Frozen ocean waves4/5/2023 Notwithstanding the importance of atmospheric and oceanic forcing, by these agencies ocean waves exert a material influence on pack ice that has been overlooked in most MIZ studies to date. Here the process is one of rafting and ridge-building, which is common near the ice edge, and of the piling-up of frazil ice during freezing periods at the beginning of the pancake-ice cycle as reported by Reference Wadhams, Lange and AckleyWadhams and others (1987). While wave-induced changes to ice thickness are more esoteric, they can and do occur. in this case, the waves break up floes that are too big, causing a gradual conversion from one floe-size distribution to another thai depends on the relationship between floe size and the dominant wavelengths of the incoming swell, and on wave height. Floe-size distribution is under the direct control of waves. Concentration, besides reacting quickly to changes in currents and wind, is altered by the lateral pressure that waves exert on floes, which leads to differential drift and causes them to aggregate into belts of similar-sized floes or bands. The intense ocean-wave fields associated with the Southern Ocean penetrate deep into the sea-ice marginal ice zone (MIZ), causing changes in the concentration, the lloe-size distribution and, particularly near the ice edge, the distribution of thicknesses (Squire and others, 1995). The cumulative effect of these details has wide significance. When present, sea ice is described by its type, by its thickness and roughness, by the amount of sea surface occupied by ice, namely, concentration, and by the distribution of ice-floe sizes. Especially for the Southern Ocean, where the sea ice occupies some 20 x 10 6 km 2 at maximum extent (September-October) but only 3 x 10 6 km 2 in February, the extreme variability is responsible for many attributes of Southern Hemisphere climate, for features relating to ocean structure and for biological community distribution in time and space. Howard-Williams and StantonCarter and others, 1997). It also has significant océanographie influence due to the release of relatively dense brine during freezing and low-salinity water as the sea ice melts, and this, together with its capacity to inhibit light and carbon-dioxide exchange, means that sea ice has a pronounced biological influence ( Reference Carter, Bradford-Williams, C. As such, it has an appreciable effect on local meteorology and, over longer time-scales and large spatial scales, on climate. Sea ice alters the exchanges of energy, momentum and gas between the atmosphere and the ocean ( Reference Worby, Jeffries, Weeks, Morris and JañaWorby and others, 1996). These indicate that fatigue may be a neglected ingredient of sea-ice failure due to wave-induced motion. Using theory and data from wave experiments performed in similar conditions to the fatigue experiments, estimates are made of the conditions under which wave-induced break-up occurs. These tests suggest that an endurance limit exists for sea ice, and that it is approximately 60% of the flexural strength. We report a scries of field experiments to investigate the fatigue behaviour of first-year sea ice that subjected in situ cantilever beams to repeated bending with zero mean stress. This stress is termed the endurance limit. in some materials a stress exists below which the material will maintain its integrity even if subjected to an infinite number of load cycles. Many materials fail at stresses well below their flexural strength when subject to repeated bending, such processes being termed fatigue. This, together with any redistribution due to ocean currents or winds, alters the fluxes between the atmosphere and the underlying ocean. The manner in which sea ice breaks up determines its floe-size distribution.
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