The Arctic sea-ice cover has undergone remarkable recent change, exceeding that projected for the current decade with climate models under increasing carbon dioxide forcing. While research with sophisticated regional climate models focuses on this change, there are still open questions regarding the basic nature of sea-ice processes and their correct representation in such numerical models. Ridging is one of them. Including ridging in the aforementioned models results on the one hand in thicker ice, which increases the internal force in the momentum balance and the lifetime of the ice in the melting season, and on the other hand in more open water within the ice cover, enhancing ice growth (melt) in winter (summer). This study has two parts. Part one deals with the analysis of sea-ice motion and thickness measurements obtained during the Sea Ice Experiment – Dynamic Nature of the Arctic (SEDNA) based at the APLIS07 field camp in the Beaufort Sea. Two hexagons of GPS drifters, with radii of 10 and 70 km, were placed on the ice in April 2007. The buoy positions were used to derive stress and strain rate components of the ice pack. During this time repeated airborne measurements of the ice thickness were performed with a ‘HEM-bird’ along the spokes and perimeter of both hexagons. The HEM-bird enables the simultaneous profiling of the ice underside with an electromagnetic device and the ice surface with a laser altimeter, their difference yielding the ice thickness. By co-locating the HEM flight tracks with additionally acquired SAR images we evaluate the general ice conditions and interpret the ice-thickness observations. We use this information to access the thickness distribution changes during the ridging process. In the second part a 1-D ridging model, which is typically used in regional-scale coupled sea-ice–ocean simulations performed with grid resolutions of 3–30 km, is applied to single observation lines. The model is initialized with the observed ice-thickness distribution of the first HEM-bird flights. Rates of divergence and shear obtained from the buoy arrays serve as forcing for the ridging model. The model also accounts for thermodynamic sea-ice growth forced by surface air temperatures frequently sampled at the camp site in order to estimate sea-ice production in particular in leads forming during the period of the experiment. The second set of ice-thickness measurements is used to evaluate the model.