Relevant ocean processes include upper and deep ocean circulation, eddies, tropical instability waves, mixing, and upwellings. For air-sea interactions, we welcome studies analyzing the seasonal cycle, marine heat waves, the development of variability modes on local to basin scale (e.g., Atlantic, Dakar and Benguela Niños, Atlantic Meridional Mode and South Atlantic Ocean Dipole) and interbasin teleconnections. Wind variations related to high-frequency events, cyclones, convective systems and those shaping air-sea coupled modes are encouraged.
Finally, we seek for studies that explore the causes and impacts of systematic model errors in simulating the local to regional Atlantic climate variability. Submissions based on direct observations, reanalysis, model simulations and machine learning techniques are welcome.
Orals: Tue, 5 May, 16:15–18:00 | Room L2
The tropical Atlantic Ocean is characterized by energetic mean currents, pronounced equatorial wave activity, and enhanced seasonal upper-ocean instability. Variability and extreme events in this region exert a strong influence on weather and climate over adjacent continents and contribute to atmospheric teleconnections with the other tropical ocean basins. Despite this importance, sustained observations of equatorial Atlantic Ocean dynamics remain limited.
To address this gap, a moored observatory has been operated at 0°, 23°W since December 2001, with evolving configurations. In its current design the observatory consists of a subsurface mooring equipped with Acoustic Doppler Current Profilers measuring velocities in the upper 900 m and a McLane Moored Profiler sampling the 900-3,300 m depth range. Additional single-point current meters are deployed at variable depths. These time series are combined with current meter measurements from the nearby PIRATA moored surface buoy and with full-depth shipboard velocity profiles collected during regular French and U.S. PIRATA mooring service cruises.
In this presentation, we provide updated perspectives and new results on the structure, variability and trends of the zonal and meridional velocity components of the equatorial Atlantic circulation. For instance, in the upper ocean, the eastward Equatorial Undercurrent (EUC) exhibits a marked decline in volume transport since 2018, following a decade of strengthening transport and enhanced oxygen ventilation of the eastern equatorial Atlantic between 2008 and 2018. Consistent with this decadal variability, the mean core depth of the EUC has shoaled by approximately 10 m relative to 2018.
Variability in the meridional velocity component is dominated by intraseasonal time scales (~10-50 days), reflecting the presence of tropical instability waves (TIWs) in the upper 100 m, and equatorial Yanai waves at greater depths. While observations suggest an apparent increase in TIW activity, which are on average most pronounced from July to September, a detailed seasonal analysis indicates that the inferred long-term trends largely arise from a systematic shift toward an earlier onset of TIW activity rather than from a sustained intensification.
Since 2022, a combined full-depth velocity product has been released shortly after each mooring recovery (Tuchen et al., 2022). Maintaining long-term observations such as the equatorial moored observatory at 23°W is logistically and financially demanding, but remains essential for detecting and interpreting decadal variability and long-term trends in the tropical Atlantic.
Tuchen, F. P., Brandt, P., Hahn, J., Hummels, R., Krahmann, G., Bourlès, B., Provost, C., McPhaden, M. J., and Toole, J. M. (2022): Two Decades of Full-Depth Current Velocity Observations From a Moored Observatory in the Central Equatorial Atlantic at 0°N, 23°W. Front. Mar. Sci. 9:910979. https://doi.org/10.3389/fmars.2022.910979
How to cite: Tuchen, F. P., Brandt, P., and Hummels, R.: Equatorial Atlantic Ocean dynamics across time scales from sustained velocity observations between 2001-2025, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5468, https://doi.org/10.5194/egusphere-egu26-5468, 2026.
The North Atlantic exhibits pronounced variability on decadal to multidecadal timescales, commonly referred to as Atlantic Multidecadal Variability (AMV). AMV has been linked to climate variability in many regions across the globe. Modelling studies indicate that the global teleconnections of AMV are sensitive to how the tropical branch is represented, though understanding the processes governing its development has received little attention. Moreover, coupled climate models show substantial diversity in simulating the tropical arm of AMV, yet the mechanisms responsible for this inter-model spread remain poorly understood. Here we show that tropical AMV exhibits a seasonal cycle in observations, with growth during boreal summer and decay during boreal winter. Coupled models differ markedly in their ability to capture this observed seasonality. Models that reproduce the observed seasonal evolution of tropical AMV provide insight into its underlying dynamics, revealing that variations in latent heat flux, shortwave radiation, and mixed-layer depth driven by changes in the trade winds are central to the growth and decay of tropical AMV. In contrast, models that fail to represent trade wind weakening and associated ocean-atmosphere interaction processes exhibit substantial deficiencies in simulating tropical AMV. Consequently, models that correctly capture the observed seasonality of tropical AMV also reproduce its associated climate impacts, including variability in Sahel rainfall and the Indian summer monsoon, whereas models that do not capture this seasonality fail to simulate these impacts properly. Given the sensitivity of global climate to tropical AMV, these results highlight the importance of accurately representing the processes linking the extratropical North Atlantic and tropical ocean-atmosphere interactions in coupled climate models.
How to cite: Senapati, B., O’Reilly, C. H., and Robson, J.: Mechanisms of Internal Tropical Atlantic Multidecadal Variability: Seasonality, Model Diversity, and Climate Impacts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8406, https://doi.org/10.5194/egusphere-egu26-8406, 2026.
Tropical north Atlantic sea surface temperature anomalies (TNA SSTAs) have far-reaching climate impacts both locally and remotely. For the first time, this study reveals pronounced multidecadal variations in the seasonal persistence of spring TNA SSTAs, which is relatively higher at the early and late 20th century but significantly lower during the middle 20th century. Contrast to the nonstationary El Niño-Southern Oscillation (ENSO)-TNA connection, these fluctuations in TNA SSTA seasonal persistence are mainly linked to multidecadal shifts in the North Atlantic Oscillation (NAO)-TNA connection. Specifically, the asymmetric impacts of extreme NAO events drive both multidecadal fluctuations in the TNA SSTA seasonal persistence and shifts of NAO-TNA connection. The asymmetric impacts of extreme NAO events are enhanced in historical periods by external forcings and is projected to amplify further under further climate conditions.
How to cite: Yan, X.: Multidecadal variations of the persistence of Tropical North Atlantic sea surface temperature, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4717, https://doi.org/10.5194/egusphere-egu26-4717, 2026.
Atmospheric cold pools are transient sub-mesoscale to mesoscale weather phenomena generated by convective precipitation. They are characterized by cool, dense air spreading laterally, which strongly alters near-surface atmospheric conditions and the thermohaline properties of the ocean skin layer (< 1 mm) and near-surface layer (NSL: < 1 m). The spatial extent and thermodynamic intensity of atmospheric cold pools are moderated by mixing within the moist marine boundary layer (MBL), the lowest ~0.5–1 km of air above the ocean. Despite this moderation, accompanying wind surges and intense precipitation drive short-lived intensifications of atmosphere–ocean fluxes that can abruptly restructure upper-ocean thermohaline structure, an aspect that remains poorly constrained by in situ measurements and is underrepresented in coupled atmosphere–ocean models.
Here we present observations of atmospheric cold pool passages over the tropical Atlantic Ocean, combining ship-based meteorological measurements, aerial drones, weather balloon profiles, and high-resolution observations from the autonomous surface vehicle HALOBATES. Equipped with meteorological and oceanographic sensors sampling at high-resolution (1 Hz), HALOBATES resolves the ocean skin layer and the NSL dynamics, allowing us to identify and characterize cold pools as they passed over the study area during the R/V METEOR M211 field campaign (14 June–27 July 2025).
Between 13 and 18 July 2025, cold pool passages were identified by rapid air-temperature drops of 0.6–1.8 °C and, during rainy events, rainfall rates of up to 37 mm h⁻¹. All cold pools induced transient ocean surface cooling, leading to sea surface temperature anomalies (Tskin-TNSL) of 0.02 – 0.35 °C, and amplified cooling in the skin layer relative to the NSL. To quantify the cooling and recovery of the ocean skin layer following the cold pool passage, we consider two different skin-layer depths: the infrared (IR) skin layer observed by thermal cameras and the skin layer measured in situ by HALOBATES. This comparison shows that skin-temperature responses evolve on timescales of only a few minutes and therefore require high temporal resolution in situ measurements to be adequately resolved.
Salinity responses depended critically on precipitation: cold pools that passed the study area without measurable rainfall produced negligible changes, whereas intense-rain events freshened the skin by up to 1.3 g kg-1 and the NSL by 0.4 g kg-1, forming shallow freshwater lenses that re-stratified the upper meter within approximately 15 minutes. Pronounced cold pool passages were accompanied by enhanced latent and sensible heat fluxes, with maximum increases of −140 W m⁻² and −30 W m⁻², respectively, driven primarily by increased wind speeds and indicating intensified ocean-to-atmosphere heat exchange. These observations demonstrate that cold pools strongly affect short-term variability in upper-ocean thermohaline structure through short-lived intense peaks in atmosphere–ocean fluxes, emphasizing the need to include these transient events in future coupled atmosphere–ocean models.
How to cite: Bibi, R., Jaeger, L., Rauch, C., Mintah Ayim, S., Gassen, L., Ribas-Ribas, M., W. Freeman, S., Britton, K., D. Grant, L., M. Falk, N., A. Neumaier, C., van den Heever, S., L. Monroy, D., Härter, J., and Wurl, O.: Cold Pools Drive Short-Term Thermohaline Variability in the Ocean Skin Layer, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14270, https://doi.org/10.5194/egusphere-egu26-14270, 2026.
The influence of equatorial Atlantic SST on the El Niño Southern Oscillation (ENSO) has remained robust over the 40 years, despite the strong weakening of Atlantic Niño variability post 2000. To investigate the nature of these interactions through pacemaker experiments with the Norwegian Earth System Model (NorESM). In these experiments tropical Atlantic sea surface temperatures (SST) are restored to observations over the period 1980 to 2020. We perform two experiments, one with long-term warming included and one with it removed linearly. Each experiment consists of 20 ensemble members, sampling internal variability, model uncertainty (NorESM1/NorESM2), and nudging approach (anomaly vs full field restoring). Our results show first that equatorial Atlantic SST variations in the west determine the impact on the ENSO, rather than those in the east. And second, that the long-term warming of the tropical Atlantic SST has opposed this interaction. While the first effect has maintained the robust connection during the last 40 years, we expect the second effect to dominate in the long-term, leading to weaker Atlantic Niño impacts on the Pacific.
How to cite: Chiu, P.-G. and Keenlyside, N.: Disentangling equatorial Atlantic’s influence on ENSO since 1980, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22469, https://doi.org/10.5194/egusphere-egu26-22469, 2026.
El Niño–Southern Oscillation (ENSO) is a major driver of climate variability in the North Atlantic through atmospheric teleconnections that influence circulation patterns and climate conditions across the Euro-Atlantic region. These teleconnections constitute an important source of interannual climate variability and predictability. Previous studies suggest that, under greenhouse-warming scenarios, ENSO teleconnections to the North Atlantic are likely to intensify, largely as a result of changes in the mean climate state and projected modifications in ENSO characteristics.
In this study, we show that changes in ENSO–North Atlantic teleconnections under global warming have significant implications for seasonal climate predictability over Europe. Our results show that a strengthening and reorganization of these teleconnections alters the robustness and spatial coherence of ENSO-related climate signals, thereby directly influencing predictability in the Euro-Atlantic sector.
In addition, we explore the potential role of the Tropical North Atlantic as a modulator of ENSO teleconnections to Europe. Previous studies suggest that variability in Tropical North Atlantic sea surface temperatures can influence the atmospheric response to ENSO, potentially modifying its impact on the North Atlantic and European climate. Our results support the idea that the Tropical North Atlantic may play an important role in shaping ENSO-related climate signals and their predictability.
How to cite: Santuy Muñoz, D., Polo Sánchez, I., and Rodríguez Fonseca, B.: ENSO teleconnection to the North Atlantic under greenhouse warming and its modulation by the Tropical North Atlantic, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12276, https://doi.org/10.5194/egusphere-egu26-12276, 2026.
El Niño-Southern Oscillation (ENSO) affects weather and climate around the world but its impact on the equatorial Atlantic has been surprisingly inconsistent, with some major El Niño events followed by cooling in the equatorial Atlantic, while others were followed by warming. Here we use climate change projections from the Coupled Model Intercomparison Project Phase 6 (CMIP6) to examine how ENSO’s relation with the equatorial Atlantic may change under global warming.
Similar to ENSO, variability in the equatorial Atlantic, also known as the Atlantic Zonal Mode (AZM), is influenced by the Bjerknes feedback, in which sea-surface temperature (SST) anomalies drive deep convection and a surface wind response that amplifies the original SST anomalies. Due to the stabilization of the atmosphere under global warming, this Atlantic feedback weakens in the CMIP6 projections. Instead, many models suggest a scenario in which the AZM is dominantly driven by ENSO’s thermodynamic forcing, namely the tropics-wide tropospheric warming (cooling) that follows El Niño (La Niña) events. As a result, ocean dynamics and coupled air-sea feedbacks play a much weaker role, while ENSO’s influence on the AZM becomes more consistent. Analysis with a simple linear prediction scheme suggests that this can also increase the predictability of the AZM, due to the high predictability of ENSO.
While many models envision an ENSO-dominated future, some continue to simulate an independent, dynamically driven AZM until the end of the 21st century. The potential reasons for this disparate behavior will be discussed.
How to cite: Richter, I., Chang, P., Kataoka, T., Kido, S., Noel, K., Kosaka, Y., Okumura, Y., Tokinaga, H., Tozuka, T., and Vilela, I.: Changes in the ENSO-AZM connection under global warming, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15698, https://doi.org/10.5194/egusphere-egu26-15698, 2026.
The Pacific ENSO and the Atlantic Niño/Niña change oppositely in the 21st century. Here, we find the weakened Atlantic Meridional Overturning Circulation (AMOC) plays a key role. Via reducing the equatorial Pacific trades and the Atlantic poleward heat transport, the weakened AMOC contributes to, at surface, a similar Niño-like sea surface temperature (SST) warming and a strengthened atmospheric stratification in both basins, while, at subsurface, a western Pacific cooling in comparison to an intense Atlantic warming. The distinct subsurface changes induce strengthened Pacific oceanic stratification to enhance Bjerknes feedback, in contrast to an insignificant change in the Atlantic. Moreover, the similar surface changes exert different impacts, with a strengthened atmospheric stratification suppressing the Atlantic Bjerknes feedback, an influence offset in the Pacific by an eastward shift of deep convection due to Niño-like SST warming. Such offset is absent in the Atlantic owing to the northern-hemisphere-located deep convection.
How to cite: Yang, Y., Wu, L., Cai, W., Cheng, X., Mei, X., Jia, F., Li, S., Geng, T., Chen, Y., and Wang, H.: Weakened Atlantic Meridional Overturning Circulation Contributes to Opposite Responses of ENSO and the Atlantic Niño/Niña to Greenhouse Warming, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2395, https://doi.org/10.5194/egusphere-egu26-2395, 2026.
The Benguela Niño/Niña events manifest the anomalous signals of sea surface temperature (SST) in the upwelling region off the west coast of Africa. These events are triggered by the interannual modulation of either equatorial waves or local atmospheric forcing. In the present study, the mechanism that equatorial waves induce the coastal SST anomaly is investigated in terms of the transfer episodes of wave energy by both numerical experiments and reanalysis data. The result of numerical experiments suggests that most of the coastal events can be reproduced by subseasonal wind forcing with an interannual modulation that excites oceanic waves of the first three baroclinic modes. The transfer routes of wave energy illustrate the role of wave dynamics that explains how the interannual variability of SST in the equatorial Atlantic is connected with that in coastal regions. The linearly superposed sign-indefinite potential energy flux owing to waves manifests its capability of sufficiently displacing the thermocline so as to trigger the coastal events. The diagnosis of wave energy for reanalysis data further confirms that there are clear wave energy routes from the equatorial Atlantic to the coastal region, along which different source regions for waves in the first-four modes are found, jointly contributing to the 2019 Niño event.
How to cite: Song, Q., Tang, Y., and Aiki, H.: The Role of Equatorially Forced Waves in Triggering Benguela Niño/Niña as Investigated by an Energy Flux Diagnosis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18445, https://doi.org/10.5194/egusphere-egu26-18445, 2026.
Upwelling processes bring nutrient-rich waters from the deep ocean to the surface. Areas of upwelling are often associated with high productivity, offering great economic value in terms of fisheries. Thus, predictive skill for regional oceanographic conditions is highly desirable. On this aspect, we analyzed the seasonal prediction of the marine ecosystem drivers such as the net primary production and phytoplankton biomass along the Senegalo-Mauritanian and Moroccan upwelling systems, using the latest version of the German Climate Forecast System GCFS2.2. Our results generally show that the Senegalo-Mauritanian upwelling system is predictable 1 to 4 months in advance during boreal winter, consistent with the sea surface temperature and wind forcing (physical variables). On the other hand, in the Morocco system the effective predictability horizon for the marine ecosystem drivers extends up to 4 months, whereas that for the physical variables hardly reaches one month. Our results highlight the different mechanisms and properties impacting the different predictability horizon one can expect in the Senegalo-Mauritanian and Moroccan upwelling systems.
How to cite: Sylla, A., Brune, S., Capet, X., Mignot, J., and Baehr, J.: Mechanisms and seasonal marine biochemical prediction over the Canary upwelling system using the German Climate Forecast System GCFS2.2, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7349, https://doi.org/10.5194/egusphere-egu26-7349, 2026.
Posters on site: Tue, 5 May, 10:45–12:30 | Hall X4
The western equatorial Atlantic Ocean features a variety of dynamical processes. The upper-ocean circulation is characterized by both western boundary currents and the equatorial current system, which are important pathways of the upper branch of the Atlantic Meridional Overturning Circulation (AMOC). On subseasonal to seasonal timescales, equatorial waves further influence local ocean dynamics. Yanai waves (sometimes referred to as mixed Rossby-gravity waves) are observed in all tropical ocean basins on timescales of 10 to 30 days. They are associated with meridional velocities at the equator, setting them apart from other equatorial waves. While Yanai waves have been thoroughly analyzed regarding their energy dissipation, generation mechanisms, and propagation characteristics, little observational evidence has been provided regarding their surface trajectories. This study investigates the trajectories of Lagrangian surface drifters with respect to the presence of Yanai waves. Only few surface drifters remain long enough at or close to the equator to offer insights into equatorial phenomena since the prevailing poleward Ekman flow near the equator typically drives drifters to higher latitudes fairly quickly which makes measurements difficult, but valuable. During a research cruise in May 2023, 8 surface drifters were deployed into the western boundary current system off Brazil along 35°W between the equator and 2.25°S. Three of these drifters became trapped within circling surface velocities centered around the equator which can be attributed to a Yanai wave. One commonly accepted generation mechanism of Yanai waves in the ocean is cross-equatorial fluctuation of the meridional velocity component of the wind. Evidence for fluctuations at the same period as the drifters oscillations was detected in current velocities driven by wind fluctuations. By conducting a series of numerical experiments with artificial drifters, combining the mean background flow of the area with theoretical Yanai wave-induced surface velocities, the observed trajectories can be reproduced. The Yanai wave is characterized by a 14-day period and velocity amplitudes of approximately 0.6 to 0.7 m/s.
How to cite: Andrae, A., Brandt, P., Hummels, R., Tuchen, F. P., and Lübbecke, J.: Observed Yanai wave trajectories in the Equatorial Atlantic Ocean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1940, https://doi.org/10.5194/egusphere-egu26-1940, 2026.
Boreal spring and summer tropical Atlantic variability is governed by the Atlantic Meridional Mode (AMM) and Atlantic Zonal Mode (AZM) at interannual timescales. Previous studies have identified a connection between AMM and AZM through ocean wave propagation and local wind forcing (Foltz and McPhaden 2010; Burmeister et al. 2016; Martín-Rey and Lazar 2019; Martín-Rey et 2023). For a positive phase of the AMM, anomalous negative wind curl north of the equator triggers a downwelling Rossby wave that propagates westward and is boundary-reflected into an equatorial Kelvin wave (KW). This dKW travels along the equator during summer months, activating the oceanic processes responsible to warm the sea surface, thus favouring the development of a positive AZM. However, the existence of anomalous local zonal winds could modulate the impact of the dKW, and consequently, the phase of the AZM following the AMM (Martín-Rey and Lazar 2019; Martín-Rey et al. 2023).
Here, we use the Maximum-Covariance based Python statistical tool Spy4Cast to explore the existence of a AMM-AZM connection, as well as, the relative role of each precursor (local wind vs oceanic waves). Spy4cast (Durán-Fonseca and Rodríguez-Fonseca 2025) allows for identifying coupled modes of variability as well as to produce statistical predictions. In this way the AZM predictability will be assessed together with the stability of the connection. Thus, the non-stationary behaviour of this connection will be evaluated, as well as the favourable background conditions for each type (positive or negative) of AMM-AZM interaction. Observational datasets, and long-simulations from PIcontrol and historical CMIP6 simulations will be used.
How to cite: Martín-Rey, M., Rodríguez-Fonseca, B., Losada, T., and Polo, I.: Precursor mechanisms and multidecadal modulation of the Atlantic Meridional Mode-Atlantic Zonal Mode connection, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10610, https://doi.org/10.5194/egusphere-egu26-10610, 2026.
Sea Surface Temperatures (SST) in the Southeastern Tropical Atlantic Ocean off Angola and Namibia feature pronounced variability on interannual time scales with impacts on the marine ecosystem and rainfall over Southwest Africa. Extreme warm and cold events, so called Benguela Niños and Niñas, are typically remotely forced by wind changes in the western equatorial Atlantic and subsequent Kelvin and coastal trapped wave propagation. Local processes such as coastal wind variations, air-sea heat flux anomalies and freshwater anomalies can additionally drive or amplify the events. Freshwater and thereby salinity anomalies, which have only recently been discussed as a local forcing, are mostly related to anomalous discharge of the Congo river.
In this study, we use an extensive in-situ data set in an attempt to quantify the impact that these sea surface salinity variations have on the mixed-layer turbulent heat fluxes and consequently on Benguela Niños and Niñas. We find that the impact occurs via the changes in stratification with fresh anomalies leading to stronger surface layer stratification, which reduces the mixing with cold waters from below, thus enhancing SSTs. Comparing the 1995 Benguela Niño that featured very low salinity values with the 1997 Benguela Niña that was accompanied by high surface salinity, the mixed layer turbulent heat loss was found to be three times lower in the former case than in the latter. In general, interannual variations in surface salinity, dominated by salt advection, strongly impact the heat exchange between the ocean surface and subsurface layer off Angola in early boreal spring when the Congo river discharge is at its seasonal maximum.
How to cite: Lübbecke, J., Aroucha, L. C., and Hummels, R.: How sea surface salinity variability contributes to ocean turbulent heat fluxes during Benguela Niños and Niñas, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1850, https://doi.org/10.5194/egusphere-egu26-1850, 2026.
Using seasonal predictions from the ECMWF SEAS-5 System, we analyze the relationship between ENSO and upwelling indices in the regions of Benguela.
We find that reanalysis show correlations between El Niño and the Southern Oscillation phenomenon (ENSO) and upwelling indices in February-March-April. The system performs a very accurate prediction in the Tropics of the Sea Surface Temperature (SST) and wind stress variables leading to a good simulation of El Niño, but to a less realistic simulation of Benguela upwelling.
The simulation of the connection between ENSO and Benguela depends on the latitude studied: Northern Benguela Eastern Boundary Upwelling System (EBUS) is more related with ENSO than Southern Benguela EBUS.
There are also changes in the predictability depending on the period of study. We focus in two periods: 1981-1998 (P1) and 1999-2016. In SEAS-5 there is a clear relationship between Northern Benguela Upwelling System and ENSO that appears to be consistent and similar for the two periods, while in observations the relation appears to be robust only after the year 2000’s. This result highlights the importance of taking into account the impact of changes in the background state on predictability.
How to cite: Losada, T., Martín-Gómez, V., Rodríguez-Fonseca, B., Polo, I., and Martín-Rey, M.: SEAS5 skill of ENSO impact on Northern Benguela Coastal Upwelling Systems , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14892, https://doi.org/10.5194/egusphere-egu26-14892, 2026.
Historical Coupled Model Intercomparison Project Phase 6 (CMIP6) model outputs are analyzed to evaluate models' ability in simulating the seasonal and interannual variability in the South-Eastern Atlantic Ocean. The study focuses on SST in February-March-April, the main season of occurrence of the extreme interannual warm and cold Benguela Niño-Niña events.
In the Angola-Benguela-Area (ABA), the CMIP6 SST ensemble-mean resembles the seasonality of the observations but with a strong bias. Unlike the seasonal cycle, the SST interannual variability in CMIP6 ensemble-mean is underestimated and occurs 3-4 months after the peak of maximum variability in the observations (June/July). Among the model ensemble, 2 groups of models emerge: a group featuring a maximum interannual variability in the right location (ABA) but delayed by about 2/3 months compared to the observation (~60% of the models); a group featuring the maximum variability in the right season (FMA) but in a location shifted southward in the South-Benguela (~30% of models). For the first group, results suggest that the time-shift of the peak in the SST variability is induced by the time-shift of the equatorial zonal wind stress. For the second group results show that the latitudinal-shift of the peak in SST variability is controlled by intense coastal wind activity in the south Benguela rather than by model bias and a southward shift in the position of Angola-Benguela-Frontal Zone.
Finally, we examined the models’ ability in simulating extreme interannual Benguela Niño-Niña events. Very few individual models correctly simulate the phenology of the Benguela events, including the modulation of the equatorial zonal and coastal winds that drive development in the preceding months. Interestingly most of the best models have in common a fairly good representation of the South-Atlantic High-pressure system.
How to cite: Bachélery, M. L., Keenlyside, N., and Koseki, S.: Evaluation of Benguela Niño/Niña events in the CMIP6 historical simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18312, https://doi.org/10.5194/egusphere-egu26-18312, 2026.
The seasonal evolution of the M2 internal tide (IT) in the Senegalo–Mauritanian Upwelling Region is investigated using three years (2014–2016) of ocean simulations. The results reveal pronounced seasonal variability in M2 IT dynamics north and south of Dakar, primarily driven by seasonal stratification and remotely generated ITs propagating from the Cape Verde area (CVA). Seasonal stratification strongly modulates local tide-topography interactions, with stratification during the downwelling season (months 9-12) beneficial to IT generation. In the South Dakar area (SDA), local IT generation and dissipation co-vary seasonally, featuring an IT energy source. However, the seasonal dissipation is not directly linked to local generation in the North Dakar area (NDA). This contrasting seasonality suggests a strong influence of remotely generated IT from the CVA, which can seasonally penetrate onshore into the NDA, leading to enhanced dissipation during the upwelling season (months 1-4), and reduced dissipation during the relaxation season (months 5-8). Besides, interannual IT variabilities, mesoscale eddies, and seasonal circulation can further complicate the interpretation of coastal seasonal variability. These results highlight the combined effects of seasonal stratification, circulation, and remote IT propagation, playing a crucial role in modulating coastal IT dissipation and mixing across the Senegalo-Mauritania Upwelling Region.
How to cite: Huang, H., Brandt, P., J. Greatbatch, R., Zeng, Z., and Chen, X.: Seasonality of Internal Tide Dynamics in the Senegalo-Mauritanian Upwelling Regions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9571, https://doi.org/10.5194/egusphere-egu26-9571, 2026.
The Canary Upwelling System is among the most productive marine systems in the world. Alongshore winds drive offshore surface Ekman transport and the upward transport of nutrient rich waters from depth, sustaining major fisheries, offshore carbon export, and air–sea CO₂ exchange. Ongoing changes associated with marine heatwaves and potential shifts in wind strength and change in event duration are expected to modify upper ocean stratification, with direct consequences for the depth of source waters supplying coastal upwelling. Previous studies have explored changes in upwelling intensity and source water depth in the Northwest African region using climate model projections and indirect observational indices, including sea surface temperature, wind trends, and Ekman transport-based indices. These approaches have yielded conflicting results, often depending on the datasets, indices, and time scales used. Moreover, empirical metrics commonly used to characterize upwelling do not explicitly resolve how changes in stratification and circulation jointly control the depth of source waters feeding coastal upwelling.
Here, we examine the response of source water depth to variability in wind forcing and upper ocean stratification in the Canary Upwelling System. The analysis focuses on 27-28°N, where the RAPID mooring array provides high time resolution observations from 2015 to 2022. Upper ocean stratification is characterized using satellite and in situ mooring observations, while wind forcing is quantified from atmospheric reanalysis products. Upwelling variability is assessed using a mooring based vertical upwelling index (MUVI) derived from bottom pressure and density measurements, and an Ekman-based upwelling index, the Coastal Upwelling Transport Index (CUTI). Source water depth variability is quantified using density fields and isopycnal displacements from mooring observations. Spectral analyses are applied to wind, stratification, and source water depth time series to identify dominant time scales and assess the relative influence of atmospheric forcing and stratification. This framework also enables the identification of episodic intrusions of South Atlantic Central Water and their association with specific wind and stratification regimes.
By isolating the physical controls on source water depth across weekly to seasonal time scales, this study provides a physical basis for interpreting variability in nutrient supply and ecosystem response in the Canary Upwelling System and informs future assessments of climate driven changes in coastal upwelling dynamics.
How to cite: Cavucci, V.: How Do Source Water Depths Respond to Wind and Stratification Variability in the Northwest African Canary Upwelling System? , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20006, https://doi.org/10.5194/egusphere-egu26-20006, 2026.
How to cite: Bellacanzone, F. and Bordoni, S.: South Tropical Atlantic and South Atlantic Convergence Zone Actively Shape ENSO Diversity: Physical Pathways, Subsurface Modulation, and Long-Lead Prediction, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19537, https://doi.org/10.5194/egusphere-egu26-19537, 2026.
Medicane Daniel, which formed during 4 - 12 September 2023, has stood out as the deadliest recorded storm in Mediterranean history. In this study, we investigate the role of oceanic features in contributing to the intensification of Medicane Daniel. Our findings reveal the presence of a warm core eddy (WCE), high ocean heat content (OHC), and a marine heatwave (MHW) at the location where Medicane Daniel intensified. These features were situated near the coastal region, facilitating the Medicane’s intensification close to the coast. Consequently, the Medicane did not weaken significantly after landfall, leading to severe damage along the coast of Libya. These conditions favoured the intensification of the Medicane and, owing to high moisture convergence, contributed to significant precipitation over the eddy and MHW regions. Observations further indicate that the total water column, low-level vorticity, and humidity at 850 hPa were elevated at the intensification location, reinforcing the Medicane’s intensification and associated heavy precipitation over the eddy and MHW region. Importantly, observations from the high-resolution SWOT satellite captured the WCE more accurately and in finer detail, enabling attribution of changes in biogeochemical properties, namely chlorophyll, phytoplankton, nutrients, and dissolved oxygen concentrations, to eddy-induced vertical mixing and upwelling. The biogeochemical properties tend to increase over the WCE and MHW locations due to enhanced mixing and upwelling associated with these oceanic features. Our case-study analysis suggests that under cyclone conditions, upwelling driven by Ekman pumping may play a more prominent role within WCEs in driving chlorophyll enhancement.
Key Words: Medicanes, Chlorophyll Concentration, Marine Heat Wave, SWOT observations, warm core eddy, Ekman pumping
How to cite: Jangir, B. and Strobach, E.: Interaction Between a Medicane and the Mediterranean Sea: Sea Surface Temperature Anomalies Along the Path of Medicane Daniel, the Deadliest Mediterranean Cyclone, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20748, https://doi.org/10.5194/egusphere-egu26-20748, 2026.
