Examples and effects of avalanches on the surface of mountain lakes: Morskie Oko, a case study from Poland (Tatra Mountains)

Abstract This study represents a pioneering effort to analyze the impact of avalanches descending into Morskie Oko from Marchwiczny Gully, the most active avalanche path around the lake. It focuses on catastrophic avalanches that descended from the analyzed gully, as reported in the literature from the 1900s until now. However, only the data collected in recent years, our field studies, combined with modern LIDAR data and GIS-based modeling, allowed us to perform a detailed analysis. The GIS-based approach effectively uses spatial data to address snow avalanche modeling challenges. Although the study area lies within Tatra National Park, no official services carry out systematic avalanche monitoring or measurements. The impact of hazardous events, such as snow avalanches, on the most famous Polish mountain lake, Morskie Oko, has been poorly described in the literature and has yet to be discovered. Therefore, to analyze the selected avalanche parameters, we mainly used our ground and additional aerial photographs taken by local mountain services and related field measurements. Our analysis resulted in figurative estimates of the extent and volume of avalanche snow and its weight, both on the surface of the ice sheet and the part of the avalanche that did not reach the lake’s shore and remained on the slope of Marchwiczny Gully. For example, the values for the mighty avalanche on February 3, 2023, are 23,500 m 3 and 4,700 tons on the ice surface and 20,000 m 3 and 4,000 tons on the slope. It was determined that avalanches that descend onto the studied lake’s surface result in its shallowing. This process occurs because of sedimentation of slope material carried by avalanches, especially during the final phase of ice cover melting. When openings appear in the solid ice cover in spring, floating ice can migrate, driven by wind pressure, and deposit avalanche material in various parts of the lake bottom. Thus, avalanches contributed to the gradual disappearance of the lake.