To study the snow microstructure at various metamorphism times and extract the snow neck area, a constant density (200 kg/m³) snow metamorphism experiment was conducted. The findings show that the neck region is mostly influenced by temperature, sun radiation, snow density and specific humidity, with wind speed having little effect. Additionally, we developed a multiple linear regression equation for the neck area under atmospheric forcing: “S = 288T + 2E + 189ρ + 12,194V − 20,443RH − 42,729”. This equation accounts for solar radiation (E), temperature (T), snow density (ρ), specific humidity (RH) and wind speed (V). Notably, the above five factors can account for 84% of the factors affecting the neck area, making it a crucial factor. The relationship between snow hardness and neck area is correlated at 71%, and in later stages of metamorphism, the correlation may increase to 91%. Based on the neck area, the following hardness value prediction is made: “H = 0.002764S + 67.922837”. This study documents the growth variations in the neck region of the metamorphic snow cover and elucidates the process by which outside factors impact the microstructure and macroscopic physical characteristics of the snow cover.

Global warming reduces the thickness and duration of seasonal lake ice, increasing the risk of ice cover failure. To investigate the bending behavior of ice cover, six groups of full-scale cantilever beam tests were conducted on a brackish water lake during the winter of 2023–2024, covering the following three ice periods: growth, stable, and melt. A total of 16 upward-loaded beams and 24 downward-loaded beams were tested. The results showed that the flexural strength of brackish ice was 374.21 ± 99.93 kPa, and the effective elastic modulus was 2.77 ± 0.93 GPa. The square root of bulk porosity, fitted with an exponential function, is the optimal predictor of flexural performance. Both flexural strength and effective elastic modulus systematically decreased with increasing porosity, and empirical regression formulas were established. On average, downward-loaded flexural strength was approximately 17.3% to 38.8% higher than upward-loaded strength, whereas elastic modulus showed no significant difference between the two loading directions. Flexural mechanical properties during the melt period reduced significantly, with a strength and modulus about 33.0% to 61.1% lower than those in the growth and stable periods. Comparisons with existing datasets demonstrate that the mechanical properties of brackish ice are lower than those of freshwater ice but higher than those of sea ice. This study provides new in situ data on the full-scale flexural mechanical properties of brackish ice and offers an important basis for assessing ice loads in lakes and estuarine environments under climate change.

Under global warming, lateral melting plays an increasingly important role in heat exchange between ice and water. However, field-based observations of its depth-dependent behavior remain limited, hindering the development of reliable parameterizations. To address this, we performed continuous in situ measurements of lateral melting at Lake Hanzhang. Lateral melting rates at depths of 10, 20, 30, and 35 cm during the melt period were measured and analyzed. Total lateral melt amounts over the observation period were 64 mm at 10 cm, 84 mm at 20 cm, 148 mm at 30 cm, and 176 mm at 35 cm, revealing a pronounced depth-dependent gradient. This gradient was accompanied by distinct vertical differences in ice temperature, with the upper layer responding more closely to air temperature and the lower layer to water temperature. With rising air temperatures from −12 °C to above-zero and water temperatures from 2 °C to 4 °C, the lateral melting rate increased from 2 mm·h⁻¹. A parameterization scheme linking the ice–water temperature difference to the lateral melting rate was developed for different air temperature regimes. Notably, observed lateral melting under sub-freezing air temperatures provides a reference for non-summer conditions. In addition, lateral melting accelerates ice thinning and open-water formation, which enhance heat absorption and ice transparency, thereby increasing water temperature and photosynthetically active radiation beneath the ice. These changes may promote primary productivity, supporting a potential linkage between lateral melting and the under-ice habitat environment. Collectively, the results offer a more realistic basis for parameterizing lateral melting in ice thermodynamic models.