Journal
GEOMORPHOLOGY
Volume 408, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.geomorph.2022.108248
Keywords
Glacial geomorphology; Analog modeling; Subglacial hydrology; Subglacial bedforms; Scandinavia
Funding
- French Agence Nationale de la Recherche [ANR-18-CE01-0009]
- European Research Council (ERC) under European Union [787263]
- European Research Council (ERC) [787263] Funding Source: European Research Council (ERC)
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Research shows that bedforms in the bed of palaeo-ice sheets record fluctuations in meltwater discharge, highlighting the complex interactions between subglacial drainage, basal processes, and bedform development. Morphometric analysis reveals the progressive transformation of ribbed bedforms into murtoos, and provides a quantification of this transformation using two dimensionless morphometric parameters.
Fluctuations in meltwater discharge below modern glaciers and ice sheets due to diurnal, seasonal and long-term temperature variations are modulated by complex interactions between subglacial drainage, basal processes and bedform development. The bed of palaeo-ice sheets contains a variety of bedforms recording these modulations and provides an open window into the subglacial environment. Through the morphometric analysis of natural and experimental bedforms, respectively mapped along Scandinavian meltwater corridors and produced in a physical model simulating transitory subglacial water flow, we observe a morphological and genetic bedform continuum corresponding to the progressive transformation of ribbed bedforms into murtoos. Two alternating drainage configurations, related to repeated subglacial flooding events, are involved in this transformation: (i) significant meltwater discharge, high hydraulic connectivity and ice-bed decoupling during flooding events lead to hydraulic alteration of ribbed bedforms by erosion, sediment deposition and channel incision, while (ii) limited meltwater flow, low hydraulic connectivity and ice-bed recoupling that follow flooding events lead to their deformational reshaping into murtoos. The degree of transformation of ribbed bedforms into murtoos can be quantified by combining two dimensionless morphometric parameters (circularity and sinuosity) and provides a convenient proxy to constrain magnitudes, durations and/or frequencies of subglacial floods in palaeomeltwater corridors.
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