Palsas develop as permafrost aggradation uplifts peat out of the zone influenced by groundwater. Here we relate N-15 values to C/N ratios along depth profiles through palsas in two peatlands near Abisko, northern Sweden, to identify perturbation of the peat. The perturbation by uplift as well as the potential nutrient input from the adjacent hollows can be detected in soil N-15 values when related to the C/N ratio at the same depth. Nine out of ten profiles show a perturbation at the depth where peat was uplifted by permafrost. Palsa uplift could be detected by the N-15 depth pattern, with the highest N-15 values at the so-called turning point. The N-15 values increase above and decrease below the turning point, when permafrost initiated uplift. Onset of permafrost aggradation calculated from peat accumulation rates was between 80 and 545years ago, with a mean of 242 ( +/- 66) years for Stordalen and 365 ( +/- 53) years for Storflaket peatland. The mean ages of permafrost aggradation are within the Little Ice Age. Depth profiles of N-15, when related to C/N ratio, seem to be a suitable tool to detect perturbation and uplift of palsas. Copyright (c) 2016 John Wiley & Sons, Ltd.