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

Abstract

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.

More intensive ice melting and turbulent exchange under the ice in the areas of the jet-like currents on Lake Baikal

“…The difference in the ice thickness between the background station 1 and the station near the thawed patch at the end of March was 25 cm (inset in Fig.). This is comparable with the difference in the ice thickness between the centre and periphery of the ring structure near Nizhneye Izgolovie Cape (24-32 cm according to Kouraev et al, 2019) as well as the ring structure studied in 2009 near the Kultuk settlement (27-31 cm according to Granin et al, 2015;2018).…”

“…At this time, a dark area appears in satellite images, where the ice thickness is less than in the surrounding area, and the water level in microcracks is closer to the surface of the ice. An analysis of satellite images indicated more than 50 ice ring formations on Lake Baikal since 1969 (Granin et al, 2015;2018;Kouraev et al, 2016;2019). Study of field research data revealed that ice ring structures form due to circle anticyclonic currents under the ice.…”

Mapping potential signs of gas emissions in ice of Lake Neyto, Yamal, Russia, using synthetic aperture radar and multispectral remote sensing data

“…Cohen's κ is especially used to measure inter-rater reliability. In the interpretation scheme proposed by Landis and Koch (1977), κ from our validation belongs to the category "substantial agreement". A drawback is that we cannot present a proper validation against ground truth data, as often anticipated in remote sensing studies, but the remoteness of the study area and the potential endangering of human safety largely restricts in situ data collection on-site (see also Sect.…”

“…Our approach again utilises the dual-polarisation capability of Sentinel-1 and tests the similarity between classification outcomes of the two polarisation channels using Cohen's kappa score κ (Cohen, 1960). Only if κ was above 0.2 (class "fair agreement" according to Landis and Koch, 1977), was the final classification produced as described above. If κ was below 0.2, all pixels in the image were assigned to the negative class.…”

Hydrogen-carbon dioxide anomaly within the boundaries of the Holy Nose ring ice structure formation (Svyatoy Nos Peninsula)

“…The external morphology of the ring structure has changed significantly to the time of the survey on 11.04.2016 since its first occurrence on 14.04.2016 (dynamics of change in Kouraev et al, 2019). The object was a round-shaped area ~ 7*8 km in size (slightly elongated in the NE direction).…”