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Satellites enable daily and global coverage of the polar oceans and provide a unique monitoring capability of sea ice dynamics. Sea ice drift maps can be estimated in Arctic from several satellite sensors, particularly from scatterometers and radiometers. This study presents the benefits of combining single drift fields at the same resolution into a “merged” field, built at three- and six-day lags during winters with a 62.5-km resolution. It is shown that combining these drift fields not only increases the reliability of the displacement estimation and the number of estimated vectors to almost a full ice covered area but also expands the time period over which these estimations are reliable from freeze until the melt onset. The autumn-winter-spring sea ice drift fields presented here are systematically produced at Institut Français de Recherche pour l'Exploitation de la Mer/Centre d'Exploitation et de Recherche Satellitaire, the sea ice drift 1992-2011 time series is available, and the processing is ongoing. These data are available for operational use and for the scientific community. [ABSTRACT FROM AUTHOR]

Sea surface wind speed and significant wave height (SWH) are two basic parameters, in addition to sea surface height, which can be inferred from satellite altimeter measurements. Traditionally, altimeter-derived wind and wave data are less extensively used compared to sea surface height, as they are sometimes considered as by-products of satellite altimetry (in contrast to, for example, the dedicated scatterometer missions for marine wind observations). However, it is clear that altimeter-based wind and wave data have the unique advantage of being concurrent and collocated with each other. Using eight years (1993–2000) of TOPEX altimeter data with unprecedented accuracy and continuity, the 10-, 50- and 100-year return values of global wind speed and SWH are derived, their characteristics are discussed in relation to wind climatology and wind variability. Validations against in situ observations indicate that the uncertainties of altimeter-derived extreme winds and waves are at the levels of 10% and 5%, respectively. These results suggest that satellite altimeter data, with present quality and duration, can be very useful in many aspects of coastal engineering and marine technology such as design of offshore facilities, ship routing, and preparation of other sea-going activities. [ABSTRACT FROM AUTHOR]

The variation of the Southern Ocean (SO) sea level and its possible relation with Antarctic sea ice are investigated. The dataset used results from a space-time objective analysis which merges one-year simultaneous ERS-1 and TOPEX/POSEIDON altimeter data. The main results are as follows, (1) The study confirms and complements previous ones in that the sea level variability in the SO is complex and bathymetrically controlled. The Antarctic Circumpolar Current is dominated by the annual component. For the western boundary currents, however, the semi-annual component is equally or more important. (2) A new result is obtained showing that, in the Brazil/Malvinas Confluence region, the locations of the annual and semi-annual energies are geographically separated, the maxima of which are comparable instead of being semiannual dominant. (3) A striking feature revealed by this study is that the annual cycles of sea level variations in the western boundary current zone (35degree-45degree S) and seasonal sea ice zone (60degree-70degreeS) are nearly 180degree out of phase. This suggests that two contrary governing processes, speculated to be the solar cycle and sea ice cycle, co-exist in the SO. (4) It is argued that the variations of the SO sea level and Antarctic sea ice are strongly coupled through steric effect as well as insulating effect of the sea ice cover. [ABSTRACT FROM AUTHOR]

Bifurcations in dynamical systems are often studied experimentally and numerically using a slow parameter sweep. Focusing on the cases of period-doubling and pitchfork bifurcations in maps, we show that the adiabatic approximation always breaks down sufficiently close to the bifurcation, so the upsweep and downsweep dynamics diverge from one another, disobeying standard bifurcation theory. Nevertheless, we demonstrate universal upsweep and downsweep trajectories for sufficiently slow sweep rates, revealing that the slow trajectories depend essentially on a structural asymmetry parameter, whose effect is negligible for the stationary dynamics. We obtain explicit asymptotic expressions for the universal trajectories and use them to calculate the area of the hysteresis loop enclosed between the upsweep and downsweep trajectories as a function of the asymmetry parameter and the sweep rate.