Amplified seasonal cycle in hydroclimate over the Amazon river basin and its plume region

Yu-Chiao Liang,Chia-Wei Lan,Hyodae Seo,Ren-Jie Wu,Caroline C Ummenhofer,Min-Hui Lo,Stephen Yeager,John D Steffen

doi:10.1038/s41467-020-18187-0

Yu-Chiao Liang, Chia-Wei Lan + Show 6 more

Open Access

https://doi.org/10.1038/s41467-020-18187-0

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Abstract

The Amazon river basin receives ~2000 mm of precipitation annually and contributes ~17% of global river freshwater input to the oceans; its hydroclimatic variations can exert profound impacts on the marine ecosystem in the Amazon plume region (APR) and have potential far-reaching influences on hydroclimate over the tropical Atlantic. Here, we show that an amplified seasonal cycle of Amazonia precipitation, represented by the annual difference between maximum and minimum values, during the period 1979–2018, leads to enhanced seasonalities in both Amazon river discharge and APR ocean salinity. An atmospheric moisture budget analysis shows that these enhanced seasonal cycles are associated with similar amplifications in the atmospheric vertical and horizontal moisture advections. Hierarchical sensitivity experiments using global climate models quantify the relationships of these enhanced seasonalities. The results suggest that an intensified hydroclimatological cycle may develop in the Amazonia atmosphere-land-ocean coupled system, favouring more extreme terrestrial and marine conditions.

Highlights

The Amazon river basin receives ~2000 mm of precipitation annually and contributes ~17% of global river freshwater input to the oceans; its hydroclimatic variations can exert profound impacts on the marine ecosystem in the Amazon plume region (APR) and have potential farreaching influences on hydroclimate over the tropical Atlantic
Amazon plume region (APR), which is characterized by relatively low ocean salinity[3,4,8] and high nutrients brought by the Amazon river discharge[3,4,9,10]
Small differences appear among different observational precipitation datasets (Fig. 1b), indicating the robustness of the estimated annual cycle for the Amazonia precipitation reported in this study

Summary

Introduction

The Amazon river basin receives ~2000 mm of precipitation annually and contributes ~17% of global river freshwater input to the oceans; its hydroclimatic variations can exert profound impacts on the marine ecosystem in the Amazon plume region (APR) and have potential farreaching influences on hydroclimate over the tropical Atlantic. The variability of Amazon freshwater and resultant ocean salinity changes have been suggested to affect tropical Atlantic air–sea interactions[17,18] and the variability of the Atlantic intertropical convergence zone (ITCZ)[19], regional sea-level height changes[20,21,22], as well as to exert potentially far-reaching impacts on the Atlantic meridional overturning circulation (AMOC)[23]. Understanding the mechanisms for changes in the Amazon river discharge and the associated upper ocean stratification in the APR is important for the Atlantic hurricane forecasts and for improved understanding of basin-scale climate variability

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