The dynamics of a subglacial salt wedge

Wilson, Earle A.; Wells, Andrew; Hewitt, Ian; Cenedese, Claudia

doi:10.1017/jfm.2020.308

Cited by 13 publications

(46 citation statements)

References 32 publications

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“…1). We will show later that the channelized system of Wilson et al (2020) is a special intermediate case of the generalized theory derived in this study.…”

Section: Hard Bedsmentioning

confidence: 79%

“…microporous), inertial terms become unimportant and the flow of water is better described by Darcy's law, as we discuss further in section 2.2. Wilson et al (2020) originally considered the dynamics of a two-layer shallow water flow for the case of a laterally and vertically confined subglacial channel on an impermeable bed, with free-flowing, fresh subglacial discharge entering a large saltwater body at rest. However, where efficient channelization does not occur, subglacial water flow likely occurs through macroporous sheets (i.e.…”

Section: Hard Bedsmentioning

confidence: 99%

“…not laterally confined) which are kept open by water pressure and the influence of large clasts protruding from the bed (Creyts and Schoof, 2009;Hewitt, 2011). We generalize the seawater intrusion theory of Wilson et al (2020) by considering two-layer macroporous water flow through a vertically confined subglacial sheet over an impermeable bed (illustrated in Fig. 1).…”

Section: Hard Bedsmentioning

confidence: 99%

“…However, the interface between freshwater discharge and seawater can have vertical structure where dense seawater intrudes horizontally under the lighter freshwater forming a "salt wedge", as has been observed in estuaries (Geyer and Ralston, 2011), enclosed wastewater outfalls (Adams et al, 1994), and coastal karst channels (Dermissis, 1993). Wilson et al (2020) first showed in theory and experiments that layered seawater intrusion is possible in laterally-confined subglacial channels (i.e. Rothlisberger or Nye channels), and may extend several kilometers upstream of glacier termini under realistic conditions.…”

Section: Introductionmentioning

confidence: 99%

“…In this study, we generalize the channelized intrusion theory of Wilson et al (2020) to a broader range of subglacial hydrology types which encompass most glacier grounding lines and termini (section 2). This generalized theory predicts that for the wide range of parameters describing subglacial hydrology, seawater intrusion can either be suppressed entirely, or extend 10's of kilometers inland (section 3).…”

Section: Introductionmentioning

confidence: 99%

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Layered seawater intrusion and melt under grounded ice

Robel

Wilson

Seroussi

2021

Preprint

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Abstract. Increasing melt of ice sheets at their floating or vertical interface with the ocean is a major driver of marine ice sheet retreat and sea level rise. However, the extent to which warm, salty seawater may drive melting under the grounded portions of ice sheets is still not well understood. Previous work has explored the possibility that dense seawater intrudes beneath relatively light subglacial freshwater discharge, similar to the salt wedge observed in many estuarine systems. In this study, we develop a generalized theory of layered seawater intrusion under grounded ice, including where subglacial hydrology occurs as a macroporous water sheet over impermeable beds or as microporous Darcy flow through permeable till. Using predictions from this theory, we show that seawater intrusion over hard beds may feasibly occur up to tens of kilometers upstream of a glacier terminus or grounding line. On the other hand, seawater is unlikely to intrude more than tens of meters through subglacial till. High-resolution simulations using the Ice-Sheet and Sea-Level System Model (ISSM) show that even just a few hundred meters of basal melt caused by seawater intrusion upstream of marine ice sheet grounding lines can cause projections of marine ice sheet volume loss to be 10–50 % higher or 100 % higher for kilometers of intrusion-induced basal melt. These results suggest that further observational, experimental and numerical investigations are needed to determine whether the conditions under which extensive seawater intrusion occurs and whether it will indeed drive rapid marine ice sheet retreat and sea level rise in the future.

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“…1). We will show later that the channelized system of Wilson et al (2020) is a special intermediate case of the generalized theory derived in this study.…”

Section: Hard Bedsmentioning

confidence: 79%

Section: Hard Bedsmentioning

confidence: 99%

Section: Hard Bedsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Layered seawater intrusion and melt under grounded ice

Robel

Wilson

Seroussi

2021

Preprint

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Modeling Ice Melt Rates From Seawater Intrusions in the Grounding Zone of Petermann Gletscher, Greenland

Gadi,

Rignot,

Menemenlis

2023

Geophysical Research Letters

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Satellite radar interferometry data reveals that the grounding line of Petermann Glacier, Greenland migrates by several kilometers during the tidal cycle, bringing pressurized, subsurface, warm ocean waters in regular contact with a large sector of grounded ice. We use the Massachusetts Institute of Technology general circulation model in two dimensions to calculate the ice melt rates as a function of grounding zone (GZ) length and ocean Thermal Forcing (TF). Ice melt rates are found to be higher in the GZ cavity than anywhere else in the ice shelf cavity. The melt rates increase sub‐linearly with the length of the GZ and ocean TF. The model results agree well with remote sensing estimates of ice melt. High basal ice melt rates in tidally flushed grounding zones imply that marine‐terminating glaciers are more sensitive to ocean TF than anticipated, which will increase their projected contribution to sea level rise.

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Seawater Intrusion at the Grounding Line of Jakobshavn Isbræ, Greenland, From Terrestrial Radar Interferometry

Kim,

Rignot,

Holland

et al. 2024

Geophysical Research Letters

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Jakobshavn Isbræ, a major outlet glacier in Greenland, lost its protective ice shelf in 2002 and has been speeding up and retreating since. We image its grounding line for the first time with a terrestrial radar interferometer deployed in 2016 and detect its migration at tidal frequencies. The southern half of the glacier develops a floating section (3 km × 3 km) that migrates in phase with the tidal difference, up to a distance of 2.8 km, far more than previously expected. We attribute the migration to kilometer‐scale seawater intrusions, 10–20 cm in height, with the tide. The intrusions reveal that the glacier bed may be up to 800 m deeper than expected on the south side, which illustrates that our knowledge of bed topography remains limited for this glacier. We expect seawater intrusions to cause rapid melt of basal ice and play a major role in the glacier evolution.

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The dynamics of a subglacial salt wedge

Cited by 13 publications

References 32 publications

Layered seawater intrusion and melt under grounded ice

Layered seawater intrusion and melt under grounded ice

Modeling Ice Melt Rates From Seawater Intrusions in the Grounding Zone of Petermann Gletscher, Greenland

Seawater Intrusion at the Grounding Line of Jakobshavn Isbræ, Greenland, From Terrestrial Radar Interferometry

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