Projected increases in intensity, frequency, and terrestrial carbon costs of compound drought and aridity events

Sha Zhou; Yao Zhang; A Park Williams; Pierre Gentine

doi:10.1126/sciadv.aau5740

Projected increases in intensity, frequency, and terrestrial carbon costs of compound drought and aridity events

Sci Adv. 2019 Jan 23;5(1):eaau5740. doi: 10.1126/sciadv.aau5740. eCollection 2019 Jan.

Authors

Sha Zhou¹, Yao Zhang¹, A Park Williams², Pierre Gentine^{1

3}

Affiliations

¹ Department of Earth and Environmental Engineering, Columbia University, New York, NY 10027, USA.
² Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA.
³ Earth Institute, Columbia University, New York, NY 10027, USA.

Abstract

Drought and atmospheric aridity pose large risks to ecosystem services and agricultural production. However, these factors are seldom assessed together as compound events, although they often occur simultaneously. Drought stress on terrestrial carbon uptake is characterized by soil moisture (SM) deficit and high vapor pressure deficit (VPD). We used in situ observations and 15 Earth system models to show that compound events with very high VPD and low SM occur more frequently than expected if these events were independent. These compound events are projected to become more frequent and more extreme and exert increasingly negative effects on continental productivity. Models project intensified negative effects of high VPD and low SM on vegetation productivity, with the intensification of SM exceeding those of VPD in the Northern Hemisphere. These results highlight the importance of compound extreme events and their threats for the capability of continents to act as a carbon sink.