During summer 1988, a large area of reduced ice concentration developed within the Arctic pack ice of the Canada Basin. Data from the special sensor microwave imager (SSM/I) and visible-band imagery show that by early September, this feature extended north of 80¿N, with SSM/I-derived ice concentrations of 40-80% covering an area approximately 1.0¿106 km2. Drifting buoys, surface pressure fields, output from the Polar Ice Prediction System (PIPS) sea ice model and other meteorological data are used to examine processes responsible for development of the reduced ice concentrations. While the model indicates that ice divergence in summer offers a partial explanation, (1) anomalously warm atmospheric conditions, (2) geneally clear skies in June and July, (3) extensive fracturing of the pack ice in spring and, perhaps, (4) anomalous advection of oceanic heat may all have played contributing roles. However, the second and third of these effects may occur in most years. Coupled with additional observations suggestive of recurring bathymetrically induced effects on lateral transport of ocean heat, we conclude that although the extent and magnitude of the concentration reductions during 1988 are unusual, these recurring factors tend to predispose the pack ice in the Canada Basin to decay. ¿ American Geophysical Union 1990