Global observations of nonlinear mesoscale eddies
TL;DR: In this paper, an automated procedure for identifying and tracking mesoscale features based on their SSH signatures yields 35,891 eddies with average lifetime of 32 weeks and an average propagation distance of 550 km.
About: This article is published in Progress in Oceanography.The article was published on 2011-10-01. It has received 1744 citations till now. The article focuses on the topics: Baroclinity & Rossby wave.
Citations
More filters
TL;DR: The Lagrangian coherent structures (LCSs) as discussed by the authors are a skeleton of material surfaces, which can be used to shape the initial conditions of particle trajectories and frame, quantify, and forecast key aspects of material transport.
Abstract: Typical fluid particle trajectories are sensitive to changes in their initial conditions. This makes the assessment of flow models and observations from individual tracer samples unreliable. Behind complex and sensitive tracer patterns, however, there exists a robust skeleton of material surfaces, Lagrangian coherent structures (LCSs), shaping those patterns. Free from the uncertainties of single trajectories, LCSs frame, quantify, and even forecast key aspects of material transport. Several diagnostic quantities have been proposed to visualize LCSs. More recent mathematical approaches identify LCSs precisely through their impact on fluid deformation. This review focuses on the latter developments, illustrating their applications to geophysical fluid dynamics.
815 citations
TL;DR: The Canadian Earth System Model version 5 (CanESM5) as mentioned in this paper is a global model developed to simulate historical climate change and variability, to make centennial-scale projections of future climate, and to produce initialized seasonal and decadal predictions.
Abstract: . The Canadian Earth System Model version 5 (CanESM5) is a global
model developed to simulate historical climate change and variability, to
make centennial-scale projections of future climate, and to produce
initialized seasonal and decadal predictions. This paper describes the model
components and their coupling, as well as various aspects of model
development, including tuning, optimization, and a reproducibility strategy.
We also document the stability of the model using a long control simulation,
quantify the model's ability to reproduce large-scale features of the
historical climate, and evaluate the response of the model to external
forcing. CanESM5 is comprised of three-dimensional atmosphere (T63 spectral
resolution equivalent roughly to 2.8 ∘ ) and ocean (nominally 1 ∘ ) general
circulation models, a sea-ice model, a land surface scheme, and explicit
land and ocean carbon cycle models. The model features relatively coarse
resolution and high throughput, which facilitates the production of large
ensembles. CanESM5 has a notably higher equilibrium climate sensitivity
(5.6 K) than its predecessor, CanESM2 (3.7 K), which we briefly discuss, along
with simulated changes over the historical period. CanESM5 simulations
contribute to the Coupled Model Intercomparison Project phase 6 (CMIP6)
and will be employed for climate science and service applications in Canada.
509 citations
01 Jan 2001
TL;DR: Satellite altimetry is helping to advance studies of ocean circulation, tides, sea level, surface waves and allowing new insights into marine geodesy as mentioned in this paper, which is for a broad spectrum of academics, graduate students, and researchers in geophysics, oceanography, and the space and earth sciences.
Abstract: The new level of precision and global coverage provided by satellite altimetry is rapidly advancing studies of ocean circulation. It allows for new insights into marine geodesy, ice sheet movements, plate tectonics, and for the first time provides high-resolution bathymetry for previously unmapped regions of our watery planet and crucial information on the large-scale ocean features on intra-season to interannual time scales. Satellite Altimetry and Earth Sciences has integrated the expertise of the leading international researchers to demonstrate the techniques, missions, and accuracy of satellite altimetry, including altimeter measurements, orbit determination, and ocean circulation models. Satellite altimetry is helping to advance studies of ocean circulation, tides, sea level, surface waves and allowing new insights into marine geodesy. Satellite Altimetry and Earth Sciences provides high resolution bathymetry for previously unmapped regions of our watery planet. Satellite Altimetry and Earth Sciences is for a very broad spectrum of academics, graduate students, and researchers in geophysics, oceanography, and the space and earth sciences. International agencies that fund satellite-based research will also appreciate the handy reference on the applications of satellite altimetry.
443 citations
TL;DR: Large ocean eddies are the cause of some sea-surface height and chlorophyll anomalies previously ascribed to Rossby waves, and 10 years of measurements are analyzed to show that these eddies exert a strong influence on the CHL field, thus requiring reassessment of the mechanism for the observed covariability of SSH and CHL.
Abstract: Oceanic Rossby waves have been widely invoked as a mechanism for large-scale variability of chlorophyll (CHL) observed from satellites. High-resolution satellite altimeter measurements have recently revealed that sea-surface height (SSH) features previously interpreted as linear Rossby waves are nonlinear mesoscale coherent structures (referred to here as eddies). We analyze 10 years of measurements of these SSH fields and concurrent satellite measurements of upper-ocean CHL to show that these eddies exert a strong influence on the CHL field, thus requiring reassessment of the mechanism for the observed covariability of SSH and CHL. On time scales longer than 2 to 3 weeks, the dominant mechanism is shown to be eddy-induced horizontal advection of CHL by the rotational velocities of the eddies.
441 citations
TL;DR: In this article, a particle-trajectory tracer approach was used to study the fate of marine debris in the open ocean from coastal regions around the world on interannual to centennial timescales, finding that six major garbage patches emerged, one in each of the five subtropical basins and one previously unreported patch in the Barents Sea.
Abstract: Much of the debris in the near-surface ocean collects in so-called garbage patches where, due to convergence of the surface flow, the debris is trapped for decades to millennia. Until now, studies modelling the pathways of surface marine debris have not included release from coasts or factored in the possibilities that release concentrations vary with region or that pathways may include seasonal cycles. Here, we use observational data from the Global Drifter Program in a particle-trajectory tracer approach that includes the seasonal cycle to study the fate of marine debris in the open ocean from coastal regions around the world on interannual to centennial timescales. We find that six major garbage patches emerge, one in each of the five subtropical basins and one previously unreported patch in the Barents Sea. The evolution of each of the six patches is markedly different. With the exception of the North Pacific, all patches are much more dispersive than expected from linear ocean circulation theory, suggesting that on centennial timescales the different basins are much better connected than previously thought and that inter-ocean exchanges play a large role in the spreading of marine debris. This study suggests that, over multi-millennial timescales, a significant amount of the debris released outside of the North Atlantic will eventually end up in the North Pacific patch, the main attractor of global marine debris.
430 citations
References
More filters
Book•
14 Nov 2013
TL;DR: In this article, the authors describe how the Ocean-Atmosphere system is driven by transfer of properties between the atmosphere and the ocean. But they do not consider the effects of side boundaries.
Abstract: How the Ocean--Atmosphere System Is Driven. Transfer of Properties between Atmosphere and Ocean. Properties of a Fluid at Rest. Equations Satisfied by a Moving Fluid. Adjustment under Gravity in a Nonrotating System. Adjustment under Gravity of a Density-Stratified Fluid. Effect of Rotation. Gravity Waves in a Rotating Fluid. Forced Motion. Effects of Side Boundaries. The Tropics. Mid-Latitudes. Instabilities, Fronts, and the General Circulation. Units and Their SI Equivalents. Useful Values. Properties of Seawater. Properties of Moist Air. A List of Atlases and Data Sources. References. Index.
5,750 citations
Book•
01 Jan 1979
TL;DR: In this article, the authors propose a quasigeostrophic motion of a Stratified Fluid on a Sphere (SFL) on a sphere, which is based on an Inviscid Shallow-Water Theory.
Abstract: Preliminaries * Fundamentals * Inviscid Shallow-Water Theory * Friction and Viscous Flow * Homogeneous Models of the Wind-Driven Oceanic Circulation * Quasigeostrophic Motion of a Stratified Fluid on a Sphere * Instability Theory * Ageostrophic Motion
5,558 citations
TL;DR: Locally weighted regression as discussed by the authors is a way of estimating a regression surface through a multivariate smoothing procedure, fitting a function of the independent variables locally and in a moving fashion analogous to how a moving average is computed for a time series.
Abstract: Locally weighted regression, or loess, is a way of estimating a regression surface through a multivariate smoothing procedure, fitting a function of the independent variables locally and in a moving fashion analogous to how a moving average is computed for a time series With local fitting we can estimate a much wider class of regression surfaces than with the usual classes of parametric functions, such as polynomials The goal of this article is to show, through applications, how loess can be used for three purposes: data exploration, diagnostic checking of parametric models, and providing a nonparametric regression surface Along the way, the following methodology is introduced: (a) a multivariate smoothing procedure that is an extension of univariate locally weighted regression; (b) statistical procedures that are analogous to those used in the least-squares fitting of parametric functions; (c) several graphical methods that are useful tools for understanding loess estimates and checking the a
5,188 citations
TL;DR: In this paper, it was shown that two-dimensional turbulence has both kinetic energy and mean square vorticity as inviscid constants of motion, and two formal inertial ranges, E(k)∼e2/3k−5/3/3, where e is the rate of cascade of kinetic energy per unit mass, η is the time taken to reach a cascade of mean square velocity, and k is the kinetic energy of the entire mass.
Abstract: Two‐dimensional turbulence has both kinetic energy and mean‐square vorticity as inviscid constants of motion. Consequently it admits two formal inertial ranges, E(k)∼e2/3k−5/3 and E(k)∼η2/3k−3, where e is the rate of cascade of kinetic energy per unit mass, η is the rate of cascade of mean‐square vorticity, and the kinetic energy per unit mass is ∫0∞E(k) dk. The −53 range is found to entail backward energy cascade, from higher to lower wavenumbers k, together with zero‐vorticity flow. The −3 range gives an upward vorticity flow and zero‐energy flow. The paradox in these results is resolved by the irreducibly triangular nature of the elementary wavenumber interactions. The formal −3 range gives a nonlocal cascade and consequently must be modified by logarithmic factors. If energy is fed in at a constant rate to a band of wavenumbers ∼ki and the Reynolds number is large, it is conjectured that a quasi‐steady‐state results with a −53 range for k « ki and a −3 range for k » ki, up to the viscous cutoff. The t...
2,950 citations
"Global observations of nonlinear me..." refers background in this paper
...…by ridges and valleys that are part of the overall mesoscale variability, presumably arising from the spectral continuum of the up-scale energy cascade of geostrophic turbulence (e.g., Kraichnan, 1967; Batchelor, 1969; Charney, 1971; Rhines, 1979; Stammer, 1997; Scott and Wang, 2005, and others)....
[...]