Vegetation Impact on Atmospheric Moisture Transport under Increasing Land-Ocean Temperature Contrasts

TL;DR

This paper presents a theoretical framework showing how vegetation influences atmospheric moisture transport and how increasing land-ocean temperature contrasts can lead to abrupt changes in moisture regimes, with implications for climate change mitigation.

Contribution

It introduces a novel theoretical analysis of vegetation's role in atmospheric moisture dynamics and identifies critical thresholds in land-ocean temperature contrasts affecting moisture transport.

Findings

Local wind power is sensitive to condensation rates.

Moisture transport can reach a tipping point and reverse with increasing temperature contrast.

Climatological data suggest Eurasia is near a critical threshold.

Abstract

Destabilization of the water cycle threatens human lives and livelihoods. Meanwhile our understanding of whether and how changes in vegetation cover could trigger abrupt transitions in moisture regimes remains incomplete. This challenge calls for better evidence as well as for the theoretical concepts to describe it. Here we briefly summarise the theoretical questions surrounding the role of vegetation cover in the dynamics of a moist atmosphere. We discuss the previously unrecognized sensitivity of local wind power to condensation rate as revealed by our analysis of the continuity equation for a gas mixture. Using the framework of condensation-induced atmospheric dynamics, we then show that with the temperature contrast between land and ocean increasing up to a critical threshold, ocean-to-land moisture transport reaches a tipping point where it can stop or even reverse. Land-ocean temperature contrasts are affected by both global and regional processes, in particular, by the surface fluxes of sensible and latent heat that are strongly influenced by vegetation. Our results clarify how a disturbance of natural vegetation cover, e.g., by deforestation, can disrupt large-scale atmospheric circulation and moisture transport. In view of the increasing pressure on natural ecosystems, successful strategies of mitigating climate change require taking into account the impact of vegetation on moist atmospheric dynamics. Our analysis provides a theoretical framework to assess this impact. The available data for Eurasia indicate that the observed climatological land-ocean temperature contrasts are close to the threshold. This can explain the increasing fluctuations in the continental water cycle including droughts and floods and signifies a yet greater potential importance for large-scale forest conservation.