Extreme droughts and floods in the Amazon forest

Abstract

In recent years, the Amazon forest has experienced several major droughts (2010, 2015/16) and floods (2012, 2014, 2021). Extreme events represent a threat to the Amazons important functions, but these perturbations also provide valuable insights into the underlying mechanisms. Here we studied the most recent massive drought and flood events in detail, and quantified their severity and spatiotemporal extent relative to a multi-year baseline. First, we describe the anomalous hydrological status of these events, by bringing together a large variety of data sets, including in-situ observations and reanalysis products for precipitation, discharge, vapor pressure deficit and soil moisture. During the strong El Niño conditions following the dry season of 2015, the precipitation fell below its climatological values. This was soon reflected in low discharge rates and soil moisture levels, persisting far into the year 2016 for some regions. In contrast, we find anomalously high precipitation over the northern Amazon during the first months of 2021, resulting in high discharge rates, and rising river levels that have led to massive floods in downstream regions. Finally, we quantified the impact of the 2015/16 drought on vegetation using the inverse model CarbonTacker South America (CT-SAM) and remote sensing proxies for photosynthesis. To address the uncertainty in prior emission estimates, we have used a range of different biosphere models (SiBCASA, SiB4), including a biosphere model linked to a detailed hydrological model (PCR-GLOBWB). For the fire flux we used multiple data sets (GFAS, SiBCASA-GFED4), including a modified version based on CO inversions performed with the TM5-4DVAR system. We find that photosynthesis was reduced during the 2015 drought, especially in the drier, southern part of the Amazon. This was followed by a recovery in the first months of 2016, but during the subsequent dry season a secondary impact on photosynthesis was found. The inversely derived net CO2 fluxes do not have the same high resolution as the satellite products, but when assessed over larger scales, a consistent drought signal is derived.

Authors 12

1. Gerbrand Koren corresponding

   Utrecht University

   Affiliation as printed

   Copernicus Institute of Sustainable Development, Utrecht University, Utrecht, The Netherlands (g.b.koren@uu.nl)

   Copernicus Institute of Sustainable Development, Utrecht University, Utrecht, The Netherlands

2. Santiago Botía corresponding

   Max Planck Institute for Biogeochemistry

   Affiliation as printed

   Max Planck Institute for Biogeochemistry, Department Biogeochemical Signals, Jena, Germany

3. Lucas G. Domingues corresponding

   GNS Science

   Affiliation as printed

   National Isotope Centre, GNS Science, New Zealand

4. Liesbeth Florentie

   Vrije Universiteit Amsterdam

   Affiliation as printed

   VU University, Faculty of Science, Earth and Climate, Amsterdam, The Netherlands

5. Luciana V. Gatti corresponding

   Instituto Nacional de Pesquisas Espaciais

   Affiliation as printed

   National Institute for Space Research (INPE), São José dos Campos, Brazil

6. Manuel U. Gloor

   University of Leeds

   Affiliation as printed

   University of Leeds, School of Geography, Leeds, UK

7. Shaun Harrigan corresponding

   European Centre for Medium-Range Weather Forecasts

   Affiliation as printed

   European Centre for Medium-Range Weather Forecasts (ECMWF), Reading, UK

8. Maarten Krol

   Utrecht University · Wageningen University & Research

   Affiliation as printed

   Institute for Marine and Atmospheric Research Utrecht (IMAU), Utrecht University, Utrecht, The Netherlands

   Wageningen University, Meteorology and Air Quality Group, Wageningen, The Netherlands

9. Ingrid T. Luijkx corresponding

   Wageningen University & Research

   Affiliation as printed

   Wageningen University, Meteorology and Air Quality Group, Wageningen, The Netherlands

10. John Bharat Miller corresponding

    National Oceanic and Atmospheric Administration · NOAA Global Monitoring Laboratory

    Affiliation as printed

    NOAA Global Monitoring Laboratory, Boulder, CO, USA

11. Stijn Naus corresponding Aachen SRON Netherlands Institute for Space Research

    Space Research Organisation Netherlands

    Affiliation as printed

    SRON Netherlands Institute for Space Research, Leiden, The Netherlands

12. Wouter Peters corresponding

    University of Groningen · Wageningen University & Research

    Affiliation as printed

    University of Groningen, Centre for Isotope Research (CIO), Groningen, The Netherlands

    Wageningen University, Meteorology and Air Quality Group, Wageningen, The Netherlands