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: Just a few minutes of freezing and thawing can have a decisive impact on how ferrihydrite, the most reactive iron mineral in cold soils, permafrost and glaciers, transforms, according to researchers at Umeå University. As climate warming intensifies freeze-thaw cycles and extends them into new regions, ice is becoming an increasingly important driver of Earth's ecosystems.
"Ice is not a passive freezer but an active geochemical reactor that can alter how an iron mineral transforms in just a few minutes," says Professor Jean-François Boily of the Department of Chemistry at Umeå University, who led the study published in Science. Ice is not simply a frozen block of water. In nature, ice can lock in a wide range of compounds, including minerals and organic carbon.
Among the most consequential of these are the iron minerals, because what happens to them while they are trapped in ice determines how iron behaves once the ice melts. Iron is one of the most abundant elements in Earth's crust and an essential metal for most living organisms. As rocks weather, iron is released and reacts with oxygen and water to form secondary iron minerals.
These iron oxides are found across vast areas of the Earth's surface. They can be seen as rust-colored coatings on rocks and as fine particles in soil, but they are also present in aquatic environments and in the atmosphere. Changes in how iron is released can have cascading effects throughout ecosystems, from mountain streams to Arctic coastal regions.
In the current study, the researchers investigated ferrihydrite, a poorly ordered iron oxide only a few nanometers in size. Ferrihydrite is the dominant reactive iron phase in glacial sediments, icebergs and cold soils. Its large surface area allows it to bind substantial amounts of nutrients, pollutants and organic carbon.
Whether ferrihydrite retains its reactive surface or transforms into a less reactive mineral determines how much bioavailable iron reaches polar oceans and how much carbon remains stored in frozen ground. When water freezes, microscopic pockets of liquid form between the growing ice crystals. Substances that cannot be incorporated into the ice become concentrated within these pockets.
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