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| Titel |
Expressions of climate perturbations in western Ugandan crater lake sediment records during the last 1000 years |
| VerfasserIn |
K. Mills, D. B. Ryves, N. J. Anderson, C. L. Bryant, J. J. Tyler |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 10, no. 4 ; Nr. 10, no. 4 (2014-08-27), S.1581-1601 |
| Datensatznummer |
250117029
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| Publikation (Nr.) |
 copernicus.org/cp-10-1581-2014.pdf |
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| Zusammenfassung |
Equatorial East Africa has a complex regional patchwork of climate regimes,
sensitive to climate fluctuations over a variety of temporal and spatial
scales during the late Holocene. Understanding how these changes are recorded
in and interpreted from biological and geochemical proxies in lake
sedimentary records remains a key challenge to answering fundamental
questions regarding the nature, spatial extent and synchroneity of climatic
changes seen in East African palaeo-records. Using a paired lake approach,
where neighbouring lakes share the same geology, climate and landscape, it
might be expected that the systems will respond similarly to external climate
forcing. Sediment cores from two crater lakes in western Uganda spanning the
last ~1000 years were examined to assess diatom community responses to
late Holocene climate and environmental changes, and to
test responses to
multiple drivers using redundancy analysis (RDA). These archives provide
annual to sub-decadal records of environmental change.
Lakes Nyamogusingiri and Kyasanduka appear to operate as independent systems
in their recording of a similar hydrological response signal via distinct
diatom records. However, whilst their fossil diatom records demonstrate an
individualistic, indirect response to external (e.g. climatic) drivers, the
inferred lake levels show similar overall trends and reflect the broader
patterns observed in Uganda and across East Africa. The lakes appear to be
sensitive to large-scale climatic perturbations, with evidence of a dry
Medieval Climate Anomaly (MCA; ca. AD 1000–1200). The diatom record from
Lake Nyamogusingiri suggests a drying climate during the main phase of the
Little Ice Age (LIA) (ca. AD 1600–1800),
whereas the diatom response from the shallower Lake Kyasanduka is more
complex (with groundwater likely playing a key role), and may be driven more
by changes in silica and other nutrients, rather than by lake level. The
sensitivity of these two Ugandan lakes to regional climate drivers breaks
down in ca. AD 1800, when major changes in the ecosystems appear to be a
response to increasing cultural impacts within the lake catchments, although
both proxy records appear to respond to the drought recorded across East
Africa in the mid-20th century.
The data highlight the complexity of diatom community responses to external
drivers (climate or cultural), even in neighbouring, shallow freshwater
lakes. This research also illustrates the importance of, and the need to move
towards, a multi-lake, multi-proxy landscape approach to understanding
regional hydrological change which will allow for rigorous testing of climate
reconstructions, climate forcing and ecosystem response models. |
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