Spatiotemporal Changes of Supraglacial Hydrology on Ellesmere Island in Response to Increases in Surface Melt

Abstract

Over the past two decades, the Canadian Arctic Archipelago (CAA) has experienced unprecedented glacier mass loss, with surface melt and runoff contributing 90% of this decline since 2005. This has led to the formation and expansion of supraglacial streams and river networks. This study employs remotely sensed optical satellite imagery, historical air photographs, and digital elevation models (DEMs) to provide the first comprehensive spatiotemporal assessment of supraglacial drainage patterns on Ellesmere Island between 1959 and 2020. Through multi-decadal qualitative and quantitative analyses of five glaciers along the ~830 km latitudinal gradient of Ellesmere Island, consistent drainage patterns influenced by surface topography were observed, which affects channelization and sinuosity. Substantial increases in drainage density from 1959 to 2020 were driven by the expansion of perennial incised and canyon rivers, especially at higher elevations. This shift is observed through a reorganization of channel types towards a more perennial system, with incised rivers becoming predominant and canyons contributing more to the total channel length. Notably, Unnamed 1 Glacier on far northern Ellesmere Island has shown increased channelization of its perennial system and a trend towards straighter channels, while Unnamed 2 and John Evans glaciers to the south have experienced more pronounced canyon development in their lower ablation areas. The presence of cold ice near the surface on Unnamed 1 Glacier, evidenced by limited sinks and numerous incised channels, results in high drainage density dominated by canyon and incised rivers. Similarly, Henrietta-Nesmith Glacier's low moulin count and high canyon drainage density suggest a comparable cold ice pattern. In contrast, southern glaciers with extensive moulin fields, such as Unnamed 2 and John Evans Glacier, show better supraglacial-subglacial connectivity, affecting the development of the subglacial system and glacier dynamics. The limited change in sinuosity, combined with channel dynamism, indicates varied stages of canyon evolution influenced by hydraulic factors such as surface slope and watershed area. These findings align with modeled increases in surface melt, with southern glaciers experiencing higher melt production and rapid expansion of their supraglacial systems, while northern glaciers like Unnamed 1 show relative stability in part due to lower melt rates. In contrast, greater cumulative summer losses on Sydkap combined with extensive crevassing limit the development of a perennial supraglacial system. Future climate warming is expected to raise the Equilibrium Line Altitude (ELA) and enhance melt rates at higher elevations, particularly impacting glaciers with a substantial amount of ice at mid-elevations, such as Unnamed 2. Although glaciers like Unnamed 1 may continue to expand their supraglacial systems, especially at higher elevations, this glacier’s overall retreat suggests a future potential for complete glacier loss.