Altimetry-based ice-marginal lake water level changes in Greenland: Unveiling annual variations in glacial lake outburst floods linked to runoff

Abstract

Abstract Greenland holds more than 3300 ice-marginal lakes, serving as natural reservoirs for outflow of meltwater to the ocean. A sudden release of water can largely influence ecosystems, landscape morphology, ice dynamics and cause flood hazards. While large-scale studies of glacial lake outburst floods (GLOFs) have been conducted in many glaciated regions, Greenland remains understudied. Here we use altimetry data to provide the first-ever Greenland-wide inventory of ice-marginal lake water level changes, studying over 1100 lakes from 2003–2023, revealing a diverse range of lake behaviors. Around 60% of the lakes exhibit minimal fluctuations, while 326 lakes are actively draining, collectively contributing to 541 observed GLOFs from 2008–2022. These GLOFs vary significantly in magnitude and frequency, with the highest concentration observed in the North and North East regions. Our results show substantial annual differences in the number of GLOFs and the variations are driven by annual difference in meltwater runoff, except for the South West region. Our method detected a 1200% increase in the number of draining lakes compared to existing historical databases. This highlights a significant underreporting of GLOF events and emphasizes the pressing need for a deeper understanding of the mechanisms behind and the consequences of these dramatic events.