Monitoring ecosystem-atmosphere co₂ exchange respose to recent (2015-2016) climate variability using the smap l4 carbon product

The recent two years have been characterized by contrasting climatic variability across the globe driven by the onset of a strong El Niño event and relaxation back to ENSO neutral conditions. We investigated the global pattern and seasonal cycle of net ecosystem-atmosphere CO₂ exchange (NEE) for 2015 and 2016 using satellite observation based estimates from the NASA Soil Moisture Active Passive (SMAP) mission. The SMAP Level 4 Carbon product (L4C) was previously validated using globally-distributed eddy covariance flux tower observations and other independent observations. For this study, we investigated L4C seasonal and annual anomalies for vegetation productivity and NEE relative to baseline carbon flux estimates determined from the L4C model-based historical (2001-2012) climatology. Our results reveal large global carbon flux anomalies associated with ENSO related events. Australia transitioned from slightly anomalous CO₂ release under dry conditions in 2015 to a strong CO₂ sink in response to record precipitation in 2016. We also find contrasting seasonally-dependent CO₂ source/sink anomalies between the borealand temperate-northern latitudes which began in 2015 and persisted through 2016, associated with early spring onset, hot and dry summers, and an El Niño-enhanced temperate monsoon. These results highlight the capability of the SMAP L4C product for continued global monitoring of terrestrial ecosystems, including environmental and drought related impacts on vegetation growth, carbon sink strength and associated ecosystem goods and services.