Giant ice rings on lakes and field observations of lens-like eddies in the Middle Baikal (2016–2017)

Giant ice rings (diameter 5–7 km) detected on lakes Baikal (Russia) and Hovsgol (Mongolia) are a surface manifestation of intrathermocline lens-like eddies under ice cover. By analyzing satellite imagery, we have detected new ice rings in 2016 and very old ones in 1969 for Lake Baikal. We have also discovered a giant ice ring on a new water body—Lake Teletskoye in the Altai Republic (Russia). Our recent field observations in the Middle Baikal have high temporal and spatial resolution and coverage and include temperature and current measurements over a long (1.5 month) period. In 2016, an eddy was detected in February and then an eddy and ice ring were detected in March at the same location. In 2017, another eddy was detected in February. This eddy was not stationary, as it was detected 6 km from its initial position in March, and thus no ice ring formed. The results of our field observations provide new data on the size and shape of the eddies. Indirect and direct measurements of currents and temporal evolution of the temperature field make it possible to estimate the rotation period (3 d) for the eddy in 2016 and assess the timing of movement, position, and displacement speed of the eddy in 2017. Thermal infrared Landsat imagery before ice formation in November–December 2015 shows that the eddy in 2016 was formed by the wind-induced outflow from the Barguzin bay.