Salinity evolution and mechanical properties of snow-loaded multiyear sea ice near an ice shelf

Abstract

Sea ice often forms attached to floating ice shelves. Accumulating snow can depress its freeboard, creating a flooded slush layer that may subsequently freeze to form snow ice, rejecting brine as it freezes. The resulting salinity profile determines the mechanical properties of the sea ice. We provide measurements of snow-loaded, multiyear sea ice from summer to winter. Brine from a slush layer is not completely expelled from the sea ice when the slush refreezes to form snow ice. Measurements of sea ice salinity and temperature indicate that the fate of this brine depends on the permeability of the sea ice below it. The sea ice in this study was also deformed by a nearby ice shelf over eleven years at a strain rate _ 5 (-8 ± 3) 3 10 -4 yr -1 (or 3 3 10 -11 s -1). From transects of sea ice thickness and structure we estimate an effective Young's modulus at medium scales for sea ice mostly composed of snow ice of 0.1 GPa , E , 0.4 GPa, suggesting that this eleven year old sea ice cover has similar mechanical properties to warm first year sea ice. This is important for the parameterisations needed to simulate multiyear sea ice in the complex region near an ice shelf.

Observations and modelling of first-year ice growth and simultaneous second-year ice ablation in the Prydz Bay, East Antarctica

“…In March, FYI had a freezing rate of +0.8 cm d −1 , while SYI had a melt rate of −2.7 cm d −1 . A comparable rapid melt rate (2.3 cm d −1 ) of fast ice in March has been observed in other parts of the Antarctic, for example at McMurdo Sound (Gough and others, 2013). The freezing of SYI ice started when the ice thickness was ~0.6 m, in agreement with a modelled theoretical multi-year thermodynamic cycle of minimum ice thickness in Prydz Bay (Yang and others, 2015).…”

Extension of an Ice Shelf Water plume model beneath sea ice with application in McMurdo Sound, Antarctica

“…Relative to a water column at its freezing point, this supercooled water increased sea ice growth by 9 ± 4 cm yr −1 at a distance of 100 km from the ice shelf edge, and by a greater amount closer to the ice shelf. Such increased growth likely contributes to the maintenance of landfast sea ice along the Victoria Land coast (see Figure ), a perennial feature of the region [see Gough et al ., ]. Increased growth is especially evident within kilometers of the ice shelf where we observed that the layer of incorporated platelet ice is more than 1 m thick.…”

“…In recent years, multiyear sea ice persisted and typically formed a band around the southern and western edges of the Sound [see, e.g., Gough et al ., ], with much of the extensive sea ice cover being attributed to the large tabular icebergs in the vicinity of McMurdo Sound during 2000–2005 [ Robinson and Williams , ]. However, in February 2011, an ice breakout left the Sound ice free.…”

Sea ice freeboard in McMurdo Sound, Antarctica, derived by surface-validated ICESat laser altimeter data

“…Surface water is reported as being colder by the end of summer than it had been during noniceberg years [ Robinson and Williams , ]. Not only altering oceanic conditions, the physical barrier created by the icebergs resulted in a limited capacity for expulsion of sea ice from McMurdo Sound [ Remy et al ., ; Gough et al ., ] permitting it to persist. We observed an increase in MY freeboard through the study period together with the large 2005 increase in area.…”

“…At comparison points where the temporal separation is less than 50 days, the mean freeboard retrieval within a radius of 850 m is derived. The repeat pass tracks and crossover points are displayed with the end of summer fast ice edges for each year (Figure ) [ Gough et al ., ]. Values for repeat pass and crossover tracks are displayed as pairs in Figure .…”