188宝金博页面版

The Cryosphere, 19, 2779–2795, 2025https://doi.org/10.5194/tc-19-2779-2025© Author(s) 2025. This work is distributed underthe Creative Commons Attribution 4.0 License.Sediment transport capacity response to variations in waterdischarge in pressurized subglacial channelsIan Delaney 1 , Andrew J. Tedstone 1,2 , Mauro A. Werder 3,4 , and Daniel Farinotti 3,41 Institut des dynamiques de la surface terrestre (IDYST), Université de Lausanne,Bâtiment Géopolis, 1015 Lausanne, Switzerland2 Department of Geosciences, University of Fribourg, Ch. du Musée 1700, Fribourg, Switzerland3 Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH-Zürich,Hönggerbergring 26, 8093 Zurich, Switzerland4 Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), bâtiment ALPOLE, Sion, SwitzerlandCorrespondence: Ian Delaney (IanArburua.Delaney@unil.ch)Received: 15 August 2024 –Discussion started: 11 September 2024Revised: 9 April 2025 –Accepted: 11 April 2025 –Published: 4 August 2025Abstract. Sediment transport capacity in both subaerial andsubglacial channels depends on the shear stress exertedacross the channel bottom, which varies with water veloc-ity and channel width. In fully subaerial channels, water dis-charge variations are accommodated by f l ow depth and widthchanges along with water velocity. However, in subglacialchannels, water is pressurized by the ice above, and theygrowinresponsetothefrictionalheatingofthewaterf l owingthrough them. As a result, rapid changes in water dischargemainly result in velocity variations, as the channel geome-try evolves slowly. Here, we present formulations of sedi-ment transport capacity in different channel types and applysubglacial and subaerial hydraulics models to hydrographsfrom an Alpine glacier and a catchment of the Greenland IceSheet. Numerical experiments show that changing channelsize results in sediment transport capacity peaking before themaximum water discharge. This hysteresis causes a highlyvariable relationship between sediment and water dischargein a transport-limited subglacial system. The results also in-dicate that high subglacial sediment transport capacities canoccur across a wide range of water discharges. Reducing wa-ter discharge variability by smoothing lessens the hysteresiseffects, insome cases to the point where a covarying relation-ship between water discharge and sediment transport capac-ity can be approached, similar to subaerial systems. A secondset of numerical experiments shows that subglacial sedimenttransport is highly non-linear with respect to water discharge,creating more variability in sediment transport capacity. Yet,the results and formulations of subglacial sediment transportcapacity show that its variability can approach that of sub-aerial systems when subglacial channel size is in equilibriumwith water discharge. The implications of these f indings helpto evaluate sediment discharge from glaciers with differenthydro-climatic forcings and to establish sources of variabil-ity in sediment export–water discharge relationships. Thesef indings can improve the interpretation of sedimentdischargerecords in glacierized catchments.1 IntroductionChanges in glacier dynamics and hydrology have motivatednumerous recent studies on sediment transport processes incold regions (e.g. Li et al., 2022; Vergara et al., 2022; Zhanget al., 2022). Increases in sediment transport have been ob-served in Greenland (Bendixen et al., 2017), the EuropeanAlps (Costa et al., 2018), the Himalayas (Li et al., 2021), andthe Andes (Vergara et al., 2022). To accurately explain theobserved changes in sediment transport in glacierized catch-ments, the processes controlling sediment discharge and itsvariations with water discharge need to be examined (e.g. Ri-ihimaki et al., 2005; Swift et al., 2005).Glacier abrasion and quarrying sculpt landscapes and cre-ate sediment that is transported f l uvially over periods of mil-lennia or longer (cf. Hallet, 1979; Iverson, 2012; Ugelviget al., 2018). Pressurized subglacial water can transportPublished by Copernicus Publications on behalf of the European Geosciences Union.