Using SAR satellite data time series for regional glacier mapping

Winsvold, Solveig H.; Kääb, Andreas; Nuth, C.; Andreassen, Liss M.; Pelt, Ward van; Schellenberger, Thomas

doi:10.5194/tc-12-867-2018

Cited by 61 publications

(41 citation statements)

References 67 publications

(102 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…While the observation distance was much larger in Antarctica (100–1000 km), the occurrence of group 8 icequakes only before the onset of the melt season, the dominance of surface waves, the lack of earlier seismic phases and the location upstream in direction of the firn area may suggest a similar source process at Holtedahlfonna. The timing fits well with lack of melt and rain before the middle of June as well as observations of Winsvold and others (2018), who observed a fast transition from cold and dry conditions in the firn zone to wet-snow conditions above an elevation of 500 m between the middle and the end of June, at the same time as the disappearance of group 8 signals. We, therefore, speculate that static imbalances in the snow and firn may cause sudden settling or fracturing events that emit seismic signals.…”

Section: Discussionsupporting

confidence: 89%

“…This is supported by the absence of diurnal STA/LTA detections before the middle of July during the presence of sufficient snow cover insulating the ice surface (Fig. 2c and Winsvold and others, 2018). However, in case of hydrofracturing, diurnal runoff-related fluctuations would also be dampened by potential refreezing and storage of meltwater in the snow pack.…”

Section: Discussionsupporting

confidence: 57%

“…The recording unit was a 4.5 Hz three-component geophone (SENSOR PE-6/B) connected to a Omnirecs DATA-CUBE data logger operating with a sampling frequency of 100 Hz and using a 12 V, 57 Ah AGM battery as power supply. Station HDF was located in the ablation zone where the ice surface is exposed during summer, at about 10 km distance downstream from the summer snow line (Winsvold and others, 2018). The snow layer was ~2 m thick during installation in April.…”

Section: Data and Study Areamentioning

confidence: 99%

See 2 more Smart Citations

Characterization of seasonal glacial seismicity from a single-station on-ice record at Holtedahlfonna, Svalbard

Köhler

Maupin

Nuth³

et al. 2019

Ann. Glaciol.

Self Cite

View full text Add to dashboard Cite

Glacial seismicity provides important insights into glacier dynamic processes. We study the temporal distribution of cryogenic seismic signals (icequakes) at Holtedahlfonna, Svalbard, between April and August 2016 using a single three-component sensor. We investigate sources of observed icequakes using polarization analysis and waveform modeling. Processes responsible for five icequake categories are suggested, incorporating observations of previous studies into our interpretation. We infer that the most dominant icequake type is generated by surface crevasse opening through hydrofracturing. Secondly, bursts of high-frequency signals are presumably caused by repeated near-surface crevassing due to high strain rates during glacier fast-flow episodes. Furthermore, signals related to resonance in water-filled cracks, fracturing or settling events in dry firn or snow before the melt season, and processes at the glacier bed are observed. Amplitude of seismic background noise is clearly related to glacier runoff. We process ambient seismic noise to invert horizontal-to-vertical spectral ratios for a subsurface seismic velocity model used to model icequake signals. Our study shows that a single seismic sensor provides useful information about seasonal ice dynamics in case deployment of a network is not feasible.

show abstract

Section: Discussionsupporting

confidence: 89%

Section: Discussionsupporting

confidence: 57%

Section: Data and Study Areamentioning

confidence: 99%

See 1 more Smart Citation

Characterization of seasonal glacial seismicity from a single-station on-ice record at Holtedahlfonna, Svalbard

Köhler

Maupin

Nuth³

et al. 2019

Ann. Glaciol.

Self Cite

View full text Add to dashboard Cite

show abstract

“…In most regions of the wet snow zone, the firn has refrozen by the end of August (Figures c and ). However, in aquifer locations, the refreezing of liquid water in the firn is typically delayed due to the insulating effect of autumn snow accumulation, and the substantial amounts of latent heat released upon refreezing (Forster et al, ; Phillips et al, ; Winsvold et al, ). This causes aquifer locations to show a marked delay in the increase of

σ_{HV}^{0}

throughout autumn (Figures c and ).…”

Section: Methodsmentioning

confidence: 99%

Sentinel‐1 Detects Firn Aquifers in the Greenland Ice Sheet

Brangers

Lievens

Miège

et al. 2020

Geophysical Research Letters

View full text Add to dashboard Cite

Firn aquifers in Greenland store liquid water within the upper ice sheet and impact the hydrological system. Their location and area have been estimated with airborne radar sounder surveys (Operation IceBridge, OIB). However, the OIB coverage is limited to narrow flight lines, offering an incomplete view. Here, we show the ability of satellite radar measurements from Sentinel‐1 to map firn aquifers across all of Greenland at 1 km 2 resolution. The detection of aquifers relies on a delay in the freezing of meltwater within the firn above the water table, causing a distinctive pattern in the radar backscatter. The Sentinel‐1 aquifer locations are in very good agreement with those detected along the OIB flight lines (Cohen's κ=0.84). The total aquifer area is estimated at 54,800 km 2. With continuity of Sentinel‐1 ensured until 2030, our study lays a foundation for monitoring the future response of firn aquifers to climate change.

show abstract

“…1; Table 1). Svalbard (e.g., Van Pelt and Kohler, 2015;Vallot et al, 2017;How et al, 2017;Winsvold et al, 2018;Pramanik et al, 2018; 7…”

Section: Validation Datamentioning

confidence: 99%

A long-term dataset of climatic mass balance, snow conditions and runoff in Svalbard (1957–2018)

Pelt¹,

Pohjola²,

Pettersson³

et al. 2019

Preprint

Self Cite

View full text Add to dashboard Cite

Abstract. The climate in Svalbard is undergoing amplified change compared to the global mean. This has major implications for runoff from glaciers and seasonal snow on land. We use a coupled energy balance – subsurface model, forced with downscaled regional climate model fields, and apply it to both glacier-covered and land areas in Svalbard. This generates a long-term (1957–2018) distributed dataset of climatic mass balance (CMB), snow conditions and runoff with a 1x1-km spatial and 3-hourly temporal resolution. Observational data including stake measurements, automatic weather station data and subsurface data across Svalbard are used for model calibration and validation. We find a weakly positive mean CMB (+0.09 m w.e. a−1) over the simulation period, which only fractionally compensates for mass loss through calving. Pronounced warming and a weak precipitation increase lead to a spatial-mean negative CMB trend (−0.06 m w.e. a−1 decade-1), and an increase in the equilibrium line altitude (ELA) by 17 m decade−1, with largest changes in southern and central Svalbard. The retreating ELA in turn causes firn air volume to decrease by 4 % decade−1, which, in combination with winter warming induces a substantial reduction of refreezing in both glacier-covered and land areas (average −4 % decade−1). A combination of increased melt and reduced refreezing cause glacier runoff (average 34.3 Gt a−1) to double over the simulation period, while discharge from land (average 10.6 Gt a−1) remains nearly unchanged. As a result, the relative contribution of land runoff to total runoff drops from 30 to 20 % during 1957–2018. Seasonal snow on land and in glacier ablation zones is found to arrive later in autumn (+1.4 days decade−1), while no significant changes occurred in the date of snow disappearance in spring/summer. Altogether, the output of the simulation provides an extensive dataset that may be of use in a wide range of applications ranging from runoff modelling to ecosystem studies.

show abstract

Using SAR satellite data time series for regional glacier mapping

Cited by 61 publications

References 67 publications

Characterization of seasonal glacial seismicity from a single-station on-ice record at Holtedahlfonna, Svalbard

Characterization of seasonal glacial seismicity from a single-station on-ice record at Holtedahlfonna, Svalbard

Sentinel‐1 Detects Firn Aquifers in the Greenland Ice Sheet

A long-term dataset of climatic mass balance, snow conditions and runoff in Svalbard (1957–2018)

Contact Info

Product

Resources

About