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Arctic landfast sea ice is widely utilized for transportation by local communities and industry, with trafficability largely governed by ice roughness. Here, we introduce an approach to evaluate ice roughness that can aid in routing of ice roads and assessment of spatial variability and long-term changes in trafficability. Drawing on synthetic aperture radar (SAR) polarimetry, SAR interferometry (InSAR), and other remote sensing techniques, we integrated approaches into the trafficability assessment that had rarely been applied over sea ice in the past. Analysis of aerial photogrammetry obtained through structure-from-motion helped verify cm-scale accuracy of X-band InSAR-derived ridge height and link L-band polarimetric classification to specific roughness regimes. Jointly, these approaches enable a km-scale evaluation of ridge topography and cm- to m-scale roughness—both critical for the assessment of trafficability. A trafficability index was derived from such SAR data in conjunction with analysis of ice trail routing and ice use near Utqiaġvik, Alaska. The index identifies areas of reduced trafficability, associated with pressure ridges or rubble ice, and served to delineate favorable trail routes for different modes of transportation, with potential uses ranging from ice road routing to emergency evacuation. Community outreach is needed to explore how this approach could assist different ice users in reducing risk, minimizing trail or ice construction efforts, and improving safety.

At Barrow, Alaska, local Inupiat whaling crews annually construct a network of seasonal trails through the shorefast ice during the traditional spring hunting season. These trails originate at locations along the coast and pass through diverse ice features, including ridged and rubbled ice, new and potentially flooded ice, and tidal cracks, before terminating at the shorefast ice edge where camps are established. The safety of this hunt relies on the careful observation of evolving ice characteristics from freeze-up onward and the understanding of how the interplay between ice dynamics, ice thermal evolution, and ocean and atmospheric processes leads to both stable and dangerous conditions. Partnering with Barrow whalers, a multi-year documentation of whaling trails, alongside a geophysical record of shorefast ice conditions, provides insight into how Inupiat hunters monitor the development of the shorefast ice throughout winter and spring and how individual and community assessments of ice conditions and associated risks, traditions and knowledge, and personal preference determine trail placement. This contribution also discusses how the documentation of human use of the ice environment contributes to integrated observations of Arctic change and adaptation.

Although shorefast sea ice forms a platform that facilitates travel, camping, and hunting by Inupiat subsistence hunters and fishers in the western Arctic, the nearshore sea-ice zone remains an unforgiving and dynamic environment. Traditional hunters constantly hone site-specific experiences and skills with which to optimize the reward-to-risk ratio inherent in operating from this coastal ice. Nearshore ice conditions nevertheless can change suddenly, endangering even the most experienced subsistence hunters. This study examines two (of several) 20th-century events, 40 years apart, in which shorefast ice failed, threatening Inupiat whale hunters with loss of confidence, livelihood, and life. These events differed in character. In one event, the shorefast ice was "crushed" by moving ice floes. In the other, the shorefast ice broke free of land. Our examination focuses on the relationship of subsistence hunters to the ice, the environmental causes of ice failures, the evolving technology for predicting ice behavior, and the longer-term implications of global change for this system. The complexity of geophysical processes underlying coastal ice behavior makes ice failures unpredictable. Thus, hunters must assume and manage risk. The variable and uncertain environment to which whale hunters are accustomed has produced an inherent flexibility that has helped them adapt to new conditions and will continue to do so in the future.