Late Holocene Glacial Lake Outburst Floods (GLOFs) in Chilean Patagonia: evidence from Valle Grande floodplain sediments (47 °S)
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Date
2019-07-30
Journal Title
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Publisher
International Union for Quaternary Research (INQUA)
Abstract
Glacial Lake Outburst Floods (GLOFs) constitute a major threat in glacierized regions. These catastrophic events occur when a lake dammed by a glacier or moraine empties, resulting in abrupt flooding. In Patagonia, this issue is particularly pronounced in the Baker region (47–48°S), where 21 GLOFs have been documented in the last decade. All recent GLOFs resulted from the emptying of Cachet 2 Lake into Colonia River, a tributary of the Baker River. During such events, Baker River, which is the largest in Chile draining most of the eastern side of the Northern Patagonian Icefield, triples in discharge. Due to backwater flooding, the water level in the Valle Grande floodplain, which is located along Baker river immediately upstream of Colonia River, rises by 4 to 6 meters, resulting in its complete inundation. Although GLOF frequency seems to have increased worldwide in the last decades, there is currently no reliable scientific evidence supporting this claim, largely due to a lack of flood records on timescales that extend beyond gauged river-flow datasets. To examine changes in GLOF frequency in Patagonia, four sediment cores were collected in the Valle Grande floodplain. The cores were scanned on a Geotek MSCL at 2 mm resolution for magnetic susceptibility (MS), gamma density, and sediment color (spectrophotometry). Loss-on-ignition was measured continuously at 5 mm resolution and radiocarbon ages, 210Pb concentrations, and charcoal counts were obtained to establish a core chronology. All cores indicate the occurrence of fine-grained organic-poor material with high MS and density values, alternating with organic-rich deposits. It is hypothesized that the fine-grained material is deposited during floods, whereas the organic-rich soils represent periods of quiescence. The records seem to display three periods rich in floods during the last 2500 years. Once precise age depth models are constructed, the results will be compared to historical records of climate and glacier variability to assess the possible relationship between GLOFs and climate change.
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Keywords
Quaternary period, Glaciers, Floods, Chile, Rivers, Drill cores, Data
Citation
Vandekerkhove, E., Bertrand, S., Reid, B., Mauquoy, D., Saunders, K. M., McWethy. D., Stammen, S., & Torrejón, F. (2019). Late Holocene Glacial Lake Outburst Floods (GLOFs) in Chilean Patagonia: evidence from Valle Grande floodplain sediments (47 °S). Poster presented to the 20th INQUA Congress, 25th - 31st July 2019, Dublin, Ireland. Retrieved from: https://virtual.oxfordabstracts.com/#/event/public/574/submission/1678