Search

Apart from the mechanisms of ice structure interactions under various scenarios of sea ice conditions and structural configurations, the selection of probabilistic models is crucial in order to cope with the loading uncertainty. Sea ice is the primary contributor to design loads in cold regions. In many cases, ice loads present the highest magnitude. In recent years, the probabilistic study of ice thickness, ice strength coefficient, flexural strength, ice drift speed, etc., has significantly increased, corresponding to the increasing activity of offshore operations in cold regions as well as the development of instrument technology for sea ice observation. This paper reviews existing probabilistic modes of sea ice, which are used to estimate the uncertainty of ice loading with various types of offshore structures, including vertical structures, sloping structures, and stations with floating vessels. The ISO 19906 standard is employed for the probabilistic assessment of vertical and sloping structures. The interactions between ice and structures on sloping structures are considered in both the upward and downward directions. The ice resistance method is applied for station-keeping floating vessels in ice. The key parameters of sea ice properties to estimate the design loads are studied. The effect of correlation between the key parameters of ice loads is investigated. This review shows that most existing probabilistic models are proposed for the estimation of ice loading on the various types of offshore structures. [ABSTRACT FROM AUTHOR]

In the summer of 2020, ESA changed the orbit of CryoSat‐2 to align periodically with NASA's ICESat‐2 mission, a campaign known as CRYO2ICE, which allows for near‐coincident CryoSat‐2 and ICESat‐2 observations in space and time over the Arctic until summer 2022, where the CRYO2ICE Antarctic campaign was initiated. This study investigates the Arctic CRYO2ICE radar and laser freeboards acquired by CryoSat‐2 and ICESat‐2, respectively, during the winter seasons of 2020–2022, and derives snow depths from their differences along the orbits. Along‐track snow depth observations can provide high‐resolution snow depth distributions which are vital for air‐ice‐ocean heat and momentum transfer, understanding light transmission, and snow‐ice‐interactions. Generally, ICESat‐2 is backscattered at a surface above the elevation of the CryoSat‐2 signal. CRYO2ICE snow depths are thinner than the daily model‐ or passive‐microwave‐based snow depth composites used for comparison, with differences being most pronounced in the Atlantic and Pacific Arctic. Satellite‐derived and model‐based snow estimates show similar seasonal accumulation over first‐year ice, but CRYO2ICE has limited seasonal accumulation over multi‐year ice which is linked to a slow increase in ICESat‐2, and to some extent CryoSat‐2, freeboards. We present a first estimation of spaceborne along‐track snow depth estimates with average uncertainty of 10–11 ± 2–3 cm for 7‐km segments, with random and systematic contributions of 7 and 4 cm. These observations show the potential for along‐track dual‐frequency observations of snow depth from the future Copernicus mission CRISTAL; but they also highlight uncertainties in radar penetration and the correlation length scales of snow topography that still require further research. Plain Language Summary: Estimates of snow depth on sea ice are currently either outdated or limited in resolution, thus a need to derive high‐resolution snow depth on sea ice is crucial. Former studies have computed snow depth on sea ice using the difference in penetration between radar (Ku‐band) and laser (or Ka‐band radar) altimeters from different satellite missions, assuming the Ku‐band radar and laser/Ka‐band are reflected at the bottom and top of the snow pack, respectively. Those studies have resulted in monthly composites of snow depth due to a limited overlap of individual tracks between the satellite missions. Since the CRYO2ICE (CryoSat‐2/ICESat‐2 Resonance) campaign was initiated in July 2020, we have for the first time the possibility of investigating near‐coincident observations of spaceborne radar and laser altimeters. These results are important to initiate relevant discussions on snow depth retrieval in preparation for the future dual‐frequency altimeter mission, CRISTAL (Copernicus Polar Ice and Snow Topography Altimeter), expected to launch in 2028. Key Points: CRYO2ICE (C2I) orbits are investigated over sea ice for the first time and snow depth is computed along the orbitsC2I snow depth has an uncertainty of 10–11 cm along 7 km segments with 5–95% confidence interval of 7–16 cm for both winter seasonsAlong‐track snow depth is compared with modeled and passive‐microwave estimates and C2I is thinner for the Pacific and Atlantic Arctic [ABSTRACT FROM AUTHOR]

This technical note qualitatively and quantitatively describes the ice run that took place in Sokna river, Trøndelag, Norway on 23 January 2020. Metrological and hydrological data are described. Stranded ice floe size distribution data are presented and analysed. It is shown that the maximal ice floe dimension is well described by generalized exponential (shape parameter = 2.77, scale parameter = 1.42) or log-logistic distributions (alpha = 3.57, lambda = 1.15). A custom-built steel load panel had been mounted on Sokna bridge preceding the ice run; however, due to technical difficulties no forces were recorded. Hindcast calculations using Solidworks based on the permanent deflections experienced by this load panel have been carried out to estimate ice forces experienced by Sokna bridge. These hindcast calculations conclude that the real peak ice force experienced by the 0.8 m diameter cylindrical bridge piers must have been within the range 1.1 to 5.5 MN. This range is compared to predictions made by standards for predicting ice forces on bridge piers. This comparison reveals that the Norwegian standard, the lower bound of the SNiP standard, and the upper bound of the CSA S6:19 standard are consistent with this range, while the Swedish and Finnish standards predict too low forces. [ABSTRACT FROM AUTHOR]

Sea-ice ridges constitute a large fraction of the total Arctic sea-ice area (up to 40 %–50 %); nevertheless, they are the least studied part of the ice pack. Here we investigate sea-ice melt rates using rare, repeated underwater multibeam sonar surveys that cover a period of 1 month during the advanced stage of sea-ice melt. Bottom melt increases with ice draft for first- and second-year level ice and a first-year ice ridge, with an average of 0.46, 0.55, and 0.95 m of total snow and ice melt in the observation period, respectively. On average, the studied ridge had a 4.6 m keel bottom draft, was 42 m wide, and had 4 % macroporosity. While bottom melt rates of ridge keel were 3.8 times higher than first-year level ice, surface melt rates were almost identical but responsible for 40 % of ridge draft decrease. Average cross-sectional keel melt ranged from 0.2 to 2.6 m, with a maximum point ice loss of 6 m, showcasing its large spatial variability. We attribute 57 % of the ridge total (surface and bottom) melt variability to keel draft (36 %), slope (32 %), and width (27 %), with higher melt for ridges with a larger draft, a steeper slope, and a smaller width. The melt rate of the ridge keel flanks was proportional to the draft, with increased keel melt within 10 m of its bottom corners and the melt rates between these corners comparable to the melt rates of level ice. [ABSTRACT FROM AUTHOR]