FRIS Revisited in 2018: On the Circulation and Water Masses at the Filchner and Ronne Ice Shelves in the Southern Weddell Sea

Abstract

The Antarctic continent stores the largest amount of freshwater on Earth. However, the Antarctic ice sheets and glaciers are losing mass, leading to a cumulative sea level rise of 14 mm since 1979 (Rignot et al., 2019). Some ice mass loss could be linked to changes in the atmosphere, such as the warming of the Antarctic Peninsula (Vaughan et al., 2003), which triggered the decay of the Larsen ice shelves (Broeke, 2005;Rott et al., 1996). However, the majority of ice mass was lost from glaciers and ice sheets that were exposed to the influence of warm ocean waters (Rignot et al., 2019). Thompson et al. (2018) classify the Antarctic

Ocean Variability Beneath the Filchner‐Ronne Ice Shelf Inferred From Basal Melt Rate Time Series

“…This would be consistent with recent models of the FRIS cavity circulation which also show this circulation pathway (Bull et al, 2021;Hausmann et al, 2020). The year's delay between the sea-ice low and the high melt rates may be related to the time it takes to gather dense water in the Ronne Depression (Janout et al, 2021), but the exact processes by which the HSSW is transported beneath the ice shelf and how those respond to anomalies in the HSSW volume on the continental shelf remain unknown.…”

“…There, Hattermann et al (2021) observed significant inter-annual variations in sub-ice shelf water properties near the Filchner Ice Front, including intermittent intrusions of Berkner HSSW beneath the ice shelf. These dynamics were again related to changes in the circulation strength beneath FRIS that are set by the HSSW forcing originating over the continental shelf north of the Ronne Ice Front (Hattermann et al, 2021;Janout et al, 2021).…”

“…An ISW outflow, located just east of R02, has been observed during summertime ship-based campaigns (Foldvik et al, 1985;Janout et al, 2021). Furthermore, an ice-front mooring FR5 (Figure 1) was deployed in 1995 to monitor the ISW outflow evolution.…”

“…Therefore, it appears unlikely that this secondary inflow would be so pronounced at sites located even further away from the source of the variability. If the two-maxima signal at these sites were caused by multiple pathways, it would require a more refined picture of the FRIS circulation and the currently known two main pathways (Janout et al, 2021) would not be sufficient to explain the data.…”

“…The waters that constitute the Ronne HSSW are formed over the south-western continental shelf and gathered at its deepest bathymetric location, the Ronne Depression (Figure 1). The time elapsed since the last contact with the atmosphere for the densest waters in the depression is five years (Janout et al, 2021). The resulting west-east pressure gradient, set by the water mass distribution along Figure 1.…”