Characteristics of the meltwater field from a large Antarctic iceberg using d18O

Large tabular icebergs represent a disruptive influence on a stable water column when drifting in the open ocean. This is a study of one iceberg, C18A, encountered in the Powell Basin in the Weddell Sea in March 2009, formed from iceberg C18 (7637 km) originating from the Ross Ice Shelf in May 2002. C18A was lunate in shape with longest dimensions of 31 km37 km3184 m. The meltwater field from C18A was characterized using dO from water samples collected near C18A (Near-field, 0.4–2 km) and contrasted with a Far-field comprised of samples from an Away site (19 km from C18A), a Control site (70 km away), and a region populated with small icebergs (Iceberg Alley, 175 km away). The in-sample fractions of meteoric water were calculated relative dO in iceberg ice and Weddell Deep Water and converted to meteoric water height (m) and a percentage within 100 m depth bins. The Near-field and Far-field difference from surface to 200 m was 0:5160:28%. The concentration of meteoric water dropped to approximately half that value below 200 m, approximate keel depth of the iceberg, although detectable to 600 m. From surface to 600 m, the overall difference was statistically significant (P < 0:0001). From this, we estimate the Near-field volume astern of the iceberg (0:16 kmd) as a continuous source of meteoric water.