Sensitivity of Amazon Carbon Balance to Climate and Human-Driven Changes

Amazon is the major tropical land regions and is still been poorly comprehend, with only very few regular greenhouse gas measurements available in the tropics, and mostly not of a suitable nature for estimating carbon balances. Amongst the land regions in the tropics of particular importance for the global carbon cycle is the Amazon, by far the largest region hosting the largest carbon pool in vegetation and soils (~200 PgC). Net carbon exchange between tropical land and the atmosphere is potentially important because it holds large amounts of carbon in forests and soils which can be released on short time-scales e.g. via deforestation or changes in growing conditions, like increased heat and the extension of dry season. Such changes may thus cause feedbacks on global climate.

In the last 40 years Amazon show a temperature increase of 1.1ºC and a extension of dry season. In the annual mean the reduction in precipitation in these 40 years is 50.5mm, but this reduction happens in dry season, producing more stress for the forest with consequences in Carbon Balance.

A study with regional representativeness, from 2010 onwards a greenhouse gas measurement program measurement based on regular vertical profiles of CO₂, CH₄, N₂O, CO, SF6, from the ground up to 4.5 km height at four sites along the main air-stream over the Amazon. Here we will report what these data tell us about greenhouse gas balances and its controls over the period from 2010-2017. In this period we performed 513 vertical profiles over 4 regions representing east to west and north to south of Amazon. The observed variability in Carbon Balance during these 8 years is correlated with climate variability (Temperature, precipitation, GRACE) and human-driven changes (Fire counts). The correlations were performed inside each influenced area for each studied site.

It was observed a consistent source from the Amazon (natural plus anthropogenic sources) to the atmosphere, where during this period Amazon was a consistent source with the mean for Amazon of 0.4 ± 0.2 PgC/year, considering the area like 7.2 millions km². Fire emissions are the main source of carbon to the atmosphere and the Amazon forest promote a removal from minor part of these emissions