to NASA’s analysis.

Study compares low-fat, plant-based diet to low-carb, animal-based diet

People on a low-fat, plant-based diet ate fewer daily calories but had higher insulin and blood glucose levels, compared to when they ate a low-carbohydrate, animal-based diet.

Organic matter, bacteria doom sea stars to oxygen depletion

Mysterious wasting disease has nearly killed off sea star populations around the world.