Daily variations in Western Greenland slush limits, 2000–2021

Machguth, Horst; Tedstone, Andrew; Mattea, Enrico

doi:10.1017/jog.2022.65

Cited by 7 publications

(5 citation statements)

References 46 publications

(84 reference statements)

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“…The evolution of slush limit altitude throughout the melt season has been investigated based on remote sensing data and by degree-day modelling (Greuell and Knap, 2000;Machguth et al, 2022), but since in situ measurements made at the runoff limit do not exist as of yet, it is challenging to determine what governs the distance between the slush and runoff limit. Even though we have quantified vertical and lateral meltwater flow velocities through snow and firn near the runoff limit in this paper, we lack other essential data to further constrain and describe the hydrological system in the accumulation area of the SW Greenland Ice Sheet.…”

Section: The Slush Vs the Runoff Limitmentioning

confidence: 99%

In situ measurements of meltwater flow through snow and firn in the accumulation zone of the SW Greenland Ice Sheet

et al. 2022

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Abstract. The Greenland Ice Sheet is losing mass, part of which is caused by increasing runoff. The location of the runoff limit, the highest elevation from which meltwater finds its way off the ice sheet, plays an important role in the surface mass balance of the ice sheet. The recently observed rise in runoff area might be related to an increasing amount of refreezing: ice layer development in the firn reduces vertical percolation and promotes lateral runoff. To investigate meltwater flow near the runoff limit in the accumulation zone on the southwestern Greenland Ice Sheet, we carried out in situ measurements of hydrological processes and properties of firn and snow. The hydraulic conductivity of icy firn in pre-melt conditions measured using a portable lysimeter ranges from 0.17 to 12.8 m h−1, with flow predominantly occurring through preferential flow fingers. Lateral flow velocities of meltwater on top of the near-surface ice slab, measured at the peak of the melt season by salt dilution and tracer experiments, range from 1.3 to 15.1 m h−1. With these lateral flow velocities, the distance between the slush limit, the highest elevation where liquid water is visible on the ice sheet surface, and the runoff limit could be roughly 4 km in regions where near-surface ice slabs are present. These measurements are a first step towards an integrated set of hydrological properties of firn on the SW Greenland Ice Sheet and show evidence that meltwater runoff may occur from elevations above the visible runoff area.

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Section: The Slush Vs the Runoff Limitmentioning

confidence: 99%

In situ measurements of meltwater flow through snow and firn in the accumulation zone of the SW Greenland Ice Sheet

et al. 2022

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“…The surveyed sites are located more than 100km from the front of Jakobshavn Isbrae, north of the main ice stream. This area is in the low accumulation, percolation zone [14] see figure 1, and above the melt-water runoff limit [38]. While basal sliding and sediment deformation may be occurring beneath our survey sites, we interpret the continued absence of an active supraglacial hydrology system to suggest there has been no recent change in basal hydrology associated with basal sliding and sediment deformation.…”

Section: Increasing Velocitymentioning

confidence: 78%

Recent ice-flow acceleration and rotation in the Greenland Ice Sheet interior

Løkkegaard

Colgan²,

Thorsøe³

et al. 2023

Preprint

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In the past two decades, mass loss from the Greenland ice sheet has accelerated, partly due to speedup of glaciers. However, uncertainty in speed derived from satellite products hampers detection of inland changes. In-situ measurements using stake surveys or GPS have lower uncertainties. To detect inland changes, we repeated in-situ measurements of ice-sheet surface velocities at historical locations first measured in 1959. Here, we show ice velocities have increased 5-15% across all deep inland sites. Several sites show a northward deflection of 3-4.5° in their flow azimuth. The recent appearance of a network of large transverse surface crevasses, bisecting historical overland traverse routes, may suggest a fundamental shift in local ice dynamics. We suggest that creep instability - a coincident warming and softening of near-bed ice layers - may explain recent acceleration and rotation, in the absence of a change in local driving stress. This mechanism, if included in simulations may improve projections of future ice loss.

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“…Thirdly, slush and SI form, particularly in the spring when the snow melts due to increased solar radiation or precipitation (Machguth and others, 2023) and the meltwater subsequently refreezes to SI known as superimposed ice (Nicolaus and others, 2003; Granskog and others, 2006). The SI formation due to melting has been observed to change the surface albedo and delay the melting of ice (Perovich and others, 1998).…”

Section: Introductionmentioning

confidence: 99%

Initial snow-ice formation on a laboratory scale

et al. 2023

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Snow ice (SI) forms from freezing wet snow, known as slush, and contributes to the thickness of level and brash ice. However, the mechanism of snow-slush-snow ice transformation has not been extensively investigated to date, despite the difference in the freezing rate of slush in comparison with water is important for estimating the ice thickness. In this study, we examined the growth of initial congelation ice (CI) and snow ice (SI) in a fresh water tank exposed to outdoor weather conditions in Luleå, northern Sweden. The tank of size 1.8 × 0.65 × 1.2 m in length, width and height was divided into two compartments to facilitate the simultaneous growth of CI and SI. A total of 12 experiments were conducted in the years 2021 and 2022. The transformation from slush to snow ice was achieved by submerging various amounts of snow in the compartments. It was observed that approximately 35% of the initial snow transformed into SI. Snow ice grew 4 mm°C−0.5 d−0.5 faster than congelation ice. The CI growth under SI was 1 mm°C−0.5 d−0.5 slower than the CI growth under CI. This study provides valuable insights for modelling snow-slush-snow ice transformation and designing future laboratory-scale experiments.

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Daily variations in Western Greenland slush limits, 2000–2021

Cited by 7 publications

References 46 publications

In situ measurements of meltwater flow through snow and firn in the accumulation zone of the SW Greenland Ice Sheet

In situ measurements of meltwater flow through snow and firn in the accumulation zone of the SW Greenland Ice Sheet

Recent ice-flow acceleration and rotation in the Greenland Ice Sheet interior

Initial snow-ice formation on a laboratory scale

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