15.000 Jahre bewegte Klimageschichte in Nordafrika und Arabien

Im September 2018 erschien im Springer-Verlag das Buch “The Geology of the Arab World—An Overview“. Darin enthalten ist ein Kapitel von Sebastian Lüning und Fritz Vahrenholt zur Klimageschichte Nordafrikas und der Arabischen Halbinsel während der vergangenen 15.000 Jahre. Auf Basis umfangreicher Literaturrecherchen beschreiben die Autoren die Ergrünung sowie nachfolgende Austrocknung der Sahara im Verlauf des Holozäns. Zeitgleich zur Zunahme der Regenfälle stiegen auch die Temperaturen deutlich an und lagen einige Grad über dem Niveau der letzten 1000 Jahre. Das Holozäne Thermische Maximum (HTM) ist in der Region prägnant ausgeprägt und weist auf eine Synchronität zwischen der Klimageschichte Nordafrikas und Arabiens sowie der globalen Entwicklung hin. Hier der Abstract des Papers:

Holocene Climate Development of North Africa and the Arabian Peninsula
Holocene climate in North Africa and on the Arabian Peninsula has undergone major changes. In this contribution, we review hydroclimate and temperature changes in the region over the past 15,000 years by correlating and integrating all available case studies. A pronounced wet period corresponding to the ‘Green Sahara’ and its equivalent in Arabia commenced between 15,000 and 9000 years BP and ended sometime between 6500 and 3500 years BP, followed by arid conditions throughout the late Holocene. Start and end dates vary between locations, depending on local factors, climate amplifiers and chosen climate proxies, leading to a spatially and temporally complex distribution. Some studies show gradual transitions between the hydroclimatic states while other locations evidenced abrupt changes. The humid phase was triggered by a northward migration of the Intertropical Convergence Zone (ITCZ) due to orbital precession. The northernmost parts of North Africa and the Arabian Peninsula were not reached by the ITCZ. Here, increased early Holocene humidity may have been due to an intensification of southern Mediterranean winter rain and its deeper penetration southwards into the present-day desert areas. The early Holocene ‘Green Sahara’ forms part of a long series of wet periods that have occurred over the past hundred thousand to million years in North Africa and Arabia. Notably, climate models are still unable to match the observed hydroclimatic changes in a quantitative way. Simulated rainfall during the African Humid Period over the Sahara is not sufficient to sustain vegetation at a level seen in the palaeo record, indicating that processes such as vegetation and dust feedbacks still need to be refined. Sea surface temperatures in North Africa and Arabia during the early Holocene were generally one to several degrees C warmer than during the late Holocene. Warming began around 12,000 years BP and ended around 5000 years BP. The warm period generally coincided with the early Holocene wet phase in the region and is linked to the Holocene Thermal Maximum, an early Holocene period during which temperatures were globally elevated. The review suggests that the Holocene climate history of North Africa and Arabia is closely linked to the global development and that significant temperature changes have also occurred in subtropical climate belts.