A simple model for seawater crystallization in the temperature spectrum

A model of sea ice growth as an expanded region of a phase transition (mushy zone) with a linear temperature profile is developed. The linear temperature distribution agrees with the mushy zone by introducing an equivalent porosity determined by its thermodynamical condition. This approach does not require any a priori information about the dependence of the porosity on the temperature and salinity; it rather allows us to obtain this relation from a solution of the mathematical problem. The model makes it possible to calculate the thickness of the growing ice and to estimate its main characteristics as well as the heat capacity of the underice layer under the conditions of undisturbed growth at any moment of the autumn-winter season up to its maximal thickness with account for the snow accumulation, basin depth, varying regime of cooling, and water salinity.     

Thermodynamics of freezing puddles in the autumn-winter period

The results of the field observation of freezing melted puddles on the drift ice in the Arctic Basin carried out in July–September of 2005 during cruise 23 of R/V Akademik Fedorov are analyzed, and a thermodynamical model of the process based on these results is developed. The essential features of the evolution of puddles in the period of autumn cooling were revealed. The unfrozen liquid layer was shown to be a qualitative component of the system that defines its behavior as a whole. We concluded that the sea ice growing from below is absent until the thickness of the frozen water reaches a critical value that is determined by its initial salinity.     

Flow Structure near an Island in a Shallow Strait

The problems of flow dynamics in a near-island zone of a shallow channel is considered using as an example the Bjerkezund Strait (eastern Gulf of Finland). Preliminary results of field studies and the results of numerical modeling of water circulation in the strait are given.     

Influence of melt ponds on the formation of the multiyear sea ice cover

The features of the sea ice growing and melting under the modern climatic conditions are considered with the use of the thermodynamic model of sea ice taking into account the seasonal melting and recrystallization of its upper layers. The evolution of the snowy and icy cover for the North Pole geographic point is estimated quantitatively on the basis of the NCEP/NCAR 2007 atmospheric reanalysis data.     

Structure of the Fram Strait branch of the boundary current in the Eurasian Basin of the Arctic Ocean

Recent mooring-based observations at several locations along the continental slope of the Arctic Ocean's Eurasian Basin showed a transformation of the Boundary Current (BC) from a mostly barotropic flow in Fram Strait to a jet-like baroclinic current northeast of Svalbard, and the reemergence of the barotropic structure of the flow in the eastern Eurasian Basin. This transformation is accompanied by a weakening of the flow from ～24 cm/s in Fram Strait to ～5 cm/s at the Lomonosov Ridge. The maximum of the baroclinic component of the BC at an intermediate depth (～200–370 m) is associated with the Atlantic Water core. The depth range of the baroclinic current maximum is controlled by cross-slope density gradients above and below the baroclinic velocity maximum as follows from the geostrophic balance of forces. According to the model simulations, the BC splits into shallow and deep branches in the proximity of Svalbard due to a divergence of isobaths, confirming topographically-controlled BC behavior. The shallow branch is located at a shelf break with a typical bottom depth of ～200 m and current speed of up to ～24 cm/s. The discussed results, which provide insight on some basic aspects of the dynamics of the BC (the major oceanic heat source for the Arctic Ocean), may be of importance for understanding of the ocean's role in shaping the arctic climate system state.