Development of microstructure measurements meeting the Baltic Sea conditions

Abstract

The principal physical research tasks addressing environmental problems of the Baltic Sea are the study of ventilation of the deep water and of vertical mixing. To achieve a progress, direct measurements of fine- and microstructure of water are necessary. Instrumentation to do this has been developed successfully; nevertheless the water structure in the Baltic Sea is so tricky that existing techniques need special adaptation and improvement. This paper presents several types of profilers: cycling profilers both towed and moored, and freely sinking or floating probes. Some of them perform direct microstructure measurements while others are necessary to obtain a properly resolved background measurement of thermohaline and current structure. We consider freely-moving CTDs as an alternative for direct dissipation measuring meters if the probe's motion is stable enough and its spatial resolution is high enough. Having in mind the Baltic conditions, special attention is paid to fine measurements close to the sea surface and within the bottom boundary layer. We try to adjust such instruments for use from small inexpensive boats, so we hope fine- and microstructure measurements will be more accessible.