Greenland Ice Sheet Ice Slab Expansion and Thickening

Jullien, Nicolas; Tedstone, Andrew; Machguth, Horst; Karlsson, Nanna B.; Helm, Veit

doi:10.1002/essoar.10512372.2

Cited by 3 publications

(16 citation statements)

References 28 publications

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“…In contrast, the modeled total aquifer extent increased gradually since the early 2000s and decreased after 2012. Figure S7 and Table S1 in Supporting Information show that recent changes in ice slabs in SW and aquifers in SE agree broadly with observed changes (Horlings et al., 2022; Jullien et al., 2023).…”

Section: Resultssupporting

confidence: 75%

“…Ice‐slab observations for 2010–2018 are taken from Jullien et al. (2023), who used 550–900 MHz airborne accumulation radar from Operation Ice Bridge (OIB) (Carl et al., 2023; CReSIS, 2021). By comparing OIB to in situ measurements from ground penetrating radar, Jullien et al.…”

Section: Methodsmentioning

confidence: 99%

“…By comparing OIB to in situ measurements from ground penetrating radar, Jullien et al. (2023) obtained ice slab probabilities up to a depth of ∼20 m. These probabilities were converted into a binary ice slab extent (see Figures S2 and S3 in Supporting Information for an example).…”

Section: Methodsmentioning

confidence: 99%

“…The model output used in this paper can be found on Zenodo (https://doi.org/10.5281/zenodo.8386406 or https://zenodo.org/records/8386406). OIB data on aquifers (Miège et al., 2016) and ice slabs (Jullien et al., 2023) can be found with their DOIs https://doi.org/10.18739/A2985M (https://arcticdata.io/catalog/view/doi:10.18739/A2985M) and https://doi.org/10.5281/zenodo.7505426 (https://zenodo.org/records/7505426), respectively. The firn‐aquifer extents from Horlings et al (2022) are available through the NSF Arctic Data Center at: https://arcticdata.io/catalog/view/doi:10.18739/A2JM23H40.…”

Section: Data Availability Statementmentioning

confidence: 99%

“…Ice slabs, ice layers of at least 1 m thick, have been detected inside the firn of the western and northern GrIS (Jullien et al., 2023; MacFerrin et al., 2019; Machguth et al., 2016). They limit meltwater storage and facilitate runoff (MacFerrin et al., 2019).…”

Section: Introductionmentioning

confidence: 99%

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Climatic Drivers of Ice Slabs and Firn Aquifers in Greenland

Brils,

Munneke,

Jullien

et al. 2024

Geophysical Research Letters

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Recent observations revealed the existence of ice slabs and aquifers on the Greenland ice sheet (GrIS). Both affect the ice sheet's hydrology: ice slabs facilitate runoff and aquifers modulate drainage to the bed. However, their climatic drivers and history remain unclear, as most observations cover only two decades. Here, we present a model simulation of the evolution of GrIS ice slabs and aquifers (1980–2020), evaluated using radar measurements. The results show that accumulation, melt and rain rates are good predictors for the spatial distribution of ice slabs and aquifers. Both features were already present in the late 1980s, and their extent remained relatively constant until the beginning of this century, after which increased melt led to their expansion. We show that almost any transect from the coast to the ice‐sheet interior will cross either an ice slab region, or an aquifer, or both.

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Section: Resultssupporting

confidence: 75%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Data Availability Statementmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Climatic Drivers of Ice Slabs and Firn Aquifers in Greenland

Brils,

Munneke,

Jullien

et al. 2024

Geophysical Research Letters

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Mapping the vertical heterogeneity of Greenland's firn from 2011–2019 using airborne radar and laser altimetry

Rutishauser,

Scanlan,

Vandecrux

et al. 2024

The Cryosphere

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Abstract. The firn layer on the Greenland Ice Sheet (GrIS) plays a crucial role in buffering surface meltwater runoff, which is constrained by the available firn pore space and impermeable ice layers that limit deeper meltwater percolation. Understanding these firn properties is essential for predicting current and future meltwater runoff and its contribution to global sea-level rise. While very-high-frequency (VHF) radars have been extensively used for surveying the GrIS, their lower bandwidth restricts direct firn stratigraphy extraction. In this study, we use concurrent VHF airborne radar and laser altimetry data collected as part of Operation IceBridge over the 2011–2019 period to investigate our hypothesis that vertical heterogeneities in firn (i.e. ice layers) cause vertical offsets in the radar surface reflection (dz). Our results, corroborated by modelling and firn core analyses, show that a dz larger than 1 m is strongly related to the vertical heterogeneity of a firn profile and effectively delineates between vertically homogeneous and vertically heterogeneous firn profiles over a depth range of ∼ 4 m. Temporal variations in dz align with climatic events and reveal an expansion of heterogeneous firn between 2011–2013 covering an area of ∼ 350 815 km2, followed by firn replenishment over the years 2014–2019 spanning an area of ∼ 667 725 km2. Our approach reveals the firn evolution of key regions on the Greenland Ice Sheet, providing valuable insights for detecting potential alterations in meltwater runoff patterns.

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Sentinel-1 detection of ice slabs on the Greenland Ice Sheet

Culberg,

Michaelides,

Miller

2024

The Cryosphere

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Abstract. Ice slabs are multi-meter-thick layers of refrozen ice that limit meltwater storage in firn, leading to enhanced surface runoff and ice sheet mass loss. To date, ice slabs have primarily been mapped using airborne ice-penetrating radar, which has limited spatial and temporal coverage. This makes it difficult to fully assess the current extent and continuity of ice slabs or to validate predictive models of ice slab evolution that are key to understanding their impact on Greenland's surface mass balance. Here, for the first time, we map the extent of ice slabs and superimposed ice facies across the entire Greenland Ice Sheet at 500 m resolution using dual-polarization Sentinel-1 (S-1) synthetic-aperture radar (SAR) data collected in winter 2016–2017. We do this by selecting empirical thresholds for the cross-polarized backscatter ratio and HV backscattered power that jointly optimize the agreement between airborne ice-penetrating radar data detections of ice slabs and the S-1 estimates of ice slab extent. Our results show that there is a strong correlation between C-band backscatter and the ice content of the upper ∼ 7 m of the firn column that enables ice slab mapping with S-1. Our new mapping shows that ice slabs are nearly continuous around the entire margin of the ice sheet. This includes regions in southwest Greenland where ice slabs have not been previously identified by ice-penetrating radar but where the S-1-inferred ice slab extent shows strong agreement with the extent of visible runoff mapped from optical imagery. The algorithm developed here lays the groundwork for the long-term monitoring of ice slab expansion with current and future C-band satellite systems and highlights the potential added value of future L-band missions for near-surface studies in Greenland.

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Greenland Ice Sheet Ice Slab Expansion and Thickening

Cited by 3 publications

References 28 publications

Climatic Drivers of Ice Slabs and Firn Aquifers in Greenland

Climatic Drivers of Ice Slabs and Firn Aquifers in Greenland

Mapping the vertical heterogeneity of Greenland's firn from 2011–2019 using airborne radar and laser altimetry

Sentinel-1 detection of ice slabs on the Greenland Ice Sheet

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