Sea level anomalies using altimetry, model and tide gauges along the African coasts in the Eastern Tropical Atlantic Ocean: Inter-comparison and temporal variability

Dieng, H. B.; Dadou, Isabelle; Léger, Fabien; Morel, Yves; Jouanno, Julien; Lyard, Florent; Allain, Damien

doi:10.1016/j.asr.2019.10.019

Cited by 12 publications

(4 citation statements)

References 71 publications

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“…The altimetric sea surface height (SSH) and surface geostrophic currents used in this study are from the Salto/Duacs gridded product distributed by the Copernicus Marine Environment Monitoring Service (CMEMS), combining data from multiple satellite missions interpolated on a daily 0.25° grid (Le Traon et al, 1998;Ducet et al, 2000). The along-track coastal altimetry X-TRACK product with a 7-km and 10-day resolution (Birol et al, 2017) is also used and already validated using tide gauge data in the studied area (Dieng et al, 2019). For comparison, the respective model and altimetric SSH regionally averaged means are removed.…”

Section: Ancillary Datamentioning

confidence: 99%

Coastal Upwelling Limitation by Onshore Geostrophic Flow in the Gulf of Guinea Around the Niger River Plume

et al. 2021

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Wind-driven coastal upwelling can be compensated by onshore geostrophic flow, and river plumes are associated with such flow. We investigate possible limitation of the northeast Gulf of Guinea upwelling by the Niger River plume, using regional ocean model simulations with or without river and dynamical upwelling indices. Here, the upwelling is weakened by 50% due to an onshore geostrophic flow equally controlled by alongshore thermosteric and halosteric sea-level changes. The river contributes to only 20% of this flow, as its plume is shallow while upwelling affects coastal temperature and salinity over a larger depth. Moreover, the river-induced mixed-layer thinning compensates the current increase, with no net effect on upwelling. The geostrophic compensation is due to an abrupt change in coastline orientation that creates the upwelling cross-shore front. The river nonetheless warms the upwelling tongue by 1°C, probably due to induced changes in horizontal advection and/or stratification.

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Section: Ancillary Datamentioning

confidence: 99%

Coastal Upwelling Limitation by Onshore Geostrophic Flow in the Gulf of Guinea Around the Niger River Plume

et al. 2021

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“…Furthermore, the Equatorial Kelvin waves, induced either by zonal winds at the equator or through the reflection of equatorial or off-equatorial Rossby waves, propagate as CTW along the coast after reflecting at the western boundary. These signals can be measured by satellites, and their sea level signature provides sufficient information to identify them 19 , 51 – 54 . Over the past 20 years, interannual variability in ocean surface temperatures in the eastern equatorial Atlantic has been relatively low.…”

Section: Resultsmentioning

confidence: 99%

Sea level variability in Gulf of Guinea from satellite altimetry

Kemgang Ghomsi,

Raj,

Bonaduce

et al. 2024

Sci Rep

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Coastal zones with dense populations, low elevations and/or inadequate adaptive capacity are on the frontline of unprecedented impacts from climate change. The Gulf of Guinea (GoG), stretching from Liberia to Gabon, is in particular vulnerable to coastal flooding caused by local and/or climate-induced sea level rise. In this region, interannual to decadal coastal sea level changes remain poorly understood, mainly due to a lack of tide gauge stations. Here we use nearly three decades (1993–2021) of satellite altimetry data to study the link between the Equatorial Atlantic and coastal GoG sea level variability. The rate of mean sea level rise increased from 3.47 to 3.89 ± 0.10 mm/yr from the Equatorial oceanic domain to the GoG coastal area, with an acceleration of 0.094 ± 0.050 mm/yr2. This corresponds to a mean sea level rise of about 8.9 cm over the entire altimetry period, 1993–2021. We focus on the (extreme) warm/cold events that occur in both the GoG during Atlantic Niños, and along the Angola-Namibia coast during Benguela Niños. Both events are driven by remote forcing via equatorial Kelvin waves and local forcing by local winds, freshwater fluxes and currents intensifications. Analysis of altimetry-based sea level, sea surface temperature anomalies, 20 °C isotherm based PIRATA moorings, and the Argo-based steric and thermometric sea level allows us to follow the coastal trapped waves (CTWs) along the GoG, and its link with major events observed along the strong Equatorial Atlantic warmings in 2010, 2012, 2019 and 2021. Both 2019 and 2021 warming have been identified as the warmest event ever reported in this region during the last 40 years. A lag of 1 month is observed between equatorial and West African coastal trapped wave propagation. This observation may help to better anticipate and manage the effects of extreme events on local ecosystems, fisheries, and socio-economic activities along the affected coastlines. In order to enable informed decision-making and guarantee the resilience of coastal communities in the face of climate change, it emphasises the significance of ongoing study in this field.

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“…For example, Dieng et al. (2019) found approximately 4–5 cm of root‐mean‐square error (RMSE) for a gridded merged altimetry product at the African coast of the southeast tropical Atlantic. Marcello et al.…”

Section: Resultsmentioning

confidence: 99%

“…Evaluations of coastal altimetric SSH using tide-gauge observations showed discrepancies ranging from a few cm to tens of cm depending on the location. For example, Dieng et al (2019) found approximately 4-5 cm of root-mean-square error (RMSE) for a gridded merged altimetry product at the African coast of the southeast tropical Atlantic. Marcello et al (2021) reported about 4-12 cm of RMSE for SSH measurements from various altimeter missions at the Baltic coast.…”

Section: Impacts Of Nonseasonal Dischargementioning

confidence: 99%