Declining discharge of glacier outburst floods through the Holocene in central Patagonia. (15th March 2021)

• Record Type: Journal Article
• Authors: Benito, Gerardo; Thorndycraft, Varyl R.; Medialdea, Alicia; Machado, Maria J.; Sancho, Carlos; Dussaillant, Alejandro
• Is Part Of: Quaternary science reviews. Volume 256(2021)
• Publication Date: 2021-03-15
• Subjects: Geomorphology -- GLOFs -- Palaeohydrology -- Palaeosols -- South America; Geology, Stratigraphic -- Quaternary -- Periodicals; Stratigraphie -- Quaternaire -- Périodiques; 551.79
• DOI: 10.1016/j.quascirev.2021.106810
• Languages: English
• ISSNs: 0277-3791

Abstract

Abstract: Glacier outburst floods are a major hazard in glacierized catchments. Global analyses have shown reduced frequency of glacier floods over recent decades but there is limited longer-term data on event magnitude and frequency. Here, we present a Holocene palaeoflood record from the Río Baker (Chilean Patagonia), quantifying the discharge and timing of glacier floods over millennial timescales. A catastrophic flood of 110, 000 m 3 /s (0.11 Sv) occurred at 9.6 ± 0.8 ka, during final stages of the Late Glacial Interglacial Transition, followed by five flood-phases coeval or post-dating Holocene neoglacials. Highest flood frequencies occurred at 4.3–4.4 ka, with 26 floods of minimum discharges of 10, 000–11, 000 m 3 /s, and 0.6 ka with 10 floods exceeding 4600–5700 m 3 /s. The largest modern outburst flood recorded surpassed ∼3810 m 3 /s. Thus glacier flood magnitude declines from the order of 0.1 to 0.01 Sv over the Early to Mid Holocene, and to 0.001 Sv in the instrumental record. Highlights: First bedrock gorge palaeoflood record of Holocene Glacial Lake Outburst Floods. GLOF frequency increased at the end or post-dating three Holocene neoglacials. Flood discharge (magnitude) declined from 0.1 Sv to 0.001 Sv through the Holocene. The decrease in peak GLOF magnitude reflects an indirect control of ice-sheet mass. Modern discharges are not exceptional in terms of the Baker valley Holocene record.