A 23,000 yr pollen record from Lake Rukwa (8°S, SW Tanzania): New data on vegetation dynamics and climate in Central Eastern Africa

2005 ◽  
Vol 137 (3-4) ◽  
pp. 147-162 ◽  
Author(s):  
Annie Vincens ◽  
Guillaume Buchet ◽  
David Williamson ◽  
Maurice Taieb
Keyword(s):  
Vegetation Dynamics ◽  
Eastern Africa ◽  
Pollen Record ◽  
Central Eastern

scholarly journals Key Factors of Precipitation Stable Isotope Fractionation in Central-Eastern Africa and Central Mediterranean

Geosciences ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 337 ◽  
Author(s):  
Charles M. Balagizi ◽  
Marcello Liotta
Keyword(s):  
Isotope Fractionation ◽  
Hydrological Cycle ◽  
Global Scale ◽  
Vapor Condensation ◽  
Eastern Africa ◽  
Tropical Region ◽  
Central Mediterranean ◽  
Mild Winter ◽  
Stable Isotope Fractionation ◽  
Central Eastern

The processes of isotope fractionation in the hydrological cycle naturally occur during vapor formation, vapor condensation, and moisture transportation. These processes are therefore dependent on local and regional surface and atmospheric physical features such as temperature, pressure, wind speed, and land morphology, and hence on the climate. Because of the strong influence of climate on the isotope fractionation, latitudinal and altitudinal effects on the δ18O and δ2H values of precipitation at a global scale are observed. In this study, we present and compare the processes governing precipitation isotope fractionation from two contrasting climatic regions: Virunga in Central-Eastern Africa and the Central Mediterranean (Stromboli and Sicily, Italy). While Virunga is a forested rainy tropical region located between Central and Eastern Africa, the Mediterranean region is characterized by a rainy mild winter and a dry hot summer. The reported δ18O and δ2H dataset are from precipitation collected on rain gauges sampled either on a monthly or an approximately bimonthly basis and published in previous papers. Both regions show clearly defined temporal and altitudinal variations of δ18O and δ2H, depending on precipitation amounts. The Central Mediterranean shows a clear contribution of local vapor forming at the sea–air interface, and Virunga shows a contribution from both local and regional vapor. The vapor of Virunga is from two competing sources: the first is the continental recycled moisture from soil/plant evaporation that dominates during the rainy season, and the second is from the East African Great Lakes evaporation that dominates during the dry season.

Vegetation dynamics and climate variability during the Holsteinian interglacial based on a pollen record from Dethlingen (northern Germany)

2010 ◽  
Vol 29 (23-24) ◽  
pp. 3298-3307 ◽  
Author(s):  
Andreas Koutsodendris ◽  
Ulrich C. Müller ◽  
Jörg Pross ◽  
Achim Brauer ◽  
Ulrich Kotthoff ◽  
...  
Keyword(s):  
Climate Variability ◽  
Vegetation Dynamics ◽  
Pollen Record ◽  
Northern Germany

scholarly journals Orbital and millennial-scale environmental changes between 64 and 25 ka BP recorded in Black Sea sediments

2013 ◽  
Vol 9 (5) ◽  
pp. 5439-5477
Author(s):  
L. S. Shumilovskikh ◽  
D. Fleitmann ◽  
N. R. Nowaczyk ◽  
H. Behling ◽  
F. Marret ◽  
...  
Keyword(s):  
Black Sea ◽  
Vegetation Dynamics ◽  
Environmental Changes ◽  
Glacial Refugia ◽  
The Black Sea ◽  
Carbonate Content ◽  
Pollen Record ◽  
Freshwater Algae ◽  
Climate Conditions ◽  
Black Sea Region

Abstract. High-resolution pollen and dinoflagellate cyst records from marine sediment core 25-GC1 were used to reconstruct vegetation dynamics in Northern Anatolia and surface conditions of the Black Sea between 64 and 25 ka BP. During this period, the dominance of Artemisia in the pollen record indicates a steppe landscape and arid climate conditions. However, the presence of temperate and warm-temperate arboreal pollen suggests the existence of glacial refugia in Northern Anatolia. A general cooling trend towards 25 ka BP is evidenced by the decrease of Quercus and increase of Pinus. There is evidence of orbital-driven vegetation dynamics in Northern Anatolia during 64–25 ka BP with spread of steppe during precession minima (insolation maxima) and development of forests during precession maxima (insolation minima). Dansgaard–Oeschger (D–O) events are characterized by a marked increase in temperate tree pollen, indicating a spread of forests due to warm and wet conditions in Northern Anatolia. The dominance of Pyxidinopsis psilata and Spiniferites cruciformis in the dinocyst record indicates a rather brackish Black Sea during the last glacial period. The decrease of marine indicators (marine dinocysts, acritachs) at ~ 54 ka BP and increase of freshwater algae (Pediastrum, Botryococcus) from 32 to 25 ka BP reveals freshening of the Black Sea surface water, related to orbital-driven arid/humid phases in the region, influencing hydrology and level changes of the Black Sea. D–O interstadials are characterized by high dinocyst concentrations and calcium carbonate content, as a result of an increase in primary productivity in the Black Sea. Heinrich events show a similar impact on the environment in Northern Anatolia/Black Sea region as D–O stadials.

scholarly journals Orbital- and millennial-scale environmental changes between 64 and 20 ka BP recorded in Black Sea sediments

2014 ◽  
Vol 10 (3) ◽  
pp. 939-954 ◽  
Author(s):  
L. S. Shumilovskikh ◽  
D. Fleitmann ◽  
N. R. Nowaczyk ◽  
H. Behling ◽  
F. Marret ◽  
...  
Keyword(s):  
Black Sea ◽  
Vegetation Dynamics ◽  
Environmental Changes ◽  
The Black Sea ◽  
Carbonate Content ◽  
Phase Lag ◽  
Pollen Record ◽  
Freshwater Algae ◽  
Atlantic Sector ◽  
Climate Conditions

Abstract. High-resolution pollen and dinoflagellate cyst records from sediment core M72/5-25-GC1 were used to reconstruct vegetation dynamics in northern Anatolia and surface conditions of the Black Sea between 64 and 20 ka BP. During this period, the dominance of Artemisia in the pollen record indicates a steppe landscape and arid climate conditions. However, the concomitant presence of temperate arboreal pollen suggests the existence of glacial refugia in northern Anatolia. Long-term glacial vegetation dynamics reveal two major arid phases ~64–55 and 40–32 ka BP, and two major humid phases ~54–45 and 28–20 ka BP, correlating with higher and lower summer insolation, respectively. Dansgaard–Oeschger (D–O) cycles are clearly indicated by the 25-GC1 pollen record. Greenland interstadials are characterized by a marked increase in temperate tree pollen, indicating a spread of forests due to warm/wet conditions in northern Anatolia, whereas Greenland stadials reveal cold and arid conditions as indicated by spread of xerophytic biomes. There is evidence for a phase lag of ~500 to 1500 yr between initial warming and forest expansion, possibly due to successive changes in atmospheric circulation in the North Atlantic sector. The dominance of Pyxidinopsis psilata and Spiniferites cruciformis in the dinocyst record indicates brackish Black Sea conditions during the entire glacial period. The decrease of marine indicators (marine dinocysts, acritarchs) at ~54 ka BP and increase of freshwater algae (Pediastrum, Botryococcus) from 32 to 25 ka BP reveals freshening of the Black Sea surface water. This freshening is possibly related to humid phases in the region, to connection between Caspian Sea and Black Sea, to seasonal freshening by floating ice, and/or to closer position of river mouths due to low sea level. In the southern Black Sea, Greenland interstadials are clearly indicated by high dinocyst concentrations and calcium carbonate content, as a result of an increase in primary productivity. Heinrich events show a similar impact on the environment in the northern Anatolia/Black Sea region as Greenland stadials.

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