2 research outputs found
Hydroclimate in Africa during the Medieval Climate Anomaly
The Medieval Climate Anomaly (MCA) is a recognized period of distinct pre-industrial climate change, with a
core period of 1000–1200 CE. The field of palaeoclimatology has made major progress over the past 15 years
during which a great number of high- and medium-resolution case studies were published, reconstructing climate
change of the past millennia. In many parts of the world, regional data coverage has now reached a point
which allows compiling palaeoclimate maps for well-defined time intervals. Here we present hydroclimatic trend
maps for the MCA in Africa based on 99 published study locations. Key hydroclimatic proxy curves are visualized
and compared in a series of 16 correlation panels. Proxy types are described and possible issues discussed. Based
on the combined MCA dataset, temporal and spatial trends are interpreted and mapped out. Three areas have
been identified in Africa in which rainfall seems to have increased during the MCA, namely Tunisia, western
Sahel and the majority of southern Africa. At the same time, a reduction in precipitation occurred in the rest of
Africa, comprising of NW and NE Africa, West Africa, Eastern Africa and the Winter Rainfall Zone of South
Africa. MCA hydroclimate change in Africa appears to have been associated with characteristic phases of ocean
cycles, as also supported by modern climate observations. Aridity in Morocco typically coincides with the positive
phase of the North Atlantic Oscillation (NAO), whilst increased rainfall in the western Sahel is often
coupled to the positive phase of the Atlantic Multidecadal Oscillation (AMO). Reduction in rainfall in the region
Gulf of Aden/southern Red Sea to Eastern Africa could be linked to a negative Indian Ocean Dipole (IOD) or a
derived long-term equivalent Indian Ocean cycle parameter. The Intertropical Convergence Zone (ITCZ) appears
to have been shifted pole-wards during the MCA, for both the January and July positions. MCA hydroclimate
mapping revealed major data gaps in the Sahara, South Sudan, Somalia, Central African Republic, Democratic
Republic of Congo, Angola, northern Mozambique, Zambia and Zimbabwe. Special efforts are needed to fill these
gaps, e.g. through a dedicated structured research program in which new multiproxy datasets are created, based
on the learnings from previous African MCA studies