Photographs showing dispersal of tracer (ca. 5 g Fluoresceine) on day 198 in a ridged area ("Ridge" mass balance site visible in background in upper left panel; local hydraulic gradients on the order of 0.01 to 0.1) 25, 40 and 110 min. after release. A significant portion of the flow is confined to the highly permeable uppermost ice layer (see lowermost right of core taken at point shown in upper right panel - note that two tracer plumes are result of confluence of two separate tracer releases). Temperature measurements demonstrate heating of water in ponds to >0.3ūC and differential cooling in narrow channels and subsurface flow. Meltwater from a large fraction of the ridge flank drained into puddle visible in foreground (lower left panel) which was in hydraulic connection with the sea.

Discharge of meltwater through natural (at site Atlanta) and artificial holes (at site Sed City). Discharge and extent of drainage basin were determined through release of tracers at different loca-tions within the basin and at the drainage site. After day 195 large-scale drainage essentially came to a stop (see also sketch of seasonal evolution).       Based on the drainage basin size (approximately 500 to 1500 m2), average basin-wide ablation rates have been derived. Meltwater discharge was mostly confined to thermal cracks that had corroded all the way through the ice cover, typically draining areas on the order of several hundreds to thousands of m2). During the first half of the melt season, freshwater discharge was associated with vigorous under-water ice formation.