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, Kohler, Tyler J., Stibal, Marek, Beaton, Alexander, Lamarche-Gagnon, Guillaume, Tedstone, Andrew, Hain, Mathis P., Bagshaw, Elizabeth, Pike, Jennifer, Tranter, Martyn
• Format: Text
• Language: English
• Published: Nature Publishing Group UK 2018
• Subjects: Article; Greenland; glacier; Ice Sheet; Iceland
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6086862/; http://www.ncbi.nlm.nih.gov/pubmed/30097566; https://doi.org/10.1038/s41467-018-05689-1

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.