The Arctic sea-ice cover is undergoing dramatic changes in its extent and thickness. As part of the Arctic Observing Network, autonomous drifting buoys have been successfully used to observe the mass balance of perennial ice, providing important insights on ice growth and melt. The shift from perennial to seasonal ice in large portions of the Arctic has reduced survivability of the current buoy design. This has created a need for a new autonomous system capable of operating in thin ice or open water. The new design we present is based on a spar buoy which is equipped with acoustic sensors above and below the ice. These sensors measure surface and bottom position, providing snow depth, ice thickness, ice growth, surface melt and bottom melt. The buoy also has a thermistor string to measure a vertical profile of air–snow–ice–ocean temperature, a barometer, a GPS to determine position and an Iridium transmitter to send data back from the field. Addition sensors can be added for specialized studies. The buoy hull is designed to float upright with a strong righting moment enabling it to operate without the support of a surrounding ice cover. Results from deployments of the new buoy in the seasonal ice zone of the Beaufort Sea are presented.