AbstractLocal and transect ice-thickness measurements were performed between May and November 2007 on an ice floe in the Transpolar Drift of the Arctic Ocean using an ice mass-balance buoy and electromagnetic induction (EM) sounding. Repeated EM surveys along an originally 2160m long profile including level and deformed ice showed that between June and September modal and mean thicknesses decreased by 0.6 and 0.86m respectively. the modal thickness decrease is in good agreement with the thinning of 0.6m observed by the ice mass-balance buoy at one location on unponded ice during the same period, although the local observations do not capture the different melt rates on level and rough ice. the paper discusses methodological and operational challenges in sustaining both measurements over periods of several months, and concludes that more work needs to be done to better understand their representativeness.