Antje Wegwerth

Black Sea temperature response to glacial millennial-scale climate variability

The Eurasian inland propagation of temperature anomalies during glacial millennial-scale climate variability is poorly understood, but this knowledge is crucial to understanding hemisphere-wide atmospheric teleconnection patterns and climate mechanisms. Based on biomarkers and geochemical paleothermometers, a pronounced continental temperature variability between 64,000 and 20,000 years ago, coinciding with the Greenland Dansgaard-Oeschger cycles, was determined in a well-dated sediment record from the formerly enclosed Black Sea. Cooling during Heinrich events was not stronger than during other stadials in the Black Sea. This is corroborated by modeling results showing that regular Dansgaard-Oeschger cycles penetrated deeper into the Eurasian continent than Heinrich events. The pattern of coastal ice-rafted detritus suggests a strong dependence on the climate background state, with significantly milder winters during periods of reduced Eurasian ice sheets and an intensified meridional atmospheric circulation.

Environmental and Climate Dynamics During the Last Two Glacial Terminations and Interglacials in the Black Sea/Northern Anatolian Region

This study provides the first detailed multi-proxy paleoenvironmental reconstructions of changes in the aquatic and terrestrial ecosystems during the Holocene, Eemian and the last two glacial/interglacial transitions (Terminations I and II) by studying sediment cores from the southeastern Black Sea and stalagmite studies from Sofular Cave in northwestern Anatolia. The terrestrial proxies document gradual changes from late glacial cold/arid conditions in northern Anatolia, dominated by steppe vegetation, to warm/humid forest dominated landscapes characteristic for interglacial periods. The Holocene and Eemian, however, developed differently, with warmer and moister conditions prevailing during the Eemian. Major fluctuations in the hydrological state of the Black Sea are closely linked to changes of terrestrial environments. Disrupted by large melt water pulses from the disintegrating Fennoscandian Ice Sheet, the limnic glacial Black Sea environment becomes more productive during the postglacial warming. Global sea-level rise finally reconnects the hydrological increasingly active Black Sea basin with the Mediterranean Sea leading to the development of marine, for the Eemian even fully marine, conditions with a stratified water column and sapropelic sedimentation.