Latitudinal linkages in late Holocene moisture-balance variation
Marked regional correspondence exists both within and between high and low latitude regions in Holocene moisture-balance changes at millennial and century time scales. Apparent regional variation in the principal Holocene trends of monsoon intensity across the NH subtropics, from a gradual response...
| Main Authors: | , |
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| Other Authors: | , |
| Format: | Book Part |
| Language: | English |
| Published: |
Wiley-Blackwell
2008
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| Subjects: | |
| Online Access: | https://biblio.ugent.be/publication/701038 http://hdl.handle.net/1854/LU-701038 https://biblio.ugent.be/publication/701038/file/4134542 |
| Summary: | Marked regional correspondence exists both within and between high and low latitude regions in Holocene moisture-balance changes at millennial and century time scales. Apparent regional variation in the principal Holocene trends of monsoon intensity across the NH subtropics, from a gradual response to precessional insolation forcing to a succession of millennial-scale climate swings, must have both a real regional climate component and a component dependent on the archive or proxy indicator recording the climate change. Consistent century-scale water-table changes in Northwest Europe reconstructed from peatlands have occurred in synchrony with lake-level changes in west-central Europe, and somewhat less clearly with mass balance changes of Alpine glaciers. The relative magnitude of individual events is archive-dependent and regionally diverse. Some episodes of high lake level and aquifers (at ~3400, 2750, 1250 and 700 BP) and inferred cool weather correspond to periods of reduced solar activity, suggesting a causative link. However the anomalies are not proportional to the proposed forcing, and some hydrological events have no equivalent in the record of solar activity. Records from Iceland to tropical Africa reveal a pronounced shift to wetter conditions ~1250 AD, terminating a warm and/or dry Medieval Optimum with the onset of the most recent North Atlantic cool event. Strong inverse correlation between British peat surface wetness and moisture balance in central equatorial Africa at century time scales over the last 5000 years suggest that north Atlantic cool episodes (not all of which are recorded as drift-ice events) affected cross-equatorial heat transport and the mean position of the Intertropical Convergence Zone. During the main phase of the Little Ice Age (~1550 to 1800 AD) the current west-to-east gradient across equatorial Africa from a humid climate in the west to a semi-arid climate in the east was reduced or possibly reversed. This modification of geographical climate patterns is a reflection of ... |
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