Basal Melting, Roughness and Structural Integrity of Ice Shelves

Abstract

Ice shelves, extensions of glaciers that float over the ocean, act as buttresses restraining the flow of glaciers feeding into them. They restrict outflow from many of the largest glaciers and ice streams in Antarctica. This concept had been considered theoretically for decades, but its reality was very clearly demonstrated by the collapse of the Larsen B Ice Shelf on the east side of the Antarctic Peninsula in 2002 and the subsequent increase in flow velocity of glaciers that had previously flowed into it (De Angelis & Skvarca, 2003;Scambos et al., 2004). Collapse of ice shelves that larger glaciers flow into leading to acceleration of their flow into the ocean would increase the Antarctic contribution to global sea-level rise.Many large glaciers in West Antarctica and some covering large parts of East Antarctica flow on beds that increase in depth upstream. For these glaciers, ice thinning resulting from such flow acceleration would force retreat of their grounding lines, where glacier ice starts to float as it flows toward the ocean. This in turn has the potential to initiate runaway retreat through a feedback process called Marine Ice Sheet Instability (MISI;Schoof, 2007;Weertman, 1974).A further possibility is that sudden ice-shelf collapse could leave tall ice cliffs in which gravitational stress from the mass above water and buoyancy from the submerged part exceeds the yield strength of the ice. Where glacier beds increase in depth upstream, resulting cliff failure would expose even taller cliffs, potentially leading to runaway retreat through a different feedback process called Marine Ice Cliff Instability (MICI; Bassis & Jacobs, 2013;Crawford et al., 2021). There are no examples of MICI having driven substantial retreat during the relatively short period of modern observations of ice-sheet change, but characteristics of iceberg-keel plow marks over an

Reconstructing Continuous Ice Sheet Elevation Changes in the Amundsen Sea Sector During 2003–2021 by Merging Envisat, ICESat, CryoSat‐2, and ICESat‐2 Multi‐Altimeter Observations

“…It is worth noting that the results showed an increasing surface elevation in the zone of Thurston Island, which is contrary to the other margin area of the AS sector. The reason for this is the slope of underlying bedrock and the complex surface topography, so that Thurston Island does not have ice flow channels to the contrary of Pine Island and Thwaites Glaciers (Larter, 2022).…”

Atmospheric Triggers of the Brunt Ice Shelf Calving in February 2021

“…No sea‐ice was present during this period as the event took place in the austral summer season. Although most of the ice loss at the BIS over the last decade has been attributed to the inflow of warm ocean water (Larter, 2022) and to a glaciological cyclic processes (De Rydt et al., 2019), the atmospheric forcing may have played a role in triggering the February 2021 calving event. Therefore, the goal of this paper is to investigate the role of atmospheric conditions together with the state of the ocean and ice in the A‐74 calving event in February 2021.…”

“…Examples include the Amery Ice Shelf in 2019 (Francis et al., 2021), the Larsen C Ice Shelf in 2017 (Hogg & Gudmudsson, 2017), the demise of the Pine Island Glacier (Lhermitte et al., 2020), and the Brunt Ice Shelf (BIS) in February 2021 (Larter, 2022). Most of the studies on ice shelf calving focus on ocean dynamics, targeting aspects such as the role of ocean swells (Massom et al., 2018), the warming and expansion of the Circumpolar Deep Water (Cook et al., 2016; Larter, 2022), the hydrofracturing mechanism and its role in the destabilization of ice shelves (Rott et al., 1996; Scambos et al., 2000, 2003, 2009), and the penetration of Antarctic Surface Water into shelf cavities (Stewart et al., 2019). On top of the ocean and the glaciological factors which precondition ice shelves for calving over long periods of time, the atmospheric forcing may also play a role during the calving events.…”

“…• An intense and stationary cyclone around the ice shelf, which was part of a wave train occurred at the time of the calving • Strong near-surface winds associated with the cyclone promoted the calving of the Brunt Ice Shelf via oceanward sea-surface slope • Calving occurred on 26 February when the ice accelerated significantly in a westward direction from a velocity of 4-6 to 700 m day −1 , the Larsen C Ice Shelf in 2017 (Hogg & Gudmudsson, 2017), the demise of the Pine Island Glacier (Lhermitte et al, 2020), and the Brunt Ice Shelf (BIS) in February 2021 (Larter, 2022). Most of the studies on ice shelf calving focus on ocean dynamics, targeting aspects such as the role of ocean swells (Massom et al, 2018), the warming and expansion of the Circumpolar Deep Water (Cook et al, 2016;Larter, 2022), the hydrofracturing mechanism and its role in the destabilization of ice shelves (Rott et al, 1996;Scambos et al, 2000Scambos et al, , 2003Scambos et al, , 2009, and the penetration of Antarctic Surface Water into shelf cavities (Stewart et al, 2019).…”

The impact of ice base topography, basal channels and subglacial discharge on basal melting --- an exemplary numerical study for the floating ice tongue of the 79◦ North Glacier

“…A growing body of literature recognises the importance of the basal melting of ice shelves in various fields. It is a significant area of interest in glaciology and climate studies since it modifies the buttressing of inland ice, regulates the retreats of outlet glaciers (Walker et al, 2008;Cowton et al, 2018), impacts ice discharge (Miles et al, 2022), influences the structural integrity of ice shelves (Larter, 2022) and indirectly affects sea level rise (Straneo & Heimbach, 2013;Hoffman et al, 2019;Seroussi et al, 2020;Purich, 2022). Basal melting of ice shelves also contributes to glacial meltwater, a classical problem in oceanography.…”