Fluctuations in the monthly discharge of Guyana Shield rivers, related to Pacific and Atlantic climate variability

Abstract

The discharge variability of the main rivers that drain the Guyana Shield is analysed over the last 50 years using cross-wavelet, coherence and composite analysis involving oceanic and atmospheric variables. We highlight the overall hydro-climatological homogeneity of this region that allowed us to focus on the longest discharge time series available. Therefore, a wavelet cross-analysis was carried out between monthly and seasonal Maroni River discharge at the Langa Tabiki station and selected climate indices. This confirms a strong relationship between the hydrology of the Guyana Shield and the Pacific sea-surface temperature (SST) fluctuations. There is evidence of intermittent influence, of between inter-annual and near decadal scales, of the Atlantic SST fluctuations, in particular around 1970 and 1990. Finally, we show that the links between oceanic regions and high discharge in the rivers of Guyana are realized through the reinforcement of the Walker and Hadley cells between the Amazon and the adjacent oceans and through decreased trade winds and monsoon flux that favour the persistence of humidity over the Guyana Shield.Keywords hydro-climatology; wavelet analysis; SST-hydrology connections; Guyana Variations des débits mensuels des fleuves drainant le bouclier guyanais en relation avec la variabilité climatique atlantique et pacifique Résumé Nous analysons la variabilité des principaux fleuves qui drainent le bouclier guyanais au cours des cinquante dernières années en utilisant les analyses en ondelettes croisées, la cohérence en ondelettes et l'analyse composite en prenant en compte des forçages océaniques et atmosphériques. Nous avons tout d'abord mis en évidence une homogénéité hydro-climatologique globale dans cette région qui nous a permis de nous concentrer sur les séries hydrologiques disponibles les plus longues. Ainsi, une analyse en ondelettes croisées a été réalisée entre les débits mensuels et saisonniers du fleuve Maroni à la station de Langa Tabiki et différents indices climatiques. Elle a confirmé une relation forte entre l'hydrologie du plateau guyanais et les variations des températures de surface du Pacifique. Nous avons pu mettre en évidence une influence intermittente des températures de surface de l'Océan Atlantique à des échelles interannuelles et décennales, en particulier autour des années 1970 et 1990. Enfin, nous avons montré que les liens entre les influences des différentes régions océaniques et les débits maximaux relevés dans les fleuves guyanais sont influencés d'une part par le renforcement des cellules de Walker

Characterization of the Interannual Variability of Precipitation and Streamflow in Tensift and Ksob Basins (Morocco) and Links with the NAO

“…For example, the El Niño-Southern Oscillation (ENSO) is a sea-surface temperature fluctuation observed over the tropical Pacific Ocean that impacts precipitation in many locations around the globe, from South America to Africa, Australia and North America [5]. Labat et al [6] performed a cross-wavelet analysis on a monthly and seasonal basis through various climatic indices over the Maroni River. They confirmed a strong relationship between the hydrology of the Guyana shelf and Marrakesh.…”

Exposure assessment of rainfall to interannual variability using the wavelet transform

“…Thus, results in Figure and Table are in agreement with the expected spatial pattern for Tocantins state considering that its Northern stations are closer to known regions commonly influenced by regional climate forcings, especially over the Amazon basin. Previous studies identified the interannual and decadal variability as the strongest influences over the region, mainly associated with ENSO and the gradient of SST over the tropical Atlantic (Espinoza et al, ; Espinoza et al, ; Labat et al, ; Espinoza et al, ; Marengo and Espinoza, ). In addition, transitions from drought to floods have been reported over northern South America (Espinoza et al, ; Arias et al, ).…”

“…The advantage of the technique is that intermittent influences are better identified in comparison with the traditional Fourier transform, which is based on sine and cosine functions that extend over the whole record. The wavelet transform has been used in many studies recently, including the characterization of turbulence over plant canopies (Collineau and Brunet, ; Krusche and De Oliveira, ), variability of pollutants concentrations (Zeri et al, ) and climate studies, among others (Torrence and Compo, ; Grinsted et al, ; Labat et al, ; Apaéstegui et al, ).…”

Dynamics and fluxes of organic carbon and nitrogen in two Guiana Shield river basins impacted by deforestation and mining activities

“…The climate in both basins is equatorial and is characterized by wet (December–February and April–July) and dry (August–November) seasons controlled by the intertropical convergence zone and El Niño/La Niña events in relation to the Atlantic and Pacific Ocean surface temperature (Gaucherel, ; Labat et al, ). The air temperature throughout the year commonly varies from 22 °C to 33 °C, with extreme values of 17 °C and 35 °C (Héritier, ).…”