Thinning ice in Antarctica could boost oceanic carbon absorption

A research team including the University believe their findings could help the Southern Ocean absorb more CO2 from the atmosphere
Research was conducted in East Antarctica, close to the Belgian Princess Elisabeth Antarctica Research Station

Thinning ice in Antarctica could boost oceanic carbon absorption

A research team including the University believe their findings could help the Southern Ocean absorb more CO2 from the atmosphere
Kate Winter
Research was conducted in East Antarctica, close to the Belgian Princess Elisabeth Antarctica Research Station

Research involving scientists from the University of Plymouth has shed new light on natural processes in East Antarctica that could, over long timescales, help the Southern Ocean absorb more carbon dioxide from the atmosphere.
As Antarctica's ice sheets thin due to climate change, newly exposed mountain peaks could significantly increase the supply of vital nutrients to the Southern Ocean which surrounds the continent. This could potentially enhance its ability to absorb atmospheric carbon dioxide, according to the study published in Nature Communications.
A team of scientists with expertise in oceanography, ice sheet modelling and geochemistry contributed to the study which looked at analysis of sediment samples from East Antarctica's Sør Rondane Mountains.
They discovered that weathered rocks exposed above the ice surface contain iron concentrations up to ten times higher than previously reported from the Antarctic continent. This bioavailable iron is transported to the ocean by glaciers and icebergs, where it fuels the growth of phytoplankton – microscopic marine organisms that absorb CO₂ through photosynthesis.
The research builds on earlier work involving University of Plymouth co-author Dr Matt Westoby, Associate Professor of Physical Geography in the University of Plymouth’s School of Geography, Earth and Environmental Sciences, which sought to establish how ice sheet surfaces had changed over time, and how this affects the release of debris from mountain peaks and its transfer into glacier systems.

Antarctica is a slow but powerful delivery system for transporting glacially eroded sediments to the Southern Ocean.

We have shown that those sediments are rich in micronutrients that can potentially fuel phytoplankton growth, which in turn could help to draw down atmospheric carbon dioxide over thousands of years. These exciting findings raise new questions about just how much nutrient-rich sediment could be making its way, via glaciers, to the Southern Ocean at much larger continental scales, and the implications for regional and global climate.

Matt WestobyDr Matt Westoby
Associate Professor of Physical Geography

The study found that sediments from mountain peaks protruding through the ice – known as nunataks – had over three times more extractable iron compared to sediments already being transported by glaciers. Some visibly rust-stained rock samples showed particularly elevated iron levels, suggesting that weathering processes on exposed surfaces create especially nutrient-rich material.
"Our results show that exposed bedrock in Antarctica acts like an iron factory," explained Dr Kate Winter, Associate Professor in the School of Geography and Natural Sciences at Northumbria University and lead author of the research paper. "Even though air temperatures rarely rise above freezing, sunlight can heat dark rock surfaces above 20°C in summer, creating the conditions needed for weathering and the formation of bioavailable iron compounds."
Satellite observations confirm that coastal waters near to glacier outlets in the study region experience recurring phytoplankton blooms, demonstrating the biological importance of this natural iron delivery system. The blooms contribute to the Southern Ocean's role as a major carbon sink, absorbing atmospheric CO₂.

The exciting thing is that we can take some hope from these findings because we know that carbon dioxide is a really important factor in climate change. From our research we now know that sediments from the Antarctic continent could help to draw down atmospheric carbon dioxide into the ocean. Whilst our study area is limited to one glacier system, what we need to understand is the potential impact of these many small amounts being drawn down together across the whole of Antarctica. Piecing together information to gather an accurate picture of how much these natural systems are working to reduce the amount of carbon in the atmosphere is crucial.

Ketelers_Glacier.JPG

Dr Kate Winter
Associate Professor in the School of Geography and Natural Sciences at Northumbria University
 

The sun heats up mountains in Antarctica, helping them to break down and deliver smaller rock fragments to glaciers below Kate Winter
The sun heats up mountains in Antarctica, helping them to break down and deliver smaller rock fragments to glaciers below
However the research team, which also includes scientists from the universities of Newcastle, Swansea, Edinburgh and Leeds, caution that there is a significant time lag in this process. Using ice flow models, they calculated that it takes between 10,000 and 100,000 years for iron-rich sediments collected in the mountains to reach the coast via glacial transport.
The study suggests that as temperatures continue to rise, several factors will increase iron delivery to the Southern Ocean:
  • More mountain peaks will emerge as ice sheets thin.
  • Increased rock slope failures will deliver more sediment to glaciers.
  • Enhanced weathering will produce more bioavailable iron compounds.
  • Icebergs carrying this iron-rich sediment will distribute nutrients across vast ocean areas.
The research provides important insights into how Antarctica's extreme environment connects with ocean ecosystems and the global carbon cycle. It also offers a glimpse into how this system may evolve as climate change continues to reshape the continent.
  • The full study - Winter et al: Thinning Antarctic glaciers expose high-altitude nunataks delivering more bioavailable iron to the Southern Ocean - is published in Nature Communications. DOI: 10.1038/s41467-025-65714-y.
 

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