Person: Polo Sánchez, Irene
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First Name
Irene
Last Name
Polo Sánchez
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Física de la Tierra y Astrofísica
Area
Física de la Tierra
Identifiers
6 results
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Now showing 1 - 6 of 6
Item Can the boundary profiles at 26ºN be used to extract buoyancy-forced Atlantic Meridional Overturning Circulation signals?(Ocean science, 2020) Polo Sánchez, Irene; Haines, Keith; Robson, Jon; Thomas, ChristopherThe temporal variability of the Atlantic Meridional Overturning Circulation (AMOC) is driven both by direct wind stresses and by the buoyancy-driven formation of North Atlantic Deep Water over the Labrador Sea and Nordic Seas. In many models, low-frequency density variability down the western boundary of the Atlantic basin is linked to changes in the buoyancy forcing over the Atlantic subpolar gyre (SPG) region, and this is found to explain part of the geostrophic AMOC variability at 26◦ N. In this study, using different experiments with an ocean general circulation model (OGCM), we develop statistical methods to identify characteristic vertical density profiles at 26◦ N at the western and eastern boundaries, which relate to the buoyancy-forced AMOC. We show that density anomalies due to anomalous buoyancy forcing over the SPG propagate equatorward along the western Atlantic boundary (through 26◦ N), eastward along the Equator, and then poleward up the eastern Atlantic boundary. The timing of the density anomalies appearing at the western and eastern boundaries at 26◦ N reveals ∼ 2– 3-year lags between boundaries along deeper levels (2600– 3000 m). Record lengths of more than 26 years are required at the western boundary (WB) to allow the buoyancy-forced signals to appear as the dominant empirical orthogonal function (EOF) mode. Results suggest that the depth structure of the signals and the lagged covariances between the boundaries at 26◦ N may both provide useful information for detecting propagating signals of high-latitude origin in more complex models and potentially in the observational RAPID (Rapid Climate Change programme) array. However, time filtering may be needed, together with the continuation of the RAPID programme, in order to extend the time period.Item Impact of equatorial Atlantic variability on ENSO predictive skill(Nature communications, 2021) Exarchou, Eleftheria; Ortega, Pablo; Rodríguez De Fonseca, María Belén; Losada Doval, Teresa; Polo Sánchez, Irene; Prodhomme, CloéEl Niño-Southern Oscillation (ENSO) is a key mode of climate variability with worldwide climate impacts. Recent studies have highlighted the impact of other tropical oceans on its variability. In particular, observations have demonstrated that summer Atlantic Niños (Niñas) favor the development of Pacific Niñas (Niños) the following winter, but it is unclear how well climate models capture this teleconnection and its role in defining the seasonal predictive skill of ENSO. Here we use an ensemble of seasonal forecast systems to demonstrate that a better representation of equatorial Atlantic variability in summer and its lagged teleconnection mechanism with the Pacific relates to enhanced predictive capacity of autumn/winter ENSO. An additional sensitivity study further shows that correcting SST variability in equatorial Atlantic improves different aspects of forecast skill in the Tropical Pacific, boosting ENSO skill. This study thus emphasizes that new efforts to improve the representation of equatorial Atlantic variability, a region with long standing systematic model biases, can foster predictive skill in the region, the Tropical Pacific and beyond, through the global impacts of ENSO.Item ENSO coupling to the equatorial Atlantic: analysis with an extended improved recharge oscillator model(Frontiers in Marine Science, 2023) Crespo Miguel, Rodrigo; Polo Sánchez, Irene; Mechoso, Carlos R.; Rodríguez De Fonseca, María Belén; Cao García, Francisco JavierIntroduction: Observational and modeling studies have examined the interactions between El Niño-Southern Oscillation (ENSO) and the equatorial Atlantic variability as incorporated into the classical charge-recharge oscillator model of ENSO. These studies included the role of the Atlantic in the predictability of ENSO but assumed stationarity in the relationships, i.e., that models’ coefficients do not change overtime. Arecentworkbytheauthors has challenged the stationarity assumption in the ENSO framework but without considering the equatorial Atlantic influence on ENSO. Methods: The present paper addresses the changing relationship between ENSO and the Atlantic El Niño using an extended version of the recharge oscillator model. The classical two-variable model of ENSO is extended by adding a linear coupling on the SST anomalies in the equatorial Atlantic. The model’s coefficients are computed for different periods. This calculation is done using two methods tofitthemodel tothe data: (1) the traditional method (ReOsc), and (2) a novel method (ReOsc+) based on fitting the Fisher’s Z transform of the auto and cross-correlation functions. Results: Weshowthat, duringthe 20th century, the characteristic dampingrate of the SST and thermocline depth anomalies in the Pacific have decreased in time by a factor of 2 and 3, respectively. Moreover, the damping time of the ENSO fluctuations has doubled from 10 to 20 months, and the oscillation period of ENSO has decreased from 60-70 months before the 1960s to 50 months afterward. These two changes have contributed to enhancing ENSO amplitude. The results also show that correlations between ENSO and the Atlantic SST strengthened after the 70s and the way in which the impact of the equatorial Atlantic is added to the internal ENSO variability. Conclusions: The remote effects of the equatorial Atlantic on ENSO must be considered in studies of ENSO dynamics and predictability during specific time-periods. Our results provide further insight into the evolution of the ENSO dynamics anditscoupling to the equatorial Atlantic, as well as an improved tool to study the coupling of climatic and ecological variables.Item Ocean dynamics shapes the structure and timing of Atlantic Equatorial Modes(Journal of geophysical research-oceans, 2019) Martín Rey, Marta; Polo Sánchez, Irene; Rodríguez De Fonseca, María Belén; Lazar, Alban; Losada Doval, TeresaA recent study has brought to light the co‐existence of two distinct Atlantic Equatorial Modes during negative phases of the Atlantic Multidecadal Variability: the Atlantic Niño and Horse‐Shoe (HS) mode. Nevertheless, the associated air‐sea interactions for HS mode have not been explored so far and the prevailing dynamic view of the Atlantic Niño has been questioned. Here, using a forced ocean model simulation, we find that for both modes, ocean dynamics is essential to explain the equatorial SST variations, while air‐sea fluxes control the off‐equatorial SST anomalies. Moreover, we demonstrate the key role played by ocean waves in shaping their distinct structure and timing. For the positive phase of both Atlantic Niño and HS, anomalous westerly winds trigger a set of equatorial downwelling Kelvin waves (KW) during spring‐summer. These dKWs deepen the thermocline, favouring the equatorial warming through vertical diffusion and horizontal advection. Remarkably, for the HS, an anomalous north‐equatorial wind stress curl excites an upwelling Rossby wave (RW), which propagates westward and is reflected at the western boundary becoming an equatorial upwelling KW. The uKW propagates to the east, activating the thermocline feedbacks responsible to cool the sea surface during summer months. This RW‐reflected mechanism acts as a negative feedback causing the early termination of the HS mode. Our results provide an improvement in the understanding of the TAV modes and emphasize the importance of ocean wave activity to modulate the equatorial SST variability. These findings could be very useful to improve the prediction of the Equatorial Modes.Item Skillful prediction of tropical Pacific fisheries provided by Atlantic Niños(Environmental research letters, 2021) Gómara Cardalliaguet, Íñigo; Rodríguez De Fonseca, María Belén; Mohino Harris, Elsa; Losada Doval, Teresa; Polo Sánchez, Irene; Coll, MartaTropical Pacific upwelling-dependent ecosystems are the most productive and variable worldwide, mainly due to the influence of El Niño Southern Oscillation (ENSO). ENSO can be forecasted seasons ahead thanks to assorted climate precursors (local-Pacific processes, pantropical interactions). However, due to observational data scarcity, little is known about the importance of these precursors for marine ecosystem prediction. Previous studies based on Earth System Model simulations forced by observed climate have shown that multiyear predictability of tropical Pacific marine primary productivity is possible. With recently released global marine ecosystem simulations forced by historical climate, full examination of tropical Pacific ecosystem predictability is now feasible. By complementing historical fishing records with marine ecosystem model data, we show herein that equatorial Atlantic sea surface temperatures (SSTs) constitute a valuable predictability source for tropical Pacific fisheries, which can be forecasted over large-scale areas up to three years in advance. A detailed physical-biological mechanism is proposed whereby equatorial Atlantic SSTs influence upwelling of nutrient-rich waters in the tropical Pacific, leading to a bottom-up propagation of the climate-related signal across the marine food web. Our results represent historical and near-future climate conditions and provide a useful springboard for implementing a marine ecosystem prediction system in the tropical Pacific.Item The tropical Atlantic observing system(Frontiers in Marine Science, 2019) Rodríguez De Fonseca, María Belén; Polo Sánchez, Irene; Losada Doval, Teresa; Mohino Harris, Elsa; López Parages, JorgeThe tropical Atlantic is home to multiple coupled climate variations covering a wide range of timescales and impacting societally relevant phenomena such as continental rainfall, Atlantic hurricane activity, oceanic biological productivity, and atmospheric circulation in the equatorial Pacific. The tropical Atlantic also connects the southern and northern branches of the Atlantic meridional overturning circulation and receives freshwater input from some of the world’s largest rivers. To address these diverse, unique, and interconnected research challenges, a rich network of ocean observations has developed, building on the backbone of the Prediction and Research Moored Array in the Tropical Atlantic (PIRATA). This network has evolved naturally over time and out of necessity in order to address the most important outstanding scientific questions and to improve predictions of tropical Atlantic severe weather and global climate variability and change. The tropical Atlantic observing system is motivated by goals to understand and better predict phenomena such as tropical Atlantic interannual to decadal variability and climate change; multidecadal variability and its links to the meridional overturning circulation; air-sea fluxes of CO2 and their implications for the fate of anthropogenic CO2; the Amazon River plume and its interactions with biogeochemistry, vertical mixing, and hurricanes; the highly productive eastern boundary and equatorial upwelling systems; and oceanic oxygen minimum zones, their impacts on biogeochemical cycles and marine ecosystems, and their feedbacks to climate. Past success of the tropical Atlantic observing system is the result of an international commitment to sustained observations and scientific cooperation, a willingness to evolve with changing research and monitoring needs, and a desire to share data openly with the scientific community and operational centers. The observing system must continue to evolve in order to meet an expanding set of research priorities and operational challenges. This paper discusses the tropical Atlantic observing system, including emerging scientific questions that demand sustained ocean observations, the potential for further integration of the observing system, and the requirements for sustaining and enhancing the tropical Atlantic observing system.