Variabilidad Intra-estacional de la Onda de Kelvin Ecuatorial en el Pacífico (2000-2007): Simulación Numérica y datos observados

El presente trabajo describe e interpreta, en términos de ondas ecuatoriales, la variabilidad de la anomalía del nivel del mar (ANM) y la anomalía de la velocidad zonal (AVZ) en el Pacífico Ecuatorial en el periodo 2000-2007. Para esto, se implementó un modelo numérico oceánico simple de un modo baroclínico de esfuerzo de viento. En una primera etapa, el modelo fue validado sobre el periodo 1993-2000 usando datos de forzamiento eólico de los satélites ERS-1 y ERS-2. En particular, se muestra que el uso de una fricción cuadrática permite reproducir mejor la variabilidad de la ANM y las AVZ. En una segunda etapa, se realizó una simulación de estudio para el periodo 2000-2007. En esta ocasión, se usó el mismo esquema de la simulación anterior y se forzó con anomalías de esfuerzo de viento (AEV) obtenidas del satélite QSCAT para el periodo 2000-2007. Los resultados de la simulación, en la variable ANM, determinan la existencia de perturbaciones con periodos de 45 y 91 días, es decir, perturbaciones intra-estacionales asociadas, en parte, a la variabilidad atmosférica del tipo Madden Julian (Madden and Julian, 1971). Estas oscilaciones también se aprecian en la ANM de TOPEX y la anomalía de la profundidad de la isoterma de 20ºC en 140ºW, pero con poca intensidad. Asimismo, se interpreta que las perturbaciones lineales provocadas por los vientos de periodos de 45 y 91 días, entre 2000-2007, tuvieron repercusión en la variación de la temperatura superficial del mar (TSM) en la zona ecuatorial. El estudio demuestra que aunque la variabilidad interanual durante 2000-2007 fue más débil, en comparación al periodo 1993-1997, se puede simular con un modelo lineal de una sola capa las ondas ecuatoriales a escala temporal intraestacional.Tesi

The intraseasonal equatorial oceanic Kelvin wave and the central Pacific El Niño phenomenon

Descargue el documento en el repositorio institucional de la Université Toulouse III - Paul Sabatier: http://thesesups.ups-tlse.fr/3036Estudia el rol de las ondas oceánicas ecuatoriales en la dinámica y termodinámica a lo largo del Pacífico Central, con el énfasis en El Niño del Pacífico Central del siglo XXI, quiere decir en el rango del 2002-2003.Francia. Beca del Institut de recherche pour le développement (IRD)Tesi

Pronósticos experimentales del posible FEN para la Comisión ENFEN con un modelo de Sistema Tierra de alta resolución para el territorio nacional y el Pacífico oriental

Se reporta la implementación en modo pronóstico del modelo de Sistema Tierra regional ‘IGP Regional Earth System Model CROCO-OASIS-WRF v.1’ (IGP RESM-COW v1) y los pronósticos experimentales del posible FEN 2024, conforme al Plan multisectorial ante la ocurrencia del Fenómeno El Niño 2023 - 2024 (D.S. N° 101-2023-PCM). El modelo IGP RESM-COW v1 tiene una resolución de 12 km para el océano y 30 km para la atmósfera y contempla todo el territorio peruano y parte del Pacífico oriental. La implementación actual toma como insumo los pronósticos del modelo climático global NOAA CFSv2, cuyos sesgos promedio son corregidos usando datos observacionales (MERCATOR y FNL), los promedios climatológicos del CFSv2 y una simulación de 22 años del modelo IGP RESM-COW v1. Esto permite realizar pronósticos de las condiciones oceánicas y atmosféricas con hasta 7 meses de anticipación. El pronóstico experimental con el modelo IGP RESM-COW v1 inicializado con datos de diciembre de 2023 indica que El Niño costero 2023-24 se extendería solo hasta enero de 2024 y las precipitaciones pronosticadas no serían como las que se desarrollaron a fines de verano e inicios-mediados de otoño de 2023 frente a la costa norte

High-Sustained Concentrations of Organisms at Very low Oxygen Concentration Indicated by Acoustic Profiles in the Oxygen Deficit Region Off Peru

International audienceThe oxygen deficient mesopelagic layer (ODL) off Peru has concentrations below 5 μmol O 2 kg –1 and is delimited by a shallow upper oxycline with strong vertical gradient and a more gradual lower oxycline ( lOx ). Some regions show a narrow band of slightly increased oxygen concentrations within the ODL, an intermediate oxygen layer ( iO 2 ). CTD, oxygen and lowered Acoustic Doppler Current Profiler (LADCP, 300 kHz) profiles were taken on the shelf edge and outside down to mostly 2000 m. We evaluate here the acoustic volume backscatter strength of the LADCP signal representing organisms of about 5 mm size. Dominant features of the backscatter profiles were a minimum backscatter strength within the ODL, and just below the lOx a marked backscatter increase reaching a maximum at less than 3.0 μmol O 2 kg –1 . Below this maximum, the acoustic backscatter strength gradually decreased down to 1000 m below the lOx . The backscatter strength also increased at the iO 2 in parallel to the oxygen concentration perturbations marking the iO 2 . These stable backscatter features were independent of the time of day and the organisms represented by the backscatter had to be adapted to live in this microaerobic environment. During daylight, these stable structures were overlapped by migrating backscatter peaks. Outstanding features of the stable backscatter were that at very low oxygen concentrations, the volume backscatter was linearly related to the oxygen concentration, reaching half peak maximum at less than 2.0 μmol O 2 kg –1 below the lOx , and the depth-integrated backscatter of the peak below the lOx was higher than the integral above the Ox. Both features suggest that sufficient organic material produced at the surface reaches to below the ODL to sustain the major fraction of the volume backscatter-producing organisms in the water column. These organisms are adapted to the microaerobic environment so they can position themselves close to the lower oxycline to take advantage of the organic particles sinking out of the ODL

High-Sustained Concentrations of Organisms at Very low Oxygen Concentration Indicated by Acoustic Profiles in the Oxygen Deficit Region Off Peru

The oxygen deficient mesopelagic layer (ODL) off Peru has concentrations below 5 μmol O2 kg–1 and is delimited by a shallow upper oxycline with strong vertical gradient and a more gradual lower oxycline (lOx). Some regions show a narrow band of slightly increased oxygen concentrations within the ODL, an intermediate oxygen layer (iO2). CTD, oxygen and lowered Acoustic Doppler Current Profiler (LADCP, 300 kHz) profiles were taken on the shelf edge and outside down to mostly 2000 m. We evaluate here the acoustic volume backscatter strength of the LADCP signal representing organisms of about 5 mm size. Dominant features of the backscatter profiles were a minimum backscatter strength within the ODL, and just below the lOx a marked backscatter increase reaching a maximum at less than 3.0 μmol O2 kg–1. Below this maximum, the acoustic backscatter strength gradually decreased down to 1000 m below the lOx. The backscatter strength also increased at the iO2 in parallel to the oxygen concentration perturbations marking the iO2. These stable backscatter features were independent of the time of day and the organisms represented by the backscatter had to be adapted to live in this microaerobic environment. During daylight, these stable structures were overlapped by migrating backscatter peaks. Outstanding features of the stable backscatter were that at very low oxygen concentrations, the volume backscatter was linearly related to the oxygen concentration, reaching half peak maximum at less than 2.0 μmol O2 kg–1 below the lOx, and the depth-integrated backscatter of the peak below the lOx was higher than the integral above the Ox. Both features suggest that sufficient organic material produced at the surface reaches to below the ODL to sustain the major fraction of the volume backscatter-producing organisms in the water column. These organisms are adapted to the microaerobic environment so they can position themselves close to the lower oxycline to take advantage of the organic particles sinking out of the ODL

Understanding the impact of climate change on the oceanic circulation in the Chilean island ecoregions

International audienceAbstract Transient mesoscale oceanic eddies in Eastern Boundary Upwelling Systems are thought to strongly affect key regional scale processes such as ocean heat transport, coastal upwelling and productivity. Understanding how these can be modulated at low-frequency is thus critical to infer their role in the climate system. Here we use 26 years of satellite altimeter data and regional oceanic modeling to investigate the modulation of eddy kinetic energy (EKE) off Peru and Chile by ENSO, the main mode of natural variability in the tropical Pacific. We show that EKE tends to increase during strong Eastern Pacific (EP) El Niño events along the Peruvian coast up to northern Chile and decreases off central Chile, while it is hardly changed during Central Pacific El Niño and La Niña events. However the magnitude of the EKE changes during strong EP El Niño events is not proportional to their strength, with in particular the 1972/1973 El Niño event standing out as an extreme event in terms of EKE increase off Peru reaching an amplitude three times as large as that during the 1997/1998 El Niño event, and the 2015/2016 El Niño having instead a weak impact on EKE. This produces decadal changes in EKE, with a similar pattern than that of strong EP El Niño events, resulting in a significant negative (positive) long-term trend off Peru (central Chile)