We extend recent work by applying hydrology models designed for global scale river routing to a basin on the GrIS. We show that large channels do not dewater overnight despite a lack of overnight melt input, and also show that we cannot match in situ measurements of river flux without first reducing the amount of modelled meltwater runoff generated in the catchment. These findings have implications for surface mass balance modelling and the eventual fate meltwater.
We extend recent work by applying hydrology models designed for global scale river routing to a...
Review status: this preprint is currently under review for the journal TC.
Hourly surface meltwater routing for a Greenlandic supraglacial
catchment across hillslopes and through a dense topological channel
network
Colin J. Gleason1,Kang Yang2,Dongmei Feng1,Laurence C. Smith3,4,Kai Liu5,Lincoln H. Pitcher6,Vena W. Chu7,Matthew G. Cooper8,Brandon T. Overstreet9,Asa K. Rennermalm10,and Jonathan C. Ryan3Colin J. Gleason et al.Colin J. Gleason1,Kang Yang2,Dongmei Feng1,Laurence C. Smith3,4,Kai Liu5,Lincoln H. Pitcher6,Vena W. Chu7,Matthew G. Cooper8,Brandon T. Overstreet9,Asa K. Rennermalm10,and Jonathan C. Ryan3
Received: 17 Sep 2020 – Accepted for review: 12 Oct 2020 – Discussion started: 16 Oct 2020
Abstract. Recent work has identified complex perennial supraglacial stream/river networks in areas of the Greenland Ice Sheet (GrIS) ablation zone. Current surface mass balance (SMB) models appear to overestimate meltwater runoff in these networks compared to in-channel measurements of supraglacial discharge. Here, we constrain SMB models using the Hillslope River Routing Model (HRR), a spatially explicit flow routing model used in terrestrial hydrology, in a 63 km2 supraglacial river catchment in southwest Greenland. HRR conserves water mass and momentum and explicitly accounts for hillslope routing, and we produce hourly flows for nearly 10,000 channels given inputs of an ice surface DEM, a remotely sensed supraglacial channel network, SMB-modelled runoff, and an in situ discharge dataset used for calibration. Model calibration yields a Nash Sutcliffe Efficiency as high as 0.92 and physically realistic parameters. We confirm earlier assertions that SMB runoff exceeds the conserved mass of water routed to match measured flows in this catchment (by 12–59 %) and that large channels do not dewater overnight despite a diurnal shutdown of SMB runoff production. We further test hillslope routing and network density controls on channel discharge and conclude that explicitly including hillslope flow and routing runoff through a realistically fine channel network produces the most accurate results. Modelling complex surface water processes is thus both possible and necessary to accurately simulate the timing and magnitude of supraglacial channel flows, and we highlight a need for additional in situ discharge datasets to better calibrate and apply this method elsewhere on the ice sheet.
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Short summary
We extend recent work by applying hydrology models designed for global scale river routing to a basin on the GrIS. We show that large channels do not dewater overnight despite a lack of overnight melt input, and also show that we cannot match in situ measurements of river flux without first reducing the amount of modelled meltwater runoff generated in the catchment. These findings have implications for surface mass balance modelling and the eventual fate meltwater.
We extend recent work by applying hydrology models designed for global scale river routing to a...