Crevasse refreezing and signatures of retreat observed at Kamb Ice Stream grounding zone

Abstract

Ice streams flowing into Ross Ice Shelf are presently responsible for around 10% of the mass flux from West Antarctica, with the noteworthy exception of Kamb Ice Stream, which stagnated in the late 1800s. The subsequent reduction in ice supply led to grounding-line retreat at the coastal margin where Kamb transitions into the floating Ross Ice Shelf. Grounding-line migration is linked to broader changes in ice-sheet mass balance and sea level, but our understanding of related ice, ocean and seafloor interactions is limited by the difficulty in accessing these remote regions. Here we report in situ observations from an underwater vehicle deployed at Kamb that show how fine-scale variability in ice and ocean structure combine to influence a diversity of ice–ocean interactions. We found a stratified water column within a tenth of a degree of freezing at the ice base and mapped basal crevasses with supercooled water and active marine ice formation. At the seafloor, we interpret parallel ridges as crevasse impressions left as the ice lifted off during grounding-line retreat. These observations from a recently ungrounded sub-shelf environment illuminate both the geomorphological signatures of past grounding-line retreat and the fine-scale sensitivity of ongoing ice–ocean interactions to ice topography.

Double‐Diffusive Layer and Meltwater Plume Effects on Ice Face Scalloping in Phase‐Change Simulations

“…taking measurements in the extreme Antarctic environment (Begeman et al, 2018;Davis et al, 2023;Lawrence et al, 2023;Noble et al, 2020;Schmidt et al, 2023).…”

Direct observations of melting, freezing, and ocean circulation in an ice shelf basal crevasse

“…1). They are an extension of those discussed in (20), which described ice, ocean, and seafloor properties over the full region surveyed with Icefin. This survey was made possible by deploying Icefin through a borehole drilled with hot water.…”

“…Throughout the text, we refer to the region spanning from the furthest tidally affected inland GL location to the point of full hydrostatic flotation as the grounding zone (GZ). To date, published oceanographic measurements exist in less than 10 Antarctic GZ ocean cavities (19)(20)(21)(22)(23)(24)(25). This leaves much uncertainty about the hydrographic properties, circulation patterns, and dominant scales of variability that drive ice-ocean interactions in these regions around Antarctica.…”

“…It is estimated that pervasive rifting leading to iceberg calving removes the majority of mass from the Filchner-Ronne, Ross, and Amery ice shelves ( 30 ), Antarctica’s three largest ice shelves that constitute 63% of the total ice shelf area ( 1 ). There are only four published studies that present in situ ocean measurements from within a crevasse or rift ( 20 , 31 – 33 ), none of which discuss three-dimensional circulation and detailed melt and freeze rates throughout the feature. This results in large uncertainty about the ocean’s role in crevasse evolution and ice shelf stability and how crevasses in turn influence ocean cavity circulation.…”

Geometry of Freezing Impacts Ice Composition: Implications for Icy Satellites

“…While we do not explicitly model free floating crystal formation in our ice-brine system simulations, a common process observed in both magmatic and metallurgic analog systems (e.g., Figure 9b), we do observe freshwater melt plumes pooling at the fracture tips during some model runs (e.g., Movie S13). Such buoyantly rising masses of freshwater have the potential to form frazil/platelet ice crystals via the ice pump mechanism (depressurization crystallization)-potentially infilling fractures with an inverted snowfall of ice crystals (akin to marine/frazil ice accretion on Earth (Craven et al, 2009;Fricker et al, 2001;Galton-Fenzi et al, 2012;Holland et al, 2009;Khazendar & Jenkins, 2003;Khazendar et al, 2009;Lawrence et al, 2020;McGuinness et al, 2009;Smedsrud & Jenkins, 2004)) and leading to an analogous region of segregation (in this case exceptionally fresh ice (Wolfenbarger et al, 2018(Wolfenbarger et al, , 2019) at the fracture tip. SOFTBALL does not currently account for the pressure-dependent freezing point depression of the ocean.…”