Seasonal evolution of the supraglacial drainage network at Humboldt Glacier, North Greenland, between 2016 and 2020 

Abstract

Abstract. Supraglacial rivers and lakes are important for the routing and storage of surface meltwater during the summer melt season across the Greenland Ice Sheet (GrIS), yet remain poorly mapped and quantified across the northern part of the ice sheet, which is rapidly losing mass. Here we produce, for the first time, a high-resolution record of the supraglacial drainage network (including both rivers and lakes) and its seasonal behaviour at Humboldt Glacier, a wide-outlet glacier draining a large hydrologic catchment (13,488 km2), spanning the period 2016 to 2020 using 10 m spatial resolution Sentinel-2 imagery. Our results reveal a perennially extensive yet interannually-variable supraglacial network extending from an elevation of 200 m a.s.l to a maximum of ~1440 m a.s.l recorded in 2020, with limited development of the network observed in the low melt years of 2017 and 2018. The supraglacial drainage network is shown to cover an area ranging between 965.7 km2 (2018) and 1566.3 km2 (2019) at its maximum seasonal extent, with spatial coverage of up to 2685 km2 recorded during the early phases of the melt season when a slush zone is most prominent. Up-glacier expansion and the development of an efficient supraglacial drainage network as surface runoff increases and the snowline retreats is clearly visible. Preconditioning of the ice surface following a high melt year is also observed, with the earlier widespread exposure of the supraglacial drainage network in 2020 compared to other years; a finding that may become representative with persistent warmer years into the future. Overall, this study provides evidence of a persistent, yet dynamic, supraglacial drainage network at this prominent northern GrIS outlet glacier and advances our understanding of such hydrologic processes, particularly under ongoing climatic warming and enhanced runoff.

A comparison of supraglacial meltwater features throughout contrasting melt seasons: Southwest Greenland

“…Slush was identified as large areas of dense, light blue meltwater with poorly defined boundaries (e.g. Rawlins et al, 2023). Rivers/streams were identified as narrow, linear meltwater features.…”

“…As high melt years like 2019 become more frequent, it is likely that slush will become more prevalent, leading to formation and expansion of ice slabs and thus the preconditioning of the ice sheet surface for ponding in future years. This is potentially already occurring at Humboldt Glacier in North Greenland where studies have shown earlier activation of the hydrologic system and longer melt-seasons in years following widespread slush events (Rawlins et al, 2023).…”

“…Although there have been a handful of studies that have focussed on mapping and analysing the supraglacial hydrological system as a whole (e.g. Rawlins et al, 2023;Zhang et al, 2023;Yang et al, 2021), the drainage of meltwater features was not considered.…”

Future runoff increase may destabilize Petermann ice shelf

“…At 79N, it has been suggested that the recent expansion of its central basal channel is a consequence of heightened Q sg , attributed to a signiĄcantly expanded surface melt area during summer, brought about by atmospheric warming (Narkevic et al, 2023;Zeising et al, 2023). Moreover, the extensive network of moulins observed along the GrIS margins in summer (Turton et al, 2021;Ehrenfeucht et al, 2023;Rawlins et al, 2023), coupled with expected increases in surface melt on the GrIS in a warmer climate (Aschwanden et al, 2019;Muntjewerf et al, 2020), are likely to yield end-of-century discharge estimates at these sites that are comparable to those of Petermann (see projected runoff for the northern, northeastern and northwestern GrIS sectors in Slater et al…”