Abstract
We analyzed seasonal and spatial variations of evapotranspiration (ET) for five Amazon sub-basins and their response to the 2015/16 El Nino episode using a recently developed water-budget approach. ET varied typically between ~7 and 10 cm/month with exception of the Xingu basin for which it varied between 10 and 15 cm/month. Outstanding features of ET seasonality are (i) generally weak seasonality, (ii) two ET peaks for the two very wet catchments Solimoes and Negro, with one occurring during the wet season and one during the drier season, and (iii) a steady increase of ET during the second half of the dry season for the three drier catchments (Madeira, Tapajos, Xingu). Peak ET occurs during the first half of the wet season consistent with leaf flush occurring before the onset of the wet season. With regards to inter-annual variation, we found firstly that for the Solimoes and Madeira catchments the period with large positive wet season anomalies (2012–2015) is associated with negative ET anomalies, and negative SIF (solar induced fluorescence) anomalies. Furthermore, we found negative ET of several cm/months and SIF (up to 50%) anomalies for most of the Amazon basin during the 2015/16 El Nino event suggesting down-regulation of productivity as a main factor of positive carbon flux anomalies during anomalously hot and dry conditions. These results are of interest in view of predicted warmer and more erratic future climate conditions.
Highlights
The Amazon is one of the most significant watersheds on the Earth (Foley et al, 2002)
The three outstanding features of ET seasonality are (i) the generally weak seasonality, (ii) two ET peaks for the two very wet catchments Solimões and Negro), with one occurring during the wet season and one during the drier season, suggesting a dual control of precipitation and radiation, and (iii) a steady increase of ET during the second half of the dry season for the three drier catchments (Madeira, Tapajos, Xingu), with peak ET occurring during the first half of the wet season consistent with leaf flush occurring before the onset of the wet season (Saleska et al., 2003)
These results are of interest in view of predicted warmer and more erratic future climate conditions
Summary
The Amazon is one of the most significant watersheds on the Earth (Foley et al, 2002). With a vast network of freshwater systems containing watercourses, and extended seasonal floodplains, Amazonia plays a vital role in the global hydrological cycle. It discharges approximately 20% of the Earth’s freshwater to the sea (Foley et al, 2002). The Amazon basin contains the largest area of tropical rainforest (e.g., Hansen et al, 2013) These forests contribute nearly 10% of the Earth’s terrestrial productivity and vegetation biomass (Brienen et al, 2015), and provide habitats to numerous animal and plant species (Foley et al, 2002).
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