Coldness contributes significantly to the representation and definition of the Arctic. Thus, in a context of global warming, does the Arctic not reduce mechanically? Similarly, its common social representation associates it with a low-density settlement and traditional economies. Does accelerating integration of the boreal regions not affect their degree of nordicity? The index of nordicity of Louis-Edmond Hamelin dates back to the 1960s and the author has already pointed out effects of retraction and extension (Hamelin, 1968). This composite index still holds a special place (Petrov, 1977). It combines 10 criteria: one is latitude, six concern physical environment and, four concern human environment. For each of them, a place takes points according to its degree of nordicity. Finally, the sum of all its points forms its polar value. L.-E. Hamelin thus defined 'isonorths', lines of equal degree of nordicity, the one of ‘200’ laying the southern limit of the Arctic. We are attempting to update this index using as much as possible abundant, global and free downloadable databases. In order to get a view of spatio-temporal evolution of the ‘isonorths’, the nordicity index is calculated for the years 1960 and 2010. This presentation focuses on the first part of this work, which concerns the physical environment, ie 6 out of 10 criteria. A raster with a spatial resolution of 25 km x 25 km is developed for each criterion. Then, a conversion of the data into points of nordicity is carried out according to a matrix adapted from L.E. Hamelin. Finally, the new raster is added to the stack to make the final sum. The results for the environmental criteria show, on the scale of the Arctic basin, a retreat towards the north of the isonorths. Regional disparities appear and are discussed. The case study of Western Siberia for which all the criteria have been calculated could be presented.