The influence of an Antarctic ice shelf on land-fast sea ice detected by in-situ and satellite measurements.
In proximity to ice shelves, the growth of land-fast sea ice can be influenced by meltwater in the upper surface ocean originating from basal melting. In the western Ross Sea, strong southerly winds advect sea ice offshore and form regions of open water called coastal polynyas. Sea ice is produced i...
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| Format: | Other/Unknown Material |
| Language: | English |
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University of Canterbury
2020
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| Online Access: | https://hdl.handle.net/10092/100740 https://doi.org/10.26021/940 |
| Summary: | In proximity to ice shelves, the growth of land-fast sea ice can be influenced by meltwater in the upper surface ocean originating from basal melting. In the western Ross Sea, strong southerly winds advect sea ice offshore and form regions of open water called coastal polynyas. Sea ice is produced intensively within polynyas and the rejected brine forms highly dense and saline High Salinity Shelf Water which can sink down into a nearby ice shelf cavity and melt or dissolve the ice shelf base at depth. The meltwater has a potential temperature below the surface freezing point and forms buoyant plumes of Ice Shelf Water which rise along the basal slope becoming in-situ supercooled as the pressure decreases. Supercooling promotes the formation of frazil ice which can grow into larger platelet ice crystals. The outflow of supercooled Ice Shelf Water from the McMurdo-Ross Ice Shelf cavity drives accelerated land-fast sea ice formation, increased sea ice thicknesses, and the formation of an unconsolidated sub-ice platelet layer in McMurdo Sound. The volume of supercooled Ice Shelf Water outflowing into McMurdo Sound is reflected in the thickness of ice shelf-influenced land-fast sea ice and the sub-ice platelet layer beneath. In this thesis, spatio-temporal variability in the distribution of land-fast sea ice and the sub-ice platelet layer was assessed in McMurdo Sound using a combination of drill hole and electromagnetic induction surveying and satellite altimetry techniques. A consistent pattern of thicker ice shelf- influenced land-fast sea ice with a substantial sub-ice platelet layer beneath was observed in the central-western region of the sound. On interannual timescales, thicker and variable sub-ice platelet layers were observed in late spring following winters subject to a higher occurrence of strong southerly wind events and resultant polynya activity. It was hypothesized from this study that a higher frequency of polynya activity over winter and resultant High Salinity Shelf Water production accelerates ... |
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