Drifting tabular icebergs in the Southern Ocean just east of the Antarctic Peninsula undergo a rapid 'climate change' as they move into warmer air and ocean temperatures. Using a combination of satellite sensors and satellite-uplinked automated observing stations on two bergs during 2006-2007, we examine these changes for clues to ice shelf and ice tongue breakup processes. Icebergs evolve slowly while south of the sea ice edge, but undergo rapid changes as they move north towards South Georgia Island. Surface melt and firn compaction dominate the early evolution (inferred from automated photos of accumulation stakes) but basal melting steadily increases. Edge-wasting of icebergs in warm (sea-ice-free) water suggests a mechanism for ice tongue retreat in the absence of firn saturation and melt ponding. However, in several cases (in situ and satellite-based) we observe rapid calving begins once the firn is saturated with water, and surface or near-surface ponding occurs.