Simulated range of mid-Holocene precipitation changes from extended lakes and wetlands over North Africa
<p>Enhanced summer insolation over North Africa induced a monsoon precipitation increase during the mid-Holocene, about 6000 years ago, and led to a widespread expansion of lakes and wetlands in the present-day Sahara. This expansion of lakes and wetlands is documented in paleoenvironmental se...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2022-05-01
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| Series: | Climate of the Past |
| Online Access: | https://cp.copernicus.org/articles/18/1035/2022/cp-18-1035-2022.pdf |
| _version_ | 1818211427578544128 |
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| author | N. F. Specht M. Claussen M. Claussen T. Kleinen |
| author_facet | N. F. Specht M. Claussen M. Claussen T. Kleinen |
| author_sort | N. F. Specht |
| collection | DOAJ |
| description | <p>Enhanced summer insolation over North Africa induced a monsoon precipitation increase during the mid-Holocene, about 6000 years ago, and led to a widespread expansion of lakes and wetlands in the present-day Sahara. This expansion of lakes and wetlands is documented in paleoenvironmental sediment records, but the spatially sparse and often discontinuous sediment records provide only a fragmentary picture. Previous simulation studies prescribed either a small lake and wetland extent from reconstructions or focused on documented mega-lakes only to investigate their effect on the mid-Holocene climate. In contrast to these studies, we investigate the possible range of mid-Holocene precipitation changes in response to a small-lake extent and a potential maximum lake and wetland extent.</p>
<p>Our study shows that during the summer monsoon season, the African rain belt is shifted about 2 to 7<span class="inline-formula"><sup>∘</sup></span> farther north in simulations with a maximum lake or wetland extent than in simulations with a small lake extent. This northward extent is caused by a stronger and prolonged monsoon rainfall season over North Africa which is associated with an increased monsoon precipitation over the southern Sahara and an increased precipitation from tropical plumes over the northwestern Sahara. Replacing lakes with vegetated wetlands causes an enhanced precipitation increase, which is likely due to the high surface roughness of the wetlands. A moisture budget analysis reveals that both lakes and wetlands cause a local precipitation increase not only by enhanced evaporation but also by a stronger inland moisture transport and local moisture recycling to the south of Lake Chad and the west Saharan lakes. Analysis of the dynamic response shows that lakes and wetlands cause a circulation response inverse to the one associated with the Saharan heat low. Depending on the latitudinal position of the lakes and wetlands, they predominantly cause a northward shift or a decay of the African Easterly Jet. These results indicate that the latitudinal position of the lakes and wetlands strongly affects the northward extension of the African summer monsoon.</p> |
| first_indexed | 2024-12-12T05:32:20Z |
| format | Article |
| id | doaj.art-11e66d94a78d4396a6110cee8d7016e1 |
| institution | Directory Open Access Journal |
| issn | 1814-9324 1814-9332 |
| language | English |
| last_indexed | 2024-12-12T05:32:20Z |
| publishDate | 2022-05-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Climate of the Past |
| spelling | doaj.art-11e66d94a78d4396a6110cee8d7016e12022-12-22T00:36:16ZengCopernicus PublicationsClimate of the Past1814-93241814-93322022-05-01181035104610.5194/cp-18-1035-2022Simulated range of mid-Holocene precipitation changes from extended lakes and wetlands over North AfricaN. F. Specht0M. Claussen1M. Claussen2T. Kleinen3Max Planck Institute for Meteorology, Bundesstrasse 53, 20146 Hamburg, GermanyMax Planck Institute for Meteorology, Bundesstrasse 53, 20146 Hamburg, GermanyMeteorological Institute, Centrum für Erdsystemforschung und Nachhaltigkeit (CEN), Universität Hamburg, Bundesstrasse 55, 20146 Hamburg, GermanyMax Planck Institute for Meteorology, Bundesstrasse 53, 20146 Hamburg, Germany<p>Enhanced summer insolation over North Africa induced a monsoon precipitation increase during the mid-Holocene, about 6000 years ago, and led to a widespread expansion of lakes and wetlands in the present-day Sahara. This expansion of lakes and wetlands is documented in paleoenvironmental sediment records, but the spatially sparse and often discontinuous sediment records provide only a fragmentary picture. Previous simulation studies prescribed either a small lake and wetland extent from reconstructions or focused on documented mega-lakes only to investigate their effect on the mid-Holocene climate. In contrast to these studies, we investigate the possible range of mid-Holocene precipitation changes in response to a small-lake extent and a potential maximum lake and wetland extent.</p> <p>Our study shows that during the summer monsoon season, the African rain belt is shifted about 2 to 7<span class="inline-formula"><sup>∘</sup></span> farther north in simulations with a maximum lake or wetland extent than in simulations with a small lake extent. This northward extent is caused by a stronger and prolonged monsoon rainfall season over North Africa which is associated with an increased monsoon precipitation over the southern Sahara and an increased precipitation from tropical plumes over the northwestern Sahara. Replacing lakes with vegetated wetlands causes an enhanced precipitation increase, which is likely due to the high surface roughness of the wetlands. A moisture budget analysis reveals that both lakes and wetlands cause a local precipitation increase not only by enhanced evaporation but also by a stronger inland moisture transport and local moisture recycling to the south of Lake Chad and the west Saharan lakes. Analysis of the dynamic response shows that lakes and wetlands cause a circulation response inverse to the one associated with the Saharan heat low. Depending on the latitudinal position of the lakes and wetlands, they predominantly cause a northward shift or a decay of the African Easterly Jet. These results indicate that the latitudinal position of the lakes and wetlands strongly affects the northward extension of the African summer monsoon.</p>https://cp.copernicus.org/articles/18/1035/2022/cp-18-1035-2022.pdf |
| spellingShingle | N. F. Specht M. Claussen M. Claussen T. Kleinen Simulated range of mid-Holocene precipitation changes from extended lakes and wetlands over North Africa Climate of the Past |
| title | Simulated range of mid-Holocene precipitation changes from extended lakes and wetlands over North Africa |
| title_full | Simulated range of mid-Holocene precipitation changes from extended lakes and wetlands over North Africa |
| title_fullStr | Simulated range of mid-Holocene precipitation changes from extended lakes and wetlands over North Africa |
| title_full_unstemmed | Simulated range of mid-Holocene precipitation changes from extended lakes and wetlands over North Africa |
| title_short | Simulated range of mid-Holocene precipitation changes from extended lakes and wetlands over North Africa |
| title_sort | simulated range of mid holocene precipitation changes from extended lakes and wetlands over north africa |
| url | https://cp.copernicus.org/articles/18/1035/2022/cp-18-1035-2022.pdf |
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