Relationships between pacific and atlantic ocean sea surface temperatures and water levels from satellite altimetry data in the Amazon rivers

Mylena Vieira Silva,Joecila Santos Da Silva,Luiz Antonio Cândido,Stéphane Calmant,Adrien Paris

doi:10.1590/2318-0331.231820170148

Abstract

ABSTRACT The influence of SST (Sea Surface Temperature) of adjacent oceans on the variability of water levels in the Amazon basin was investigated by using radar altimetry from the ENVISAT and Jason-2 missions. Data from the in situ network was used to compare the correlations of water level and SST anomalies in the sub-basins of the Amazonas-Peru, Solimões, Negro and Madeira Rivers. The analysis was made on the monthly and annual scales between 2003 and 2015. The correlations with anomalies of levels from altimetry presented higher accuracy indices than those from the conventional network. In general, ATN and PAC are better correlated with the entire basin. During the flood months, most of the sub-basins presented negative associations with ATN. In the months of ebb, the response to the indexes varies according to the region. The satellite altimetry data permitted to reach regions non-monitored by the conventional network. We also analyzed the impacts of hydrological extremes in all these sub-regions in the last 13 years. In Western Amazon, the drought of 2010 stands out, associated with the warming of the Tropical Atlantic and the El Niño. In the Negro River, the water level anomalies were the lowest in the basin during the 2005 drought. In the Purus River, the effects of the 2010 drought that affected the entire Amazon, were higher in 2011 due to its strong relationship with the Atlântic and Pacific oceans. In general, hydrological extremes are stronger or highlighted when SST increases simultaneously in both oceans.

Highlights

The Amazonian rivers are extensive, with natural flows involving several elements
The least rainy season occurs between the months of June and September; the response time to precipitation varies between 2 to 3 months; h) Tapajós River - the months of flood occur between November and April, reaching higher values in March; the peak of flood coincides with month of higher rainfall totals; as of May, the level of this river begins to fall, reaching minimum values in September during the less rainy season of the eastern Amazon; i) Xingu River - months of flood occur between November and April, with maximum levels in March, coinciding with the maximum precipitation; the least rainy period occurs between the months of June and September, the same period in which the ebb occurs, with minimum quotas in September
The SST climatic indexes of NTA, Southern Tropical Atlantic (STA) and Pacific Ocean (PAC) region 3.4 were used for comparison, which are nothing but the average SST anomalies in these different regions

Summary

Introduction

The Amazonian rivers are extensive, with natural flows involving several elements. The flow rate is influenced by the low water table slope of the order of 10 to 40 mm/Km (CALMANT et al, 2013) in the alluvial plain of the Solimões-Amazonas River, due to the large water table amplitude (SILVA et al, 2010), and by the regional characteristics of its affluent linked to the basin rainfall regime (RONCHAIL et al, 2005; ESPINOZA VILLAR et al, 2009). It does not correspond to a classical flow from upstream to downstream, but to a displacement of the waters pushed by the flood wave of Andean rivers (MOLINIER et al, 1996), forming a vast water system of which society is strongly dependent Parallel to this scenario of hydrological complexity, in the last decades, extreme hydrological events affected the Amazon basin, causing considerable social damages to the riverside populations, causing transportation and navigation difficulties, food shortages, and ecological damages, potentially aggravated by the effects abnormal climatic conditions. These anomalies are strongly influenced by the temperature variability of the Pacific and Tropical Atlantic (TA) oceans (MARENGO; ESPINOZA, 2016). Best predictions were found for stations in the southern portion of the Amazon River when the Atlantic Ocean sea surface temperature was used, instead

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