Engineering Physics Annotation << Back Peculiarities of Modulation Instability of Flexural-Gravity Waves in Seas with Ice Cover Zubarev N.M., Stepanyants Yu.A. The use of hydrodynamic equations taking into account boundary conditions on the liquid surface within the framework of the elastic thin plate model gives rise to flexural-gravity waves (FGW). The properties of these waves in the linear approximation have been studied in many articles and monographs. Much fewer publications are devoted to nonlinear processes occurring in the ice-water system. A weakly nonlinear theory of such waves was developed in a number of works, in which, in particular, the nonlinear Schrödinger equation (NLSE) was derived for specific cases. A general analysis of the modulation instability for the main control parameters was carried out by Slyunyaev and Stepanyants, 2022. Using the Lighthill criterion, conditions were found under which a quasi-sinusoidal wave becomes unstable with respect to amplitude modulation. At the boundaries of the modulation instability zones, the standard NSE equation becomes unsuitable, which requires its generalization. In this paper, it is shown that in cases where the dispersion coefficient of the NLSE vanishes, taking into account the effects of the next order of smallness generates a generalized NLSE, which also has solutions in the form of envelope solitons with specific properties. When the compression of ice reaches a certain threshold value, the linear theory predicts the occurrence of buckling phenomenon, deformation, and destruction of the ice plate. In this paper, it is shown that under slightly supercritical compressions, various dynamic modes of oscillations of the ice plate can exist. Estimates of the characteristic parameters of wave disturbances are presented using real physical data. Keywords: Ice cover, flexural-gravity waves, modulation instability, envelope soliton. DOI: 10.25791/infizik.10.2025.1506 Pp. 03-16.