Annual temperature regime of the shallow zone of Lake Baikal inferred from high-resolution data from temperature loggers

Abstract

Annual changes in temperature characteristic of the shallow zone during 2017-2022 have been studied in this work. Dataset was contrasted based on 8 transects located in South, Central and Northern Baikal at depths of 3, 4, 6, 12, 15 and 26 m. Temperatures were measured every 1.5-3 hour. It was determined that modal values of maximal heating of the shallow zone at all stations and depths were 15-16°C, however, distribution of maximal temperatures of South Baikal shifted toward the low temperatures, and these maximums could be only 9-10°C. Temperature regime of the shallow zone during warm seasons is characterized by sharp changes due to wind mixing and upwelling, when temperature drops dramatically from 16-18°C to 4°C for the 1-1.5 day. In most cases, the duration of stabile temperature condition without wind mixing was 4 days. On average, upwelling events occurred 5 times (maximum - 13 events) from July to November. As a result of wind mixing, the shallow zone is characterized as moderately warm with average temperatures of 6-7°C from June to November. A temperature effect on the shallow zone of Lake Baikal due to the Global warming is smoothed by cooling of the zone by deep waters during upwellings.