Preprints
https://doi.org/10.5194/cp-2021-75
https://doi.org/10.5194/cp-2021-75

  29 Jun 2021

29 Jun 2021

Review status: this preprint is currently under review for the journal CP.

Effect of nitrogen limitation and soil processes on mid–Holocene greening of the Sahara

Jooyeop Lee1, Martin Claussen2,3, Jeongwon Kim1, Je-Woo Hong4, In-Sun Song5, and Jinkyu Hong1 Jooyeop Lee et al.
  • 1Ecosystem-Atmosphere Process Laboratory, Department of Atmospheric Sciences, Yonsei University, Seoul, Korea (Republic of)
  • 2Max-Planck-Institut für Meteorologie, Hamburg, Germany
  • 3Center for Earth System Research and Sustainability (CEN), Universität Hamburg, Germany
  • 4Korea Adaptation Center for Climate Change, Korea Environment Institute, Sejong, Korea (Republic of)
  • 5Mathematical Atmospheric Physics Lab, Department of Atmospheric Sciences, Yonsei University, Seoul, Korea (Republic of)

Abstract. The so–called Green Sahara (GS), wet and vegetative Sahara region in the mid–Holocene, provides useful information on our climate simulation because it is consequence of complex interaction between biophysical and climatic processes. It is still a challenge to simulate the GS in terms of vegetative extent and precipitation using the current climate models. This study attempts to simulate the Green Sahara by using the state–of–the–art earth system model CESM that incorporates the nitrogen cycle and the soil–albedo–precipitation feedback. Our study focuses on the impact of soil biophysical properties and soil nitrogen on the simulation of the GS. With changes in the Earth’s orbit and dust in the mid–Holocene, the model simulates increased precipitation in North Africa, but does not capture the extent of the GS. Further analysis shows that the mid–Holocene greening is simulated better if the amount of soil nitrogen and soil texture are properly modified during the GS period through their influence on photosynthesis and surface albedo and their consequent enhanced albedo– and evapotranspiration–precipitation feedbacks. Our findings suggest that future climate simulation needs to consider consequent changes in soil nitrogen and texture with changes in vegetation cover and density for proper climate simulations.

Jooyeop Lee et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2021-75', Anonymous Referee #1, 29 Aug 2021
  • RC2: 'Comment on cp-2021-75', Anonymous Referee #2, 31 Aug 2021

Jooyeop Lee et al.

Jooyeop Lee et al.

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Short summary
It is still a challenge to simulate the so–called Green Sahara (GS), wet and vegetative Sahara region in the mid–Holocene using current climate models. Our analysis shows that the GS is simulated better if soil nitrogen and soil texture are properly described through their influence on photosynthesis, surface albedo, and evapotranspiration. Future climate simulation needs to consider consequent changes in soil nitrogen and texture with changes in vegetation cover for proper climate simulations.