Volcanic ash as an oceanic iron source and sink

• Published in: Geophysical Research Letters
• Main Authors: Rogan, Nicholas, Achterberg, Eric P., Le Moigne, Frederic A. C., Marsay, Chris M., Tagliabue, Alessandro, Williams, Richard G.
• Format: Article in Journal/Newspaper
• Language: English
• Published: AGU (American Geophysical Union) 2016
• Subjects: Eyjafjallajökull; North Atlantic
• Online Access: https://oceanrep.geomar.de/id/eprint/31714/; https://oceanrep.geomar.de/id/eprint/31714/7/Rogan.pdf; https://doi.org/10.1002/2016GL067905

Volcanic ash deposition to the ocean forms a natural source of iron (Fe) to surface water microbial communities. Inputs of lithogenic material may also facilitate Fe removal through scavenging. Combining dissolved Fe (dFe) and thorium-234 observations alongside modelling, we investigate scavenging of Fe in the North Atlantic following the Eyjafjallajökull volcanic eruption. Under typical conditions biogenic particles dominate scavenging, whereas ash particles dominate during the eruption. The size of particles is important as smaller scavenging particles can become saturated with surface-associated ions. Model simulations indicate that ash deposition associated with Eyjafjallajökull likely led to net Fe removal. Our model suggests a three-fold greater stimulation of biological activity if ash deposition had occurred later in the growing season when the region was Fe-limited. The implications of ash particle-scavenging, eruption timing and particle saturation need to be considered when assessing the impact of ash deposition on the ocean Fe cycle and productivity.