Flood Impacts on Net Ecosystem Exchange in the Midwestern and Southern
United States in 2019
Abstract
Climate extremes such as droughts, floods, heatwaves, frosts, and
windstorms add considerable variability to the global year-to-year
increase in atmospheric CO2 through their influence on terrestrial
ecosystems. While the impact of droughts on terrestrial ecosystems has
received considerable attention, the response to flooding events of
varying intensity is poorly understood. To improve upon such
understanding, the impact of the 2019 US flooding on regional CO2
vegetation fluxes is examined in the context of 2017-2018 years when
such precipitation anomalies are not observed. CO2 is simulated with
NASA’s Global Earth Observing System (GEOS) combined with the Low-order
Flux Inversion (LoFI), where fluxes of CO2 are estimated using a suite
of remote sensing measurements including greenness, night lights, and
fire radiative power and bias corrected based on in situ observations.
Net ecosystem exchange CO2 tracer is separated into the three regions
covering the Midwest, South, and Eastern Texas and adjusted to match CO2
observations from towers located in Iowa, Mississippi, and Texas.
Results indicate that for the Midwestern region consisting primarily of
corn and soybeans crops, flooding contributes to a 15-25% reduction of
net carbon uptake in May-September of 2019 in comparison to 2017 and
2018. These results are supported by independent reports of changes in
agricultural activity. For the Southern region, comprised mainly of
non-crop vegetation, net carbon uptake is enhanced in May-September of
2019 by about 10-20% in comparison to 2017 and 2018. These outcomes
show the heterogeneity in effects that excess wetness can bring to
diverse ecosystems.