An ice massif is a significant quasi-stationary accumulation of close or very close sea ice (with an ice concentration ranging from 7 to 10 tenths, and the concentration is the ratio expressed in tenths describing the amount of the sea surface covered by ice as a fraction of the whole area being considered, according to WMO Sea Ice Nomenclature). Ice massifs cover hundreds of square kilometers and are found in the same region every summer melting period.

Being an obstacle to navigation, ice massifs were first discovered in the 1940s with the help of air reconnaissance. These are also of interest now, since the development of the Arctic Sea shelf and related activities require safety and timing of work. We used data from the electronical archive of the Arctic and Antarctic Research Institute (AARI). The archive contains information on the year-round distribution of the ice cover in the form of maps and quantitative estimates of Arctic ice cover, including ice massifs. For assesment of interannual variability of ice massifs, we used a data set of quantitative estimates since 1940 to 2024 for June–September. For assessment of spatial distribution, we used regional Laptev Sea charts of the ice conditions, compiled by the AARI for June–September in 1997–2024. These data were analyzed using the method of probability calculation with polygon intersections. There are two ice massifs in the Laptev Sea: the Yansky ice massif, formed by fast ice in the eastern part of the sea, and the Taimyrsky ice massif, formed by a narrow fast ice and drifting ice in the western part of the sea. In summer, the Taimyrsky ice massif is fed by ice coming from the Arctic basin. By the end of the melting period, the Taimyrsky ice massif rarely disappears completely. However, during recent decades, the frequency of these events has increased. The Yansky massif consists mainly of fast ice, which lasts for a long time at the beginning of the summer period and quickly collapses after fast ice destruction. The Yansky massif disappears completely with very high frequency.