The Non‐Local Impacts of Antarctic Subglacial Runoff

Abstract

Little is known about Antarctic subglacial hydrology, but based on modeling, theory and indirect observations it is thought that subglacial runoff enhances submarine melt locally through buoyancy effects. However, no studies to date have examined effects of runoff on sea ice and oceanography on the continental shelf. Here we use modeled and observational estimates of runoff to force a regional model of the Amundsen Sea Embayment. We find that runoff enhances melt locally (i.e. within the ice‐shelf cavity), increasing melt at Thwaites ice shelf by up to 15 Gt/a given estimates of steady runoff, and up to 25 Gt/a if runoff is episodic as remote sensing measurements suggest. However runoff also has smaller non‐local effects on melt through freshwater influence on flow and stratification. We further find that runoff reduces summer sea‐ice volume over the continental shelf (by up to 10% with steady runoff but over 30% with episodic runoff). Furthermore runoff is much more effective at reducing sea ice than an equivalent volume of ice‐shelf meltwater — due in part to the latent heat loss associated with submarine melting. Results suggest that runoff may play an important role in continental shelf dynamics, despite runoff flux being small relative to ice‐shelf melting — and that runoff‐driven melt and circulation may be an important process missing from regional Antarctic ocean models.

Characterizing Subglacial Hydrology Within the Amery Ice Shelf Catchment Using Numerical Modeling and Satellite Altimetry

“…To investigate this further would require observations of ice velocity and surface elevation change at high spatial and temporal resolution in this area to determine the influence of active lakes on ice dynamics. Importantly, our results demonstrate the influence of concentrated subglacial discharge on the distribution of iceshelf basal melt rates, highlighting that the location and magnitude of subglacial discharge should be considered when simulating ocean melting of ice shelves (e.g., Goldberg et al, 2023;Gwyther et al, 2023) and that temporal variations in subglacial hydrology, due to subglacial lake activity or channel rerouting, could impact ice-shelf basal melting.…”

A Predictive Theory for Heat Transport Into Ice Shelf Cavities

“…The latter assumption holds provided that the cavity is in steady state, that is, over time scales much longer than the cavity flushing time scale (Holland, 2017). Neither assumption takes into account the role of subglacial discharge, which has been shown to be regionally important to basal melt rates (Goldberg et al., 2023; Gwyther et al., 2023). The resulting heat balance can be expressed as $$${\rho }_{\mathrm{i}}{I}_{\mathrm{f}}\,{\dot{m}}WL\sim {\rho }_{0}{C}_{\mathrm{p}}T\left({\theta }_{\text{CDW}}-{\theta }_{\text{surf}}\right)$$$ where W is the cross‐cavity width, $${\dot{m}}$$ is the melt rate per unit area, C p is the specific heat capacity of seawater, ρ 0 is a reference ocean density, ρ i is the reference density of ice, I f is the latent heat of melting, θ CDW is the temperature of the CDW, and θ surf is the surface freezing temperature.…”

Geostrophically Constrained Flow of Warm Subsurface Waters Into Geometrically Complex Ice Shelf Cavities

“…The latter assumption holds provided that the cavity is in steady state, i.e., over time scales much longer than the cavity flushing time scale (Holland, 2017). Neither assumption takes into account the role of subglacial discharge, which has been shown to be regionally important to basal melt rates (Gwyther et al, 2023;Goldberg et al, 2023). The resulting heat balance can be expressed as…”