Seasonal behavior of the CO₂ gas exchange process in the “atmosphere-water” system of littoral zone of Southern Baikal. 3. Autumn

Abstract

This paper is the next in a series of publications dealing with the analysis of seasonal features of the carbon dioxide exchange process in the littoral of the Southern Baikal during the open-water period, and devoted to results obtained during the fall period. It is shown that variations in the concentrations of dissolved gases and biogenic elements in the surface waters of the Lake Baikal littoral during fall are opposite in character to the process observed during the spring-summer period. The concentrations of carbon dioxide, oxygen, nitrates, and phosphates increase from the second half of September toward December. The sink of CO₂ from the atmosphere into the water surface is still observed during early October in the Baikal littoral, with its diurnal budget being comparable in value to the daily average sink during the period of hydrological summer. The daily average CO₂ flux reverses sign in November, and the lake surface becomes a source supplying carbon dioxide to the near-water atmosphere; the CO₂ supply rate keeps increasing and reaches a maximum level during December, i.e., until the beginning of freezing-over period. At the beginning of this period, an additional small CO₂ amount can be expected to be supplied to the atmosphere of the littoral zone due to the process of premorning freezing and a subsequent ice melt.