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Ice‘s Unexpected Role in Iron Dissolution and Arctic River Discoloration
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New research reveals ice dissolves iron minerals more effectively than liquid water, impacting Arctic ecosystems.
By Amelia Richards | OSLO – 2025/09/23 13:25:26
A recent study from Umeå University has found that ice can dissolve iron minerals more efficiently than liquid water. This revelation offers a potential clarification for the increasing prevalence of rusty orange coloration in Arctic rivers as permafrost thaws due to climate change.
The study, published in the journal PNAS, demonstrates that ice at -10 degrees Celsius releases more iron from common minerals compared to liquid water at 4 degrees Celsius. this finding challenges the conventional understanding that chemical reactions slow down in frozen environments.
“It may sound counterintuitive, but ice is not a passive frozen block,” says Jean-François Boily, Professor at Umeå University and co-author of the study. “Freezing creates microscopic pockets of liquid water between ice crystals. these act like chemical reactors, where compounds become concentrated and extremely acidic. This means they can react with iron minerals even at temperatures as low as minus 30 degrees Celsius.”
Researchers examined goethite, a common iron oxide mineral, alongside a naturally occurring organic acid, utilizing advanced microscopy and experimentation to gain insights into the process.
The study revealed that repeated freeze-thaw cycles enhance iron dissolution.As ice undergoes freezing and thawing, organic compounds previously trapped within the ice are released, thereby fueling further chemical reactions. Salinity also plays a significant role; fresh and brackish water promote dissolution, while seawater tends to suppress it.
These findings are particularly relevant to acidic environments, including mine drainage sites, frozen atmospheric dust, acid sulfate soils along the Baltic Sea coast, and any acidic frozen habitat where iron minerals interact with organic matter. The next phase of research will focus on determining weather these findings apply to all iron-bearing ice.
“Each cycle releases iron from soils and permafrost into the water. This can affect water quality and aquatic ecosystems across vast areas.”
“As the climate warms, freeze-thaw cycles become more frequent,” says Angelo Pio Sebaaly, doctoral student and first author of the study. “Each cycle releases iron from soils and permafrost into the water. This can affect water quality and aquatic ecosystems across vast areas.”
The study underscores that ice is not merely a passive storage medium but an active participant in environmental processes. The increasing frequency of freezing and thawing in polar and mountain regions could have significant consequences for ecosystems and the natural cycling of elements.
Frequently Asked Questions
- Why are Arctic rivers turning orange?
- The discoloration is likely due to increased iron dissolution from thawing permafrost, as iron oxides are released into the water. USGS EPA
- What is goethite?
- Goethite is a common iron oxide mineral found in soils and rocks, often contributing to the reddish-brown color of soil. Mindat.org Britannica
- How does salinity affect iron dissolution in ice?
- fresh and brackish water tend to increase iron dissolution, while seawater can suppress it. Science.org Nature.com
Sources
- Umeå University Study Published in PNAS
- USGS – Iron and Water
- NOAA Climate.gov – Arctic Report Card 2023
