Abstract
Prior to the present study, no dedicated in situ measurement of the thickness distributions of fast ice and the sub-ice platelet layer, formed by supercooled Ice Shelf Water in the near-surface ocean, had been carried out in Terra Nova Bay. Previous studies have recognised the biological importance of the sub-ice platelet layer observed beneath fast ice beside the Campbell Ice Tongue. Furthermore, a recent airborne survey of fast ice in the western Ross Sea implied that smaller ice bodies (ice tongues and outlet glaciers) contribute to the formation of supercooled Ice Shelf Water. With the objective of inferring source regions and circulation of Ice Shelf Water, we measured fast ice and sub-ice platelet layer thickness distributions near the Campbell Ice Tongue in late spring of 2021, using drill hole surveys and high-resolution ground-based electromagnetic induction soundings. We observed thicker fast ice and sub-ice platelet layer near the ice tongue with very thick and narrow sub-ice platelet layer maxima identifying highly channelled outflow of supercooled Ice Shelf Water from beneath the ice tongue through ice mélange, subglacial formations, and grounded regions. We conclude that a significant volume of supercooled Ice Shelf Water is locally sourced from the Campbell Ice Tongue through basal melting and affirm that the icescape in north Terra Nova Bay results from a complex interplay of glacial morphology, bathymetry, polynya dynamics, and ocean circulation.