The team from Hefei University of Technology in China has made a groundbreaking connection between the amount of silver buried in marine sediments and anthropogenic climate change. According to the researchers, global warming is leading to the burial of vast silver reserves on the floor of the South China Sea, and similar processes may be occurring throughout the world’s oceans. The quantity of silver hidden beneath the sea off the coast of Vietnam has surged since 1850, the study’s authors reported. This coincides with the onset of the Industrial Revolution, when humans began releasing greenhouse gases into the atmosphere on a large scale, as noted by Live Science.
This is the first study to uncover a potential link between silver cycles in the ocean and global warming, said lead author Lichuan Xu, an assistant professor in Earth Sciences. The findings suggest that global warming could have unknown consequences for other trace elements as well, the scientist added.
So, how does silver concentrate and behave underwater? Like other elements, silver originates on land and makes its way into the oceans primarily through weathering, where rainwater washes elements from rocks and carries them into rivers. Certain ocean regions become enriched with silver due to river inflow, atmospheric dust, human emissions, and hydrothermal vents. In its ionic form (Ag+), silver is toxic to marine life. However, very little is known about how it interacts with broader oceanic ecosystems, Mr. Xu pointed out.
To learn more about how silver behaves in marine environments, Xu and his colleagues analyzed sediment cores from an upwelling zone in Vietnam, located in the eastern part of the South China Sea. Upwelling zones are coastal areas where cold water rises from the ocean floor, bringing nutrients that support surface ecosystems.
The researchers divided the sediment core from the upwelling zone into two sections. The concentration of silver decreased from the base of the core, dated to around 1200 B.C., up to 7 centimeters from the top. However, the upper section of the core displayed a completely different trend. “The burial of silver over the last 3,200 years shows a sharp increase around 1850,” the authors wrote in their report. This period aligns with a rise in significant CO2 emissions into the atmosphere.
Silver concentrations in upwelling zones are typically high. The scientists noted that the level of silver off the coast of Vietnam was naturally elevated and comparable to levels previously recorded in upwelling areas off Canada, Mexico, Peru, and Chile. However, those studies did not link high silver concentrations to global warming, the researchers clarified.
Global warming raises water temperatures and intensifies coastal winds, which together increase the intensity of upwelling. This results in more nutrients being brought to the surface, boosting algal blooms that support the entire food chain. High levels of dissolved silver in these regions may mean that organisms absorb it more than in other areas. When they eventually die and sink, silver settles on the ocean floor.
“Silver enters sediments along with organic matter. Deep-water upwellings are intensified due to global warming, and we believe that the silver content in sediments across all these areas is increasing,” explained Lichuan Xu. “High levels of silver in sediments have the potential to leach back into seawater,” he noted. If this occurs on a global scale, it could pose a problem, as silver could potentially leach out and poison ocean ecosystems. If silver does not enter the water, it will eventually find its way back to land, the study’s authors believe. “Nothing is truly lost; it just gets moved around,” they stated.
The results of the study were published in the journal Geophysical Research Letters.