58 research outputs found
Wind-driven zonal jets in the South Pacific Ocean
International audienceZonal jets west of the large islands of the South Pacific Ocean are predicted by theory, commonly seen in ocean models with sufficiently high resolution, and are beginning to be observed. These jets are often taken to reflect the blocking effect of the islands in the South Equatorial Current through ''Island Rule'' dynamics. Here it is shown that quasi-permanent structures of the basinwide wind field imply the existence of jets formed independently of the islands. Evidence for the existence of the wind-driven jets is found in climatological geostrophic currents. The hydrographic structures that produce the jets occur well below the thermocline
Dynamical Systems approach to Saffman-Taylor fingering. A Dynamical Solvability Scenario
A dynamical systems approach to competition of Saffman-Taylor fingers in a
channel is developed. This is based on the global study of the phase space
structure of the low-dimensional ODE's defined by the classes of exact
solutions of the problem without surface tension. Some simple examples are
studied in detail, and general proofs concerning properties of fixed points and
existence of finite-time singularities for broad classes of solutions are
given. The existence of a continuum of multifinger fixed points and its
dynamical implications are discussed. The main conclusion is that exact
zero-surface tension solutions taken in a global sense as families of
trajectories in phase space spanning a sufficiently large set of initial
conditions, are unphysical because the multifinger fixed points are
nonhyperbolic, and an unfolding of them does not exist within the same class of
solutions. Hyperbolicity (saddle-point structure) of the multifinger fixed
points is argued to be essential to the physically correct qualitative
description of finger competition. The restoring of hyperbolicity by surface
tension is discussed as the key point for a generic Dynamical Solvability
Scenario which is proposed for a general context of interfacial pattern
selection.Comment: 3 figures added, major rewriting of some sections, submitted to Phys.
Rev.
Basin-wide estimates of the input of methane from seeps and clathrates to the Black Sea
Avaliação dos coeficientes de digestibilidade dos aminoácidos do grão de trigo e seus subprodutos para frangos de corte utilizando diferentes metodologias
Reconstruction of local sea levels at South West Pacific Islands - a multiple linear regression approach (1988–2014)
Rising sea levels are a critical concern in small island nations. The problem is especially serious
in the western south Pacific, where the total sea level rise over the last 60 years has been up to 3 times the
global average. In this study, we aim at reconstructing sea levels at selected sites in the region (Suva,
Lautoka—Fiji, and Noumea—New Caledonia) as a multilinear regression (MLR) of atmospheric and oceanic variables. We focus on sea level variability at interannual-to interdecadal time scales, and trend over the
1988–2014 period. Local sea levels are first expressed as a sum of steric and mass changes. Then a dynamical
approach is used based on wind stress curl as a proxy for the thermosteric component, as wind stress curl anomalies can modulate the thermocline depth and resultant sea levels via Rossby wave propagation.
Statistically significant predictors among wind stress curl, halosteric sea level, zonal/meridional wind stress
components, and sea surface temperature are used to construct a MLR model simulating local sea levels.
Although we are focusing on the local scale, the global mean sea level needs to be adjusted for. Our reconstructions provide insights on key drivers of sea level variability at the selected sites, showing that while local dynamics and the global signal modulate sea level to a given extent, most of the variance is driven by regional factors. On average, the MLR model is able to reproduce 82% of the variance in island sea level,
and could be used to derive local sea level projections via downscaling of climate models
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