North Atlantic Barotropic Vorticity Balances in Numerical Models

Schoonover, Joseph; Dewar, William K.; Wienders, N.; Gula, Jonathan; McWilliams, James C.; Molemaker, M. Jeroen; Bates, S. C.; Danabasoglu, Gökhan; Yeager, Stephen

doi:10.1175/jpo-d-15-0133.1

Cited by 31 publications

(101 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The sink of mesoscale energy to the atmosphere is naturally ignored in uncoupled WBC model simulations. These simulations suffer from two enduring biases concerning WBC patterns: AC retroflection and GS separation and penetration into the North Atlantic basin (Loveday et al, ; Schoonover et al, ; Renault, Molemaker, Gula, et al, ; Renault, McWilliams, Penven, et al, ). Eddy killing was shown to control essential characteristics of these features, partially correcting model biases.…”

Section: Resultsmentioning

confidence: 99%

Remarkable Control of Western Boundary Currents by Eddy Killing, a Mechanical Air‐Sea Coupling Process

Renault

Marchesiello

Masson

et al. 2019

Geophysical Research Letters

View full text Add to dashboard Cite

Western boundary currents (WBCs) are critical to Earth's climate. In the last decade, mesoscale air‐sea interactions emerged as an important factor of WBC dynamics. Recently, coupled models including the feedback of surface oceanic currents to the atmosphere confirmed the existence of a physical process called eddy killing, which may correct long‐lasting biases in the representation of WBCs by providing an unambiguous energy sink mechanism. Using ocean‐atmosphere coupled simulations of the Gulf Stream and the Agulhas Current, we show that eddy killing reduces the eddy‐mean flow interaction (both forward and inverse cascades) and leads to more realistic solutions. Model and data fluxes are in good agreement when the same coarse grid is used for their computation, although in this case they are underestimated. We conclude that the uncoupled approach is no longer suitable for continued ocean model improvement and discuss new formulations that should better account for air‐sea interactions.

show abstract

Section: Resultsmentioning

confidence: 99%

Remarkable Control of Western Boundary Currents by Eddy Killing, a Mechanical Air‐Sea Coupling Process

Renault

Marchesiello

Masson

et al. 2019

Geophysical Research Letters

View full text Add to dashboard Cite

show abstract

“…In particular, the biases in the surface storm tracks, as compared to the biases in the free-tropospheric storm tracks, may inform on model issues regarding the WBCs and the modeled momentum mixing in the midlatitudes. It is already known that GCMs often have issues in representing the separation of the WBCs from the coastlines in the Northern Hemisphere, in particular, for the non-eddyresolving ocean models (e.g., Gent et al 2011;Schoonover et al 2016). Coupled models with eddyresolving oceans better represent the strength, width, and path of the WBCs, but can still exhibit overshooting of the path (e.g., Small et al 2014;Griffies et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Spatial Patterns and Intensity of the Surface Storm Tracks in CMIP5 Models

Booth

Kwon

et al. 2017

J. Climate

View full text Add to dashboard Cite

To improve the understanding of storm tracks and western boundary current (WBC) interactions, surface storm tracks in 12 CMIP5 models are examined against ERA-Interim. All models capture an equatorward displacement toward the WBCs in the locations of the surface storm tracks' maxima relative to those at 850 hPa. An estimated storm-track metric is developed to analyze the location of the surface storm track. It shows that the equatorward shift is influenced by both the lower-tropospheric instability and the baroclinicity. Basin-scale spatial correlations between models and ERA-Interim for the storm tracks, near-surface stability, SST gradient, and baroclinicity are calculated to test the ability of the GCMs' match reanalysis. An intermodel comparison of the spatial correlations suggests that differences (relative to ERA-Interim) in the position of the storm track aloft have the strongest influence on differences in the surface storm-track position. However, in the North Atlantic, biases in the surface storm track north of the Gulf Stream are related to biases in the SST. An analysis of the strength of the storm tracks shows that most models generate a weaker storm track at the surface than 850 hPa, consistent with observations, although some outliers are found. A linear relationship exists among the models between storm-track amplitudes at 500 and 850 hPa, but not between 850 hPa and the surface. In total, the work reveals a dual role in forcing the surface storm track from aloft and from the ocean surface in CMIP5 models, with the atmosphere having the larger relative influence.

show abstract

“…Hughes and de Cuevas, 2001;Lu and Stammer, 2004;Jackson et al, 2006;Schoonover et al, 2015;Yeager, 2015). We can derive an equation that is analogous to the barotropic vorticity equation by taking the contour integral of equation 2.5 before dividing it by h. While the barotropic vorticity equation in Hughes and de Cuevas (2001) is based on an integral over the full water column, here we integrate from the isopycnal at = −ℎ( , , ) to the surface so that the result is comparable to our equation 2.9.…”

Section: Mathematical Connection To Depth-integrated Vorticity Frameworkmentioning

confidence: 84%

“…There is an appreciation for all of these developments in the recent literature, and ad-vances in modeling the ocean have enabled the detailed diagnosis of PV transformations in ocean models (Czaja and Hausmann, 2009;Deremble et al, 2014;Yeager, 2015;Schoonover et al, 2015). However, the connection between the classical balances of Stommel and Munk and the detailed PV maps in ocean models is not straightforward, with the interpretation of the dynamical balance depending on the mathematical framework (Jackson et al, 2006).…”

Section: Scientific Contextmentioning

confidence: 99%

See 1 more Smart Citation

Dynamics of North Atlantic western boundary currents

Bras¹,

Isabela²

2017

View full text Add to dashboard Cite

The Gulf Stream and Deep Western Boundary Current (DWBC) shape the distribution of heat and carbon in the North Atlantic, with consequences for global climate. This thesis employs a combination of theory, observations and models to probe the dynamics of these two western boundary currents.First, to diagnose the dynamical balance of the Gulf Stream, a depth-averaged vorticity budget framework is developed. This framework is applied to observations and a state estimate in the subtropical North Atlantic. Budget terms indicate a primary balance of vorticity between wind stress forcing and dissipation, and that the Gulf Stream has a significant inertial component.The next chapter weighs in on an ongoing debate over how the deep ocean is filled with water from high latitude sources. Measurements of the DWBC at Line W, on the continental slope southeast of New England, reveal water mass changes that are consistent with changes in the Labrador Sea, one of the sources of deep water thousands of kilometers upstream. Coherent patterns of change are also found along the path of the DWBC. These changes are consistent with an advective-diffusive model, which is used to quantify transit time distributions between the Labrador Sea and Line W. Advection and stirring are both found to play leading order roles in the propagation of water mass anomalies in the DWBC.The final study brings the two currents together in a quasi-geostrophic process model, focusing on the interaction between the Gulf Stream's northern recirculation gyre and the continental slope along which the DWBC travels. We demonstrate that the continental slope restricts the extent of the recirculation gyre and alters its forcing mechanisms. The recirculation gyre can also merge with the DWBC at depth, and its adjustment is associated with eddy fluxes that stir the DWBC with the interior. This thesis provides a quantitative description of the structure of the overturning circulation in the western North Atlantic, which is an important step towards understanding its role in the climate system.

show abstract

North Atlantic Barotropic Vorticity Balances in Numerical Models

Cited by 31 publications

References 32 publications

Remarkable Control of Western Boundary Currents by Eddy Killing, a Mechanical Air‐Sea Coupling Process

Remarkable Control of Western Boundary Currents by Eddy Killing, a Mechanical Air‐Sea Coupling Process

Spatial Patterns and Intensity of the Surface Storm Tracks in CMIP5 Models

Dynamics of North Atlantic western boundary currents

Contact Info

Product

Resources

About