Enhanced albedo feedback in North Africa from possible combined vegetation and soil-formation processes

It has long been recognized that albedo related vegetation feedbacks amplify climate variability in North Africa. Recent studies have revealed that areas of very high albedo associated with certain desert soil types contribute to the current dry climate of the region. We construct three scenarios of...

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Bibliographic Details
Published in:Climate dynamics 2006-01, Vol.26 (1), p.55-63
Main Authors: Knorr, Wolfgang, Schnitzler, Karl-Georg
Format: Article
Language:English
Subjects:
Albedo
Animal and plant ecology
Animal, plant and microbial ecology
Biological and medical sciences
Climate change
Climate models
Climate variability
Climatology. Bioclimatology. Climate change
Desert soils
Deserts
Earth orbits
Earth, ocean, space
Exact sciences and technology
External geophysics
Fundamental and applied biological sciences. Psychology
Holocene
Meteorology
Sea surface temperature
Soil formation
Soil types
Synecology
Terrestrial ecosystems
Transition zone
Vegetation
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Summary:It has long been recognized that albedo related vegetation feedbacks amplify climate variability in North Africa. Recent studies have revealed that areas of very high albedo associated with certain desert soil types contribute to the current dry climate of the region. We construct three scenarios of North African albedo, one based on satellite measurements, one where the highest albedo resembles that of soils in the desert transition zones, and one based on a vegetation map for the “green Sahara” state of the middle Holocene, ca. 6,000 years ago. Using a series of climate model simulations, we find that the additional amplitude of albedo change from the middle Holocene to the present caused by the very bright desert soils enhances the magnitude of the June-to-August precipitation change in the region of the present Sahara from 0.6 to 1.0 mm/day on average. We also find that albedo change has a larger effect on regional precipitation than changes in either the Earth's orbit or sea surface temperatures between 6,000 years ago and today. Simulated precipitation agrees rather well with present observations and mid Holocene reconstructions. Our results suggest that there may exist an important climate feedback from soil formation processes that has so far not been recognized.
ISSN:0930-7575
1432-0894
DOI:10.1007/s00382-005-0073-9