In September 1997, the CCGS Des Groseillers was frozen into the permanent ice-pack and started a year-long science program drifting across the southern Canada Basin. This program provided a unique opportunity to carry out a "vertical" food-chain study in a seasonal context to learn how the physical and biological systems couple to produce contaminant entry into the food web (Figure 1). "Vertical" components included the water and ice, particles, algae, zooplankton (sorted by trophic level), fish and seal.. The interpretation of contaminant data collected during SHEBA will provide information about the relationship between seasonal ice formation and melt, seasonal atmospheric transport and water column organochlorine concentrations in the Canada Basin. In addition our contaminant sampling program was integrated within a larger science plan where other SHEBA researchers studied the physical and biological properties of the water column. This means that contaminant distributions can be interpreted and modeled within the full context of physical, chemical and biological processes, and of atmospheric and oceanic transport mechanisms.