Tidal Modulation of Buoyant Flow and Basal Melt Beneath Petermann Gletscher Ice Shelf, Greenland

摘要: A set of collocated, in situ oceanographic and glaciological measurements from Petermann Gletscher Ice Shelf, Greenland, provides insights into the dynamics under-ice flow driving basal melting. At a site 16 km seaward grounding line within longitudinal channel, two conductivity-temperature (CT) sensors beneath ice base phase-sensitive radar on surface were used to monitor coupled shelf-ocean system. 6 month time series spanning 23 August 2015 12 February 2016 exhibited distinct periods ice-ocean interactions. Between December, radar-derived melt rates featured fortnightly peaks ∼15 m yr-1 which preceded arrival cold fresh pulses ocean that had high concentrations subglacial runoff glacial meltwater. Estimated current speeds reached 0.20 - 0.40 m s-1 during these pulses, consistent with strengthened meltwater plume freshwater enrichment. Such signals did not occur between December February, when interactions instead varied at principal diurnal semidiurnal tidal frequencies, lower prevailed. combination estimated CT yields estimates volume fluxes vary 10 80 m3 s-1 pulses. Area-average upstream shelf are up 170 m yr-1, revealing plumes already driven their most intense melting before arriving study site.