Satellite Deuterium Observations Quantify Spatio-Temporal Variability of Amazon Water Balance

Abstract:

Changes in the terrestrial Amazon water budget depend on variations in the balance between evapotranspiration and rainfall (E-P). However, large uncertainties in current estimates of E-P make it challenging to quantify its inter-annual to decadal variations and corresponding relationship to variations in temperature or soil moisture. Here we show new satellite observations of deuterium from the NASA AIRS instrument, spanning 2003 to 2019, that can quantify the spatio-temporal variability of E-P over the Amazon. Using evapotranspiration and precipitation measurements, gravity and river discharge data, and a global climate model, we find the uncertainties in the seasonal and spatial variable are comparable to current estimates of E-P over the Amazon but are ~25 to 50% better for the inter-annual and decadal variability. We find that the IAV of the Amazon moisture balance is primarily correlated with ENSO. In addition, comparisons between these new E-P estimates with gravity based terrestrial water storage and precipitation indicate stronger terrestrial influence of ground water on controlling moisture balance in the W. Amazon but more influence from ocean sources and precipitation in the E. Amazon.