Study Links West Antarctic Ice Sheet Changes to Reduced Carbon Absorption in Southern Ocean

Recent research published in Nature Geoscience reveals that fluctuations in the West Antarctic Ice Sheet (WAIS) are closely associated with marine algae growth in the Southern Ocean, though not as previously anticipated. The study identifies iron-rich sediments, transported by icebergs from West Antarctica, as a pivotal factor.

Iron typically acts as a fertilizer for algae. However, analysis of a sediment core from the Pacific sector of the Southern Ocean, retrieved in 2001 from over three miles below the surface, showed that increased iron supply did not enhance marine algae growth. Lead author Torben Struve of the University of Oldenburg noted,

"Normally, an increased supply of iron in the Southern Ocean would stimulate algae growth, which increases the oceanic uptake of carbon dioxide."

The research team attributed this anomaly to the chemical composition of the iceberg-delivered sediment. Their analyses suggest that the minerals were highly "weathered," rendering much of the iron less soluble and, consequently, less bioavailable to algae.

These findings suggest that continued shrinkage of the WAIS due to climate change could lead to reduced carbon dioxide absorption in the Southern Ocean. Co-author Gisela Winckler, a professor at the Columbia Climate School and a geochemist at the Lamont-Doherty Earth Observatory, emphasized,

"This reminds us that the ocean's ability to absorb carbon isn't fixed."

The study also sheds light on the sensitivity of the WAIS to climate change. Struve highlighted that during the last interglacial period, approximately 130,000 years ago, when temperatures were similar to today's, significant ice loss occurred in West Antarctica. He stated,

"Our results also suggest that a lot of ice was lost in West Antarctica at that time."

The disintegration of the ice sheet led to the release of numerous icebergs carrying weathered minerals into the Southern Ocean, which did not promote algae growth. Winckler pointed out,

"What matters here is not just how much iron enters the ocean, but the chemical form it takes."

Looking ahead, continued thinning of the WAIS could accelerate the erosion of weathered rock layers by glaciers and icebergs, potentially reducing carbon uptake in the Pacific sector of the Southern Ocean and further amplifying climate change. Struve cautioned,

"Based on what we know so far, the ice sheet is not likely to collapse in the near future, but we can see that the ice there is already thinning."

This research underscores the complex interactions between ice sheet dynamics and oceanic carbon cycles, highlighting the need for further studies to understand and predict future climate impacts.