Evaluating two numerical advection schemes in HYCOM for eddy-resolving modelling of the Agulhas Current

Backeberg, Björn; Bertino, Laurent; Johannessen, Johnny A.

doi:10.5194/os-5-173-2009

Cited by 24 publications

(23 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…According to Biastoch et al (2009), the retroflection occurs at 178E during shedding and 238E (i.e., east from the Agulhas Bank) afterward. Similar scenarios can be seen in the Backeberg et al (2009) and Tsugawa and Hasumi (2010) simulations.…”

Section: B Numerical Backgroundsupporting

confidence: 76%

A New Model of Current Retroflection Applied to the Westward Protrusion of the Agulhas Current

Arruda

Zharkov

Deremble

et al. 2014

Journal of Physical Oceanography

View full text Add to dashboard Cite

The dynamics of current retroflection and rings shedding are not yet fully understood. In this paper, the authors develop an analytical model of the Agulhas Current retroflection dynamics using three simple laws: conservation of volume, momentum balance, and Bernoulli's principle. This study shows that, for a retroflecting current with a small Rossby number, this theoretical model is in good agreement with numerical simulations of a reducedgravity isopycnal model. Otherwise, the retroflection position becomes unstable and quickly propagates upstream, leaving a chain of eddies in its path. On the basis of these findings, the authors hypothesize that the westward protrusion of the Agulhas retroflection and the local ''zonalization'' of the Agulhas Current after it passes the Agulhas Bank are stable only for small Rossby numbers. Otherwise, the retroflection shifts toward the eastern slope of the Agulhas Bank, where its position stabilizes due to the slanted configuration of the slope. This study shows that this scenario is in good agreement with several high-resolution numerical models.

show abstract

Section: B Numerical Backgroundsupporting

confidence: 76%

A New Model of Current Retroflection Applied to the Westward Protrusion of the Agulhas Current

Arruda

Zharkov

Deremble

et al. 2014

Journal of Physical Oceanography

View full text Add to dashboard Cite

show abstract

“…This results in an average retroflection position at 23 • E in the model, which is 5 • too far east. The same behavior of the AC was seen in a 0.1 • horizontal resolution regional configuration of the Hybrid Coordinate Ocean Model (HYCOM) and was greatly improved by replacing the 2nd order momentum advection scheme by a 4th order scheme (Backeberg et al, 2009). The 2nd order momentum advection scheme of POP could then be responsible for the early retroflection of the AC.…”

Section: Agulhas Retroflectionmentioning

confidence: 68%

Impact of the Indonesian Throughflow on Agulhas leakage

2013

View full text Add to dashboard Cite

Abstract. Using ocean models of different complexity we show that opening the Indonesian Passage between the Pacific and the Indian oceans increases the input of Indian Ocean water into the South Atlantic via the Agulhas leakage. In a strongly eddying global ocean model this response results from an increased Agulhas Current transport and a constant proportion of Agulhas retroflection south of Africa. The leakage increases through an increased frequency of ring shedding events. In an idealized two-layer and flat-bottom eddy resolving model, the proportion of the Agulhas Current transport that retroflects is (for a wide range of wind stress forcing) not affected by an opening of the Indonesian Passage. Using a comparison with a linear model and previous work on the retroflection problem, the result is explained as a balance between two mechanisms: decrease retroflection due to large-scale momentum balance and increase due to local barotropic/baroclinic instabilities.

show abstract

“…The peaks here are related to the formation of barotropic Agulhas rings in the model. Too regular ring formation is a shortcoming that many numerical ocean models of the region share [ Lutjeharms and Webb , ; Backeberg et al ., ]. Nevertheless, the frequency of ring formation is, with about five rings shed per year, in accordance with estimates from the literature [ van Aken et al ., ].…”

Section: Resultsmentioning

confidence: 99%

Ocean bottom pressure signals around Southern Africa from in situ measurements, satellite data, and modeling

Kuhlmann

Dobslaw

Petrick

et al. 2013

J. Geophys. Res. Oceans

View full text Add to dashboard Cite

[1] Ocean bottom pressure (OBP) variability in the region of the Agulhas Current off the South African coast is a crucial variable in the understanding of dynamic processes in the ocean, but measurements currently available lack either precision or spatial and temporal coverage. We provide a quantitative estimate of OBP variability throughout the region with the help of a setup of the ROMS regional ocean model. Driving the model with boundary conditions from a global ocean model and atmospheric reanalysis data and running it for 8 years, we are able to reproduce many characteristic properties of the regional ocean circulation visible in sea surface height and OBP fields. While the in situ pressure-inverted echo sounders (PIES) measuring local OBP variations on short time scales are sparse in the region, our model provides a comprehensive estimate of OBP variations throughout the region which reach values of up to 15 hPa when barotropic Agulhas rings reach the Cape Basin. These signals turn out to be difficult to measure with current gravimetry solutions from the GRACE satellites, but estimates of localized noise levels for a GRACE follow-on mission let the search for them in future satellite measurements appear viable.Citation: Kuhlmann, J., H. Dobslaw, C. Petrick, and M. Thomas (2013), Ocean bottom pressure signals around Southern Africa from in situ measurements, satellite data, and modeling,

show abstract

Evaluating two numerical advection schemes in HYCOM for eddy-resolving modelling of the Agulhas Current

Cited by 24 publications

References 42 publications

A New Model of Current Retroflection Applied to the Westward Protrusion of the Agulhas Current

A New Model of Current Retroflection Applied to the Westward Protrusion of the Agulhas Current

Impact of the Indonesian Throughflow on Agulhas leakage

Ocean bottom pressure signals around Southern Africa from in situ measurements, satellite data, and modeling

Contact Info

Product

Resources

About