The relation of wind stress curl and meridional transport in the Benguela upwelling system

Junker, Tim; Schmidt, Martin; Mohrholz, Volker

doi:10.1016/j.jmarsys.2014.10.006

Cited by 36 publications

(33 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…During this period, wind stress curl is at its maximum while alongshore wind stress is weak, coinciding with an offshore displacement of the zero‐wind stress curl contour. These results underline the importance of the precise cross‐shore wind structure for correctly simulating the EBC in upwelling regions that has been suggested previously (Fennel et al, ; Harlaß et al, , ; Junker et al, ; McCreary & Chao, ; Patricola & Chang, ; Small et al, ). Underneath the MC in the lCW layer, average flow was equatorward during both seasons.…”

Section: Resultssupporting

confidence: 81%

Seasonal Variability of the Mauritania Current and Hydrography at 18°N

2018

View full text Add to dashboard Cite

Extensive field campaigns in the Mauritanian upwelling region between 2005 and 2016 provide the database for analyzing the seasonal variability of the eastern boundary circulation (EBC) and associated water mass distribution at 18°N. The data set includes shipboard upper ocean current, hydrographic, and oxygen measurements from nine research cruises conducted during upwelling (December to April) and relaxation (May to July) seasons. During the upwelling season, the EBC closely resembles a classical eastern boundary current regime, with a poleward undercurrent flowing beneath an equatorward coastal jet. In contrast, elevated poleward flow exceeding 30 cm/s and extending from the surface down to 250‐m depth is observed during the relaxation season. The pronounced seasonal variability of the across‐shore structure of the EBC can be related to local wind forcing and is in general agreement with Sverdrup balance. The EBC transport is correlated to the wind stress curl leading the transport by 7 days. The short lead time suggests a fast response of locally forced waves adjusting the EBC to wind forcing. The seasonal and vertical water mass distribution is presented based on hydrographic observations. The meridional oxygen distribution and corresponding water mass partitioning into South and North Atlantic Central Water masses reveal a possible northerly ventilation pathway in the deeper layers of the central water stratum. Our results suggest that the poleward surface flow and the poleward undercurrent both are a consequence of the cyclonic wind stress curl forcing and thus propose to name it the Mauritania Current.

show abstract

Section: Resultssupporting

confidence: 81%

Seasonal Variability of the Mauritania Current and Hydrography at 18°N

2018

View full text Add to dashboard Cite

show abstract

Section: Resultsmentioning

confidence: 99%

“…Note that weaker (stronger) alongshore wind stress lead to warming (cooling) via reduced (increased) latent heat flux. Also, weak (strong) cyclonic wind stress curl could lead to a decrease (increase) of the poleward transport across the ABF (Junker et al, 2015). Figure 12f show that DNT10A in the ABF domain are influenced by CTW triggered in the Northern Namibia one month before the onset of the coastal event.…”

Section: 1029/2019jc015013mentioning

confidence: 97%

Benguela Niños and Benguela Niñas in Forced Ocean Simulation From 1958 to 2015

et al. 2019

View full text Add to dashboard Cite

A systematic study of Benguela Niño and Benguela Niña events during 1958 to 2015 including those that developed before the satellite era (1982) is carried out using an ocean general circulation model in combination with a linear equatorial model. Altogether, 21 strong warm and cold anomalous coastal events are identified among which 6 undocumented extreme coastal events are reported. Results suggest that most of these extreme coastal events including the newly identified ones are linked to remote equatorial forcing via mode 2 equatorial Kelvin waves. The latter propagates after approaching the African coast poleward as coastally trapped waves leading surface temperature anomalies along the Angola‐Benguela current system by one month. One to two months before the peak of Benguela Niños or Niñas usually occurring in March–April, a large‐scale wind stress forcing is observed with both local (variations of alongshore coastal wind stress) and remote forcing developing simultaneously. Results further suggest that surface temperature anomalies off Southern Angola and in the Angola‐Benguela Front are associated with equatorial dynamics and meridional wind stress fluctuations off the southwestern African coast north of 15°S. Similar mechanisms are observed for Northern Namibia in combination with forcing by local meridional wind stress variations.

show abstract

“…The origin of the Benguela Niño/Niña is still disputed by several studies. One possible mechanism is local wind forcing (e.g., [96,97]). According to this hypothesis, the Angola-Benguela Frontal Zone is maintained mainly by the tilting effect due to the upwelling and meridional confluence effect of the Angola and Benguela Currents (see Figure 1 of this manuscript; see also [10]).…”

Section: Benguela Niño/niñamentioning

confidence: 99%

Tropical Atlantic Variability: Observations and Modeling

2019

View full text Add to dashboard Cite

We review the state-of-the-art knowledge of Tropical Atlantic Variability (TAV). A well-developed observing system and sustained effort of the climate modeling community have improved our understanding of TAV. It is dominated by the seasonal cycle, for which some mechanisms have been identified. The interannual TAV presents a marked seasonality with three dominant modes: (i) the Atlantic Zonal Mode (AZM), (ii) the Atlantic Meridional Mode (AMM) and (iii) the variability in the Angola–Benguela Front (ABF). At longer time scales, the AMM is active and low-frequency variations in the strength, periodicity, and spatial structure of the AZM are observed. Also, changes in the mean position of the ABF occur. Climate models still show systematic biases in the simulated TAV. Their causes are model-dependent and relate to drawbacks in the physics of the models and to insufficient resolution of their atmospheric and oceanic components. The identified causes for the biases can have local or remote origin, involving the global ocean and atmospheric circulation. Although there is not a clear consensus regarding the role of model resolution in the representation of the TAV, eddy-resolving ocean models combined with atmospheric models with enhanced horizontal and vertical resolutions simulate smaller biases.

show abstract

The relation of wind stress curl and meridional transport in the Benguela upwelling system

Cited by 36 publications

References 23 publications

Seasonal Variability of the Mauritania Current and Hydrography at 18°N

Seasonal Variability of the Mauritania Current and Hydrography at 18°N

Benguela Niños and Benguela Niñas in Forced Ocean Simulation From 1958 to 2015

Tropical Atlantic Variability: Observations and Modeling

Contact Info

Product

Resources

About