Details

Autor(en) / Beteiligte

• Chandan, Deepak
• Peltier, W. Richard

Titel

African Humid Period Precipitation Sustained by Robust Vegetation, Soil, and Lake Feedbacks

Ist Teil von

• Geophysical research letters, 2020-11, Vol.47 (21), p.n/a

Ort / Verlag

Washington: John Wiley & Sons, Inc

Erscheinungsjahr

2020

Link zum Volltext

Quelle

Wiley Online Library - AutoHoldings Journals

Beschreibungen/Notizen

• The African Humid Period (∼11,000–5,000 years before present) was the most recent of several precessionally paced wet intervals during which an increase in the Northern Hemisphere summer incoming solar radiation intensifies the West African Monsoon leading to dramatic changes over northern Africa. However, insolation anomaly alone is not sufficient and feedbacks are essential for further amplification of the monsoon. The most significant feedbacks derive from the land surface, arising from changes to vegetation, soil properties, and distribution of surface water. We show that in contrast to previous studies that have explored the individual impacts of these feedbacks, a modern climate model yields a much greater increase in precipitation in response to their collective effect. Agreement with proxies is improved while the desert‐steppe transition is pushed further northward than in any previous study. In the West African Sahel, intensities of summer daily mean and extreme precipitation increase by 150% and 90%, respectively. Plain Language Summary From approximately 11,000 to 5,000 years before present, the summer monsoon over northern Africa was considerably stronger than what it is today and as such this period has come to be called the African Humid Period. As a result of this, lakes, wetlands, and rivers sprung up in the now arid regions of northern Africa and made it possible for vegetation to migrate northward which “greened the Sahara.” It is widely understood that the greater amount of summer solar radiation impinging on this region, arising from a modest variation in the Earth's orbital configuration at that time, kick‐started this intensification. However, while this may have triggered the strengthening of the monsoon, it was not by itself sufficient to intensify it to the degree suggested by proxies that register the strength of palaeomonsoons. The interaction between the atmosphere and the greener and wetter land surface could have further invigorated the monsoon, but based on the results from modeling experiments performed thus far, it has been thought that even this additional interaction is not sufficient. Here, we show that land‐atmosphere interaction does however have the potential to strengthen the monsoon sufficiently to obtain agreement with proxy estimates. Key Points Thus far, few studies have explored the combined effect of feedbacks from mid‐Holocene vegetation, soil, and lakes on precipitation We find much greater impact on precipitation from the combined feedbacks than previously reported Agreement with proxies improves with feedbacks and modeled precipitation can sustain prescribed vegetation over all of northern Africa