This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Over the past 230,000 years, the growth and retreat of the Icelandic ice sheet have led to major changes in the seawater chemistry of the North Atlantic, caused by the interaction between volcanism and ice in Iceland. Scientists at the Institute of Environmental Physics at Heidelberg University have demonstrated this using sediment cores from the northeastern Atlantic—the Rockall Plateau.
The researchers analyzed the isotopic composition of the rare-earth element neodymium in these drill cores. According to their findings, the isotopic signal fluctuated significantly over the course of glacial and interglacial periods, following the "rhythm" of the ice ages, as shown by the studies led by Dr. The isotopic composition of neodymium (Nd) in seawater is one of the most commonly used tools for reconstructing how ocean circulation has changed in the recent geological past.
The method is based on the central assumption that the chemical "fingerprints" characteristic of the composition of large water masses have remained largely constant over time. Research by the Heidelberg scientists now suggests that this fixed isotopic composition no longer applies to the North Atlantic during glacial periods. The research is published in the journal Science Advances.
Their analyses of deep-sea sediments from the Rockall Plateau show that the chemistry of North Atlantic seawater has changed repeatedly and significantly. The researchers attribute these changes to volcanic material from Iceland. Their investigations are based on the fact that different types of continental rock exhibit different isotopic signatures.
The ratio of the specific isotopes 143Nd and 144Nd of neodymium dissolved in seawater reflects the rocks from which the rare-earth element was extracted. As the ice sheet in Iceland advanced during a glacial period and carved its way through the Icelandic basaltic bedrock, it produced large quantities of fine, highly reactive rock dust. This material was released into the surrounding North Atlantic Ocean, where it dissolved and released neodymium with a distinct radiogenic signature—enriched in 143Nd.
Analysis of neodymium isotopes from the ODP Site 982 sediment core on the Rockall Plateau shows that the upper water masses of the North Atlantic were consistently much more radiogenic during glacial maxima than during the warm interglacial periods, and that these fluctuations correlated closely with the volume of the Icelandic ice sheet. The Heidelberg scientists developed a so-called box model that allowed them to reproduce their analyses of the deep-sea sediment samples. According to the model, the changes in seawater chemistry resulting from volcanic input were not strongly linear but instead responded to the dynamics of the ice in Iceland—they peaked during periods of rapid glaciation.
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