The silicon cycle impacted by past ice sheets

• Main Authors: Hawkings, Jon R., Hatton, Jade E., Hendry, Katharine R., De Souza, Gregory, id_orcid:0 000-0002-0232-2690, Wadham, Jemma, Ivanovic, Ruza, 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: Nature 2018
• Subjects: Greenland; glacier; Ice Sheet; Iceland
• Online Access: https://hdl.handle.net/20.500.11850/283991; https://doi.org/10.3929/ethz-b-000283991

Globally averaged riverine silicon (Si) concentrations and isotope composition (δ30Si) 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 δ30Si composition of meltwater runoff from a Greenland Ice Sheet catchment. Glacier runoff has the lightest δ30Si 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 δ30Si rise (0.5–1.0‰). A marine sediment core proximal to Iceland provides further evidence for transient, low-δ30Si 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 CO2 concentration in the atmosphere, because of the importance of diatoms in the biological carbon pump. ISSN:2041-1723