Abstract
Abstract. The Nioghalvfjerdsfjorden glacier (also known as the 79∘ North Glacier) drains approximately 8 % of the Greenland Ice Sheet. Supraglacial lakes (SGLs), or surface melt ponds, are a persistent summertime feature and are thought to drain rapidly to the base of the glacier and influence seasonal ice velocity. However, seasonal development and spatial distribution of SGLs in the north-east of Greenland are poorly understood, leaving a substantial error in the estimate of meltwater and its impacts on ice velocity. Using results from an automated detection of melt ponds, atmospheric and surface mass balance modelling, and reanalysis products, we investigate the role of specific climatic conditions in melt onset, extent, and duration from 2016 to 2019. The summers of 2016 and 2019 were characterised by above-average air temperatures, particularly in June, as well as a number of rainfall events, which led to extensive melt ponds to elevations up to 1600 m. Conversely, 2018 was particularly cold, with a large accumulated snowpack, which limited the development of lakes to altitudes less than 800 m. There is evidence of inland expansion and increases in the total area of lakes compared to the early 2000s, as projected by future global warming scenarios.
Highlights
Nioghalvfjerdsfjorden, known as 79◦ North Glacier ( 79◦ N Glacier), is a marine-terminating glacier on the north-eastern coast of Greenland
To summarise the climatic conditions: we find that a combination of above-average air temperatures, a thin presummer snowpack, and summer precipitation falling as rain during summer 2016 and 2019 led to the exposure of a large number of supraglacial lakes (SGLs) over a much larger area than observed in the two other years
We present only 4 years of results here and previous studies in this region are sparse, we are confident that SGLs are a persistent feature in the North East Greenland Ice Stream (NEGIS) and 79◦ N region
Summary
Nioghalvfjerdsfjorden, known as 79◦ North Glacier ( 79◦ N Glacier), is a marine-terminating glacier on the north-eastern coast of Greenland. SGLs influence both the surface mass balance (SMB) and the dynamical stability of glaciers by lowering the albedo at the surface and draining water to the base, which reduces friction and influences ice flow velocity (Zwally et al, 2002; Vijay et al, 2019). Both ice velocity increases and decreases have been linked to the drainage of SGLs across Greenland. Short-lived velocity increases have been observed during summer in several marine-terminating glaciers, including 79◦ N Glacier (Rathmann et al, 2017)
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