Sediment controls dynamic behavior of a Cordilleran Ice Stream at the Last Glacial Maximum

• Published in: Nature Communications
• Main Authors: Cowan, Ellen A, Zellers, Sarah D, Muller, Juliane, Walczak, M H, Worthington, Lindsay L, Caissie, Beth E, Clary, Wesley A, Jaeger, John M, Gulick, Sean P S, Pratt, Jacob W, Mix, Alan C, Fallon, Stewart
• Format: Article in Journal/Newspaper
• Language: English
• Published: Macmillan Publishers Ltd
• Subjects: Ice Sheet; Tidewater
• Online Access: http://hdl.handle.net/1885/219259; https://doi.org/10.1038/s41467-020-15579-0; https://openresearch-repository.anu.edu.au/bitstream/1885/219259/3/01_Cowan_Sediment_controls_dynamic_2020.pdf.jpg

The uncertain response of marine terminating outlet glaciers to climate change at time scales beyond short-term observation limits models of future sea level rise. At temperate tidewater margins, abundant subglacial meltwater forms morainal banks (marine shoals) or ice-contact deltas that reduce water depth, stabilizing grounding lines and slowing or reversing glacial retreat. Here we present a radiocarbon-dated record from Integrated Ocean Drilling Program (IODP) Site U1421 that tracks the terminus of the largest Alaskan Cordilleran Ice Sheet outlet glacier during Last Glacial Maximum climate transitions. Sedimentation rates, ice-rafted debris, and microfossil and biogeochemical proxies, show repeated abrupt collapses and slow advances typical of the tidewater glacier cycle observed in modern systems. When global sea level rise exceeded the local rate of bank building, the cycle of readvances stopped leading to irreversible retreat. These results support theory that suggests sediment dynamics can control tidewater terminus position on an open shelf under temperate conditions delaying climate-driven retreat Funding was provided by the National Science Foundation award OCE1434945 and a post-expedition award from the U.S. Science Support Program of IODP to E.A.C. J.M. received funding from the German Research Foundation (MU3670/1-2) and a Helmholtz Research grant (VH-NG-1101). S.D.Z. received funding from the University of Central Missouri Center for Teaching and Learning. M.H.W. and S.J.F. acknowledge support from the Australian IODP office, Australian Research Council, and American Australian Association. This is the University of Texas Institute for Geophysics Contribution #3644.