Amazon River Levels: How Pacific and Atlantic Temperatures Impact Water Levels

The Amazon River's water levels are influenced by a complex interplay of factors, with key drivers being the variability in sea surface temperatures (SSTs) of the Pacific and Atlantic oceans. Specifically, the El Niño-Southern Oscillation (ENSO) in the Pacific and temperature gradients in the Tropical Atlantic can significantly modulate climate patterns across the Amazon, impacting rainfall distribution and, consequently, river levels. Understanding these variations is crucial for managing water resources, navigation, and ensuring the well-being of communities that depend on the river system. The recent occurrence of extreme hydrological events underscores the urgent need to comprehend the driving forces behind these changes. This understanding can improve predictive capabilities and resource management.

Researchers are increasingly using satellite altimetry data to monitor water levels in the Amazon River basin, complementing traditional hydrometric station networks. Satellite data, such as that from the ENVISAT and Jason-2 missions, offers a means of observing water levels in remote and inaccessible regions, providing a more comprehensive understanding of the Amazon's hydrological dynamics. This approach has advantages over traditional methods, as the vastness of the basin and limited density of hydrometric networks pose significant challenges. Satellite altimetry can monitor regions beyond the reach of traditional methods and provide more accurate data for long-term studies.

A study analyzing data from 2003 to 2015 revealed significant correlations between sea surface temperature (SST) fluctuations and river levels in several Amazon sub-basins. For example, the Amazonas-Peru sub-basin shows a strong link with the Pacific Ocean during peak ebb months and negative correlations with the Tropical North Atlantic throughout much of the year. The Solimões River exhibits a clear positive correlation with the Pacific and a negative correlation with the Tropical Atlantic, strongest during flood months. The Negro River displays a negative correlation with the Pacific, particularly in its upper reaches, while the lower Negro shows a negative correlation with the Tropical North Atlantic during peak flood months. The Madeira River demonstrates strong correlations with both the Tropical North Atlantic and Pacific, with negative correlations observed for the Tropical North Atlantic during flood months.

Hydrological extremes in the Amazon River basin are often amplified when sea surface temperatures (SSTs) increase simultaneously in both the Pacific and Atlantic oceans. For example, the 2010 drought in the Western Amazon was linked to warming in the Tropical Atlantic and El Niño. The Negro River experienced its lowest water levels during the 2005 drought. The Purus River felt the effects of the 2010 drought more intensely in 2011 due to its strong connection with both the Atlantic and Pacific oceans. The interplay between SST anomalies in the Pacific, influenced by phenomena like El Niño, and the Atlantic can exacerbate these extreme hydrological events.

The Surface Water and Ocean Topography (SWOT) satellite is designed to collect 2D images of the sea surface at 1km² resolution. It is expected to revolutionize the study of hydrological responses in the context of hydroclimatic studies. By providing improved spatial and temporal coverage, as well as enhanced measurements in continental and coastal areas, SWOT paves the way for improved monitoring of water levels in the Amazon River basin and similar environments worldwide. SWOT's ability to capture detailed surface water dynamics will enhance our understanding of the complex relationships between ocean temperatures and river hydrology, leading to more effective water resource management and climate adaptation strategies. While the study mentioned limitations of the data's temporal resolution, SWOT addresses these limitations.