Ice isn’t as inert as it looks. A new study from Umeå University reveals that freezing conditions dramatically speed up the release of iron from minerals — at rates that current environmental models may be severely underestimating.
Ice has long been treated as a passive bystander in environmental chemistry — a frozen pause between seasons. But a study published in the Proceedings of the National Academy of Sciences on April 22 challenges that assumption, showing that ice actively accelerates the breakdown of iron minerals and may be pumping far more iron into ecosystems than scientists currently account for.
The research, led by Jean-François Boily, a professor of chemistry at Umeå University in Sweden, focuses on goethite, a rust-colored iron mineral commonly found in soils, sediments and atmospheric dust. Using controlled laboratory experiments, Boily’s team measured how quickly goethite dissolved in both liquid water and ice under the influence of various dissolved salts — compounds that occur naturally throughout the environment.
A Clear and Striking Pattern
The findings were sharper than the researchers anticipated. Boily described the outcome as straightforward.
“The result was remarkably clear. Ice boosted the dissolution rate for every salt that binds to iron, and the stronger the binding, the greater the boost,” Boily said in a news release.
Fluoride, which binds tightly to iron, released more than four times as much iron when dissolved in ice compared with liquid water. Sulfate, a weaker binder, produced a smaller but still measurable increase. Perchlorate, which barely interacts with iron at all, showed no dissolution effect in either phase. The relationship between binding strength and ice-driven release was consistent enough to suggest a broader predictive rule.
“This reveals a simple rule: If you know how strongly a substance binds to iron, you can likely estimate how much ice will amplify its.” Boily added.
What Happens Inside the Ice
The chemistry behind this effect comes down to what happens at a microscopic level when water freezes. As ice crystals form, dissolved salts and other substances that can’t fit into the crystal lattice get pushed into tiny liquid pockets trapped between the crystals. Within these microscale environments, concentrations of salts can surge up to 500 times higher than in the surrounding bulk solution — creating intensely reactive hot spots where mineral dissolution accelerates dramatically.
This concentration effect helps explain why the iron release rates in ice so far outpace those in liquid water, and why the phenomenon scales with binding affinity.
“What surprised us most was how consistent this effect appeared across the compounds we tested. If the pattern holds more broadly, we could potentially predict ice-enhanced mineral breakdown based on a single chemical property. That would be a valuable tool for environmental modeling,” added Boily.
Why It Matters for the Planet’s Future
About 17% of Earth’s land surface sits atop permafrost, and vast additional regions undergo seasonal freeze-thaw cycles every year. As global temperatures rise, those cycles are becoming more frequent and permafrost is thawing at an accelerating pace — meaning that ice-driven chemical reactions could be playing out across enormous swaths of the planet.
Iron is not a background element in these systems. It controls algae growth in lakes and oceans, helps bind carbon in soils, and influences water color and quality in streams and rivers. Shifts in how much iron gets released — and how quickly — can set off cascading effects that ripple from mountain headwaters to Arctic coastlines. Those effects include changes in aquatic food webs, carbon storage capacity, and even drinking water chemistry.
Boily emphasized that understanding this chemistry is essential for building accurate climate projections.
“To understand how climate change affects natural systems, we also need to understand the chemistry inside ice,” he said.
Implications for Students and Researchers
For students studying environmental science, chemistry or climate policy, this research underscores a recurring theme in earth science: the processes that look the simplest on the surface — ice forming and melting — often conceal complex chemistry with global consequences. Models that ignore ice-phase reactions may be systematically undercounting iron flux, which could skew projections for nutrient cycling, carbon budgets and water quality across some of the world’s most climate-sensitive regions.
The study also points toward a practical path forward. If a single chemical property — how strongly a substance binds to iron — can reliably predict how much ice will amplify its dissolution, that principle could be incorporated into next-generation environmental models without requiring exhaustive case-by-case testing.
Source: Umeå University