Melting Antarctic Glaciers Provide Less Iron to Southern Ocean Than Expected

New study finds most iron in the region comes from deep ocean water and sediments, not glacial meltwater

Mar. 3, 2026 at 6:47am

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A new study from Rutgers University-New Brunswick has found that melting Antarctic glaciers contribute far less iron to the surrounding Southern Ocean than previously believed. The researchers measured iron levels in glacial meltwater and found that only about 10% of the dissolved iron flowing out of the ice shelf cavity came from the meltwater itself. The majority of the iron originated from deep ocean water (62%) and sediments on the continental shelf (28%). This challenges long-standing assumptions about iron sources in the Southern Ocean as the planet warms.

Why it matters

The Southern Ocean is a critical carbon sink, with abundant phytoplankton growth that removes large quantities of carbon dioxide from the atmosphere. It was widely believed that as Antarctic glaciers melt, the release of iron trapped in the ice would fuel these phytoplankton blooms, providing a potential climate change mitigation. However, this new research suggests that mechanism may not be as significant as previously thought, raising questions about how climate change models should account for iron sources in the region.

The details

The Rutgers-led research team traveled to the Dotson Ice Shelf in the Amundsen Sea of West Antarctica in 2022 to collect direct measurements of glacial meltwater and its iron content. They found that the meltwater accounted for only about 10% of the dissolved iron flowing out of the ice shelf cavity, with the majority coming from deep ocean water (62%) and continental shelf sediments (28%). The isotopic signatures of the iron also pointed to processes occurring beneath the glacier itself, where a liquid meltwater layer may be dissolving iron from bedrock more effectively than the melting ice.

  • In 2022, the research team traveled to the Dotson Ice Shelf in the Amundsen Sea of West Antarctica.
  • The study was published in Communications Earth and Environment in February 2026.

The players

Rutgers University-New Brunswick

The university where the lead researcher, Rob Sherrell, is a professor in the Department of Marine and Coastal Sciences at the School of Environmental and Biological Sciences.

Rob Sherrell

The principal investigator of the study and a professor at Rutgers University-New Brunswick.

Venkatesh Chinni

The lead author of the study and a postdoctoral scholar at Rutgers University-New Brunswick.

Jessica Fitzsimmons

A collaborator on the study from Texas A&M University who examined isotopic ratios to trace the origin of the iron.

Janelle Steffen

A collaborator on the study from Texas A&M University who performed the initial isotopic analyses in the laboratory of Tim Conway at the University of South Florida.

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What they’re saying

“It has been widely assumed that glacial melting underneath ice shelves contributes considerable bioavailable iron to these shelf waters, in a process of natural glacier-driven iron fertilization.”

— Rob Sherrell, Professor, Department of Marine and Coastal Sciences, Rutgers School of Environmental and Biological Sciences

“Roughly 90% of the dissolved iron coming out of the ice shelf cavity comes from deep waters and sediments outside the cavity, not from meltwater.”

— Venkatesh Chinni, Lead author, postdoctoral scholar at Rutgers University-New Brunswick

What’s next

The researchers emphasize that more work is needed to fully understand how subglacial processes influence iron release in the Southern Ocean as the planet warms. This new data could lead to revisions in climate change forecasts and models that have long assumed glacial meltwater as a significant source of iron in the region.

The takeaway

This study challenges a widely held belief about the potential climate benefits of melting Antarctic glaciers, showing that the iron they release may not be as significant as previously thought. It highlights the importance of direct field measurements to validate climate models and improve our understanding of complex Earth system processes.