Abstract
Intermittent calving of tidewater Maar Glacier into Arthur Harbor (Anvers Island, Antarctic Peninsula) produces mainly brash ice (fragments < 2 m in diameter). To assess the potential role of brash ice in the seaward transport of glacigenic sediment in this subpolar region, measurements were made of (1) brash melt rates under laboratory and field conditions and (2) size distributions of freshly calved brash. In constant-temperature (1 °C) laboratory runs, melt rates for similarly shaped bergs increased significantly with relative flow velocity and were also greater for bergs containing fractures or air bubbles. Under field conditions, brash bergs subjected to rough open water were observed to melt approximately 20 times faster (range = 12–26) than those locked in densely packed jams protected from wave and current action. Published melt-rate equations developed for deep-draft or still-water bergs greatly underestimate melt rates for brash in rough sea surfaces. Size-frequency distributions (by weight) of four 102 m
2 samples of dense brash are closely approximated by Rosin-probability distributions. For an average population of freshly calved brash subjected to mean open-water melt rates observed in Arthur Harbor, over 90% of the bergs will completely melt within 24 hours. Consequently, little brash escapes the proximal marine zone, and most debris rafted by such bergs is probably deposited within a few hundred meters of the glacier terminus.