Quantifying vulnerability of Antarctic ice shelves to hydrofracture using microwave scattering properties

Alley, Karen E.; Scambos, Ted; Miller, Julianne J.; Long, D.G.; MacFerrin, Michael

doi:10.1016/j.rse.2018.03.025

Cited by 56 publications

(87 citation statements)

References 35 publications

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“…Therefore, enhanced melt events during these shoulder seasons have the potential to affect the percolation of liquid water into deeper layers and leave a lasting impact on the firn layer, even if meltwater production in the summer continues to decrease in the future. Previous work has proposed that ice shelf stability can be estimated from firn‐ice concentration (Alley et al, ) or firn air content (Holland et al, ), presuming a seasonal cycle with firn air depletion during the summer balanced by winter snowfall. Even occasional late‐season melt events may therefore disproportionately affect the capacity of firn to retain liquid water and therefore ice sheet stability.…”

Section: Discussionmentioning

confidence: 99%

The Effect of Foehn‐Induced Surface Melt on Firn Evolution Over the Northeast Antarctic Peninsula

Datta

Tedesco

Fettweis

et al. 2019

Geophysical Research Letters

126

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Surface meltwater ponding has been implicated as a major driver for recent ice shelf collapse as well as the speedup of tributary glaciers in the northeast Antarctic Peninsula. Surface melt on the NAP is impacted by the strength and frequency of westerly winds, which result in sporadic foehn flow. We estimate changes in the frequency of foehn flow and the associated impact on snow melt, density, and the percolation depth of meltwater over the period 1982–2017 using a regional climate model and passive microwave data. The first of two methods extracts spatial patterns of melt occurrence using empirical orthogonal function analysis. The second method applies the Foehn Index, introduced here to capture foehn occurrence over the full study domain. Both methods show substantial foehn‐induced melt late in the melt season since 2015, resulting in compounded densification of the near‐surface snow, with potential implications for future ice shelf stability.

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Section: Discussionmentioning

confidence: 99%

The Effect of Foehn‐Induced Surface Melt on Firn Evolution Over the Northeast Antarctic Peninsula

Datta

Tedesco

Fettweis

et al. 2019

Geophysical Research Letters

126

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“…The spectral albedo of liquid meltwater (*0.4-0.6) is approximately half of snowcovered ice (Figure 2) (Box and Ski, 2007;Tedesco, 2014), which leads to a positive feedback, whereby the lower albedo of the SGLs enhances melting and can lead to further increase in lake area and depth (Banwell et al, 2015;Morriss et al, 2013;Tedesco et al, 2012). For meltwater to pond in SGLs in areas of firn cover, percolation into the near-surface firn layer must be impeded by firn over-saturation or refrozen englacial meltwater (Alley et al, 2018;Harper et al, 2012;Hubbard et al, 2016;Lenaerts et al, 2017;Reynolds and Smith, 1981).…”

Section: Controls On Supraglacial Lake Formation In Antarcticamentioning

confidence: 99%

“…In particular, larger lakes that migrate towards the front of the Larsen C Ice Shelf under warmer atmospheric conditions may deepen sufficiently to remain unfrozen between melt seasons, thereby pre-disposing them for hydrofracture (Buzzard et al, 2018b). The depleted firn air thickness of Larsen C (0.3m in western inlets) also increases the likelihood of extensive SGL ponding and future instability, driven by sustained föhn-enhanced melting (Alley et al, 2018;Holland et al, 2011). The presence of a massive, dense ice lens in Cabinet Inlet confirms an ice-saturated firn layer conducive to SGL ponding (Hubbard et al, 2016).…”

Section: Antarctic Peninsulamentioning

confidence: 99%

“…Surface melt fluxes are derived from QuickScat scatterometer (2000( average, Trusel et al, 2013 and include meltwater that could refreeze in the snow/firn. Ice shelf vulnerability is derived from QuikSCAT data and represents the relative concentration of refrozen meltwater in the firn (Alley et al, 2018). The grounding line and coastline are represented by dotted and solid black lines respectively.…”

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confidence: 99%

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Recent understanding of Antarctic supraglacial lakes using satellite remote sensing

Arthur

Stokes

Jamieson

et al. 2020

Progress in Physical Geography: Earth and Environment

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Supraglacial lakes (SGLs) are now known to be widespread in Antarctica, where they represent an important component of ice sheet mass balance. This paper reviews how recent progress in satellite remote sensing has substantially advanced our understanding of SGLs in Antarctica, including their characteristics, geographic distribution and impacts on ice sheet dynamics. Important advances include: (a) the capability to resolve lakes at sub-metre resolution at weekly timescales; (b) the measurement of lake depth and volume changes at seasonal timescales, including sporadic observations of lake drainage events and (c) the integration of multiple optical satellite datasets to obtain continent-wide observations of lake distributions. Despite recent progress, however, there remain important gaps in our understanding, most notably: (a) the relationship between seasonal variability in SGL development and near-surface climate; (b) the prevalence and impact of SGL drainage events on both grounded and floating ice and (c) the sensitivity of individual ice shelves to lake-induced hydrofracture. Given that surface melting and SGL development is predicted to play an increasingly important role in the surface mass balance of Antarctica, bridging these gaps will help constrain predictions of future rapid ice loss from Antarctica.

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“…In these inlets, most notably in Cabinet Inlet, repeated years of melt/refreeze cycles have left the ice shelf surface sufficiently impermeable to support ponds of surface melt water (Alley et al, 2018;Kuipers Munneke et al, 2014;Scambos et al, 2000), a phenomenon which preceded, and may have led to, the collapse of Larsen A, Larsen B, and Wilkins Ice Shelves (Sergienko & Macayeal, 2005;van den Broeke, 2005). Although melt ponds have been observed on LCIS, they are confined to the western inlets where they occupy shallow surface troughs originating at the grounding line (Hubbard et al, 2016;Luckman et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Decline in Surface Melt Duration on Larsen C Ice Shelf Revealed by The Advanced Scatterometer (ASCAT)

Bevan

Luckman

Munneke

et al. 2018

Earth and Space Science

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Surface melting has been contributing to the surface lowering and loss of firn air content on Larsen C Ice Shelf since at least the mid‐1990s. Where the amount of melting and refreezing is significant, the firn can become impermeable and begin to support ponds of surface meltwater such as have been implicated in ice shelf collapse. Although meteorological station data indicated an increase in melt on the Antarctic Peninsula over the second half of the 20th century, the existing Ku‐band Quick Scatterometer (QuikSCAT) time series is too short (1999–2009) to detect any significant 21st century trends. Here we investigate a longer 21st century period by extending the time series to 2017 using the C‐band Advanced Scatterometer (ASCAT). We validate our recent observations with in situ weather station data and, using a firn percolation model, explore the sensitivity of scatterometry to water at varying depths in the firn. We find that active microwave C‐band (5.6‐cm wavelength) instruments can detect water at depths of up to 0.75 m below a frozen firn layer. Our longer scatterometry time series reveals that Larsen C Ice Shelf has experienced a decrease in melt season length of 1–2 days per year over the past 18 years consistent with decreasing summer air temperatures. Only in western inlets, where föhn winds drive melt, has the annual melt duration increased during this period.

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Quantifying vulnerability of Antarctic ice shelves to hydrofracture using microwave scattering properties

Cited by 56 publications

References 35 publications

The Effect of Foehn‐Induced Surface Melt on Firn Evolution Over the Northeast Antarctic Peninsula

The Effect of Foehn‐Induced Surface Melt on Firn Evolution Over the Northeast Antarctic Peninsula

Recent understanding of Antarctic supraglacial lakes using satellite remote sensing

Decline in Surface Melt Duration on Larsen C Ice Shelf Revealed by The Advanced Scatterometer (ASCAT)

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