It is known that considerable part of living matter in the ocean falls out of biological cycle irretrievably by way of sedimentation. It means that quasi-stationary state of oceanic ecosystems is possible only with supply of mineral and organic matter from land. That supply, which includes also contaminating matter, takes place mainly in near-shore regions, concentrates in bottom boundary layers, and is transferred to the open sea via shelves by means of horizontal and vertical mixing. Effective mixing in shelves is carried out by small-scale processes, which are considerably fed by energy of large-scale processes from out-of-shelf regions. The main objective of our paper is to identify mechanisms of energy transfer from large to small-scale motions and from open sea to near-shore areas. Our experiments and observations in the shelf zone of the Sea of Japan revealed important specific features in stratified bottom boundary layers: 1) Temporal intermittence of internal waves (IW) in near-bottom layers and their transformation into sequences of stratified boluses moving in non-stratified medium. 2) Extremely high horizontal and vertical velocities in the near-bottom layers. 3) Considerable power fluctuations caused by correlated fluctuations of near-bottom pressure and velocity. 4) Non-monotonic vertical structure of temperature and velocity leading to possibility of simultaneous existing of IW breaking and secondary generation of high-frequency IW by turbulence in layers with high curvature of velocity profiles. Taking into account satellite observations of high correlation between chlorophyll-a concentration in coastal and in out-of-shelf waters, as well as dispersion relations for different types of internal waves and results of our field experiments we suggest that interconnection of biological parameters in coastal and in open sea waters is exercised substantially by gravitational and inertial internal waves generated by tides and eddies in the region of continental slope near the shelf boundary.
Modeling of three-dimensional sound propagation through solitary internal waves
