The silicon cycle impacted by past ice sheets

• Published in: Nature Communications
• Main Authors: Hawkings, Jon R., Hatton, Jade E., Hendry, Katharine R., de Souza, Gregory F., Wadham, Jemma L., Ivanovic, Ruza F, Kohler, Tyler J., Stibal, Marek, Beaton, Alexander, Lamarche-Gagnon, Guillaume, Tedstone, Andrew, Hain, Mathis P., Bagshaw, Elizabeth, Pike, Jennifer, Tranter, Martyn
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2018
• Subjects: glacier; Greenland; Ice Sheet; Iceland
• Online Access: https://hdl.handle.net/1983/ab76f347-c76a-4bea-bf82-738b6043e7b9; https://research-information.bris.ac.uk/en/publications/ab76f347-c76a-4bea-bf82-738b6043e7b9; https://doi.org/10.1038/s41467-018-05689-1; https://research-information.bris.ac.uk/ws/files/164742921/hawkings2018.pdf; http://www.scopus.com/inward/record.url?scp=85051530962&partnerID=8YFLogxK

Globally averaged riverine silicon (Si) concentrations and isotope composition (δ 30 Si) may be affected by the expansion and retreat of large ice sheets during glacial−interglacial cycles. Here we provide evidence of this based on the δ 30 Si composition of meltwater runoff from a Greenland Ice Sheet catchment. Glacier runoff has the lightest δ 30 Si measured in running waters (−0.25 ± 0.12‰), significantly lower than nonglacial rivers (1.25 ± 0.68‰), such that the overall decline in glacial runoff since the Last Glacial Maximum (LGM) may explain 0.06–0.17‰ of the observed ocean δ 30 Si rise (0.5–1.0‰). A marine sediment core proximal to Iceland provides further evidence for transient, low-δ 30 Si meltwater pulses during glacial termination. Diatom Si uptake during the LGM was likely similar to present day due to an expanded Si inventory, which raises the possibility of a feedback between ice sheet expansion, enhanced Si export to the ocean and reduced CO 2 concentration in the atmosphere, because of the importance of diatoms in the biological carbon pump.