Experimental evidence for a universal threshold characterizing wave-induced sea ice break-up

Waves can drastically transform a sea ice cover by inducing break-up over vast distances in the course of a few hours. However, relatively few detailed studies have described this phenomenon in a quantitative manner, and the process of sea ice break-up by waves needs to be further parameterized and verified before it can be reliably included in forecasting models. In the present work, we discuss sea ice break-up parameterization and demonstrate the existence of an observational threshold separating breaking and non-breaking cases. This threshold is based on information from two recent field campaigns, supplemented with existing observations of sea ice break-up. The data used cover a wide range of scales, from laboratory-grown sea ice to polar field observations. Remarkably, we show that both field and laboratory observations tend to converge to a single quantitative threshold at which the wave-induced sea ice break-up takes place, which opens a promising avenue for robust parametrization in operational forecasting models.Comment: 18 pages, 8 figures, 1 tabl

Wave modelling - the state of the art

This paper is the product of the wave modelling community and it tries to make a picture of the present situation in this branch of science, exploring the previous and the most recent results and looking ahead towards the solution of the problems we presently face. Both theory and applications are considered. The many faces of the subject imply separate discussions. This is reflected into the single sections, seven of them, each dealing with a specific topic, the whole providing a broad and solid overview of the present state of the art. After an introduction framing the problem and the approach we followed, we deal in sequence with the following subjects: (Section) 2, generation by wind; 3, nonlinear interactions in deep water; 4, white-capping dissipation; 5, nonlinear interactions in shallow water; 6, dissipation at the sea bottom; 7, wave propagation; 8, numerics. The two final sections, 9 and 10, summarize the present situation from a general point of view and try to look at the future developments

The form of the asymptotic depth-limited wind-wave spectrum part II: the wavenumber spectrum

Data from a spatial array of wave gauges is analysed using the Wavelet Directional Method (WDM) to directly determine the wavenumber spectrum. The data shows that the asymptotic depth-limited wavenumber spectrum can be represented as a two-parameter form, which is far simpler than the corresponding frequency spectrum. The WDM analysis shows that there are significant nonlinear processes active in the finite depth water, which results in energy being "smeared" across a range of wavenumbers and frequencies around the standard dispersion shell. As a result, the wavenumber spectrum has much less peak enhancement than seen in the frequency spectrum obtained with standard Fourier analysis. In addition, the wavenumber spectrum does not have the clear harmonic previously observed in the finite depth frequency spectrum. This result demonstrates that the harmonic is nonlinearly phase-locked to the spectral peak

The depth-limited wind-wave spectrum

This paper describes a comprehensive field experiment aimed at determining the form of the asymptotic, depth-limited wind-wave spectrum. The data clearly defines the limit in terms of total energy and peak frequency. In addition, the forms of both the frequency and wavenumber spectra are defined. The influence of nonlinear processes and Doppler shifting are clear. As a result of these processes, the usefulness of the frequency spectrum in such depth-limit ed conditions is questioned

Modelling wind-generated waves at moderate-to-extreme conditions

Abstract not available

The decay rate of ocean swell observed by altimeter

Altimeter data from transects across the Southern Ocean are analyzed to determine the decay of oceanic swell. The resulting decay rate is shown to be proportional to wavenumber squared and swell amplitude cubed. Such a decay relationship is consistent with turbulent interaction with the background, either in the air or water. The present data cannot distinguish between these two cases. The results are consistent with the limited previous studies and present a source term suitable for use in wave prediction models