Session: Glacial Climates (LGM, Last deglaciation, Ice sheet uncertainties, Glacial-interglacial cycles)
Author: A.Kislov / email@example.com / M.V.lomonosov Moscow State University
The level fluctuations of closet lakes depend on regional-scale climate variations. Such lakes (especially such huge lake as the Caspian Sea (CS)) could be treated as natural labs, allows us to explore reaction of regional climate conditions to global climate changes.
During a long part of its history, the CS was a closet lake, separating by sill from the Black Sea. Sometimes, the CS level raised so high that the CS overflowed to the Black Sea. They were so-called the Early Khvalynian transgression (age ~35-25 ka BP) and the Late Khvalynian transgression (age ~17-12 ka BP). At the time of the Early Khvalynian transgression, the level of the CS was estimated up to 50 m above the modern state and sea area spread out far to north. The Late Khvalynian transgression was modest; the level of the CS achieved +27 m above the modern state. The main question concerning these events is what was source of additional water needed to providing these anomalies?
The Khvalynian phenomena did not occur due to high precipitations/river runoff over the East European Plain because model experiments (Sima et al., 2013) do not support this idea.
The contribution of melting water of the Scandinavian Ice Sheet is excluded too. Indeed, its boundary was located beyond the Volga River catchment area; the ice wall was permeable and the water could drain in the north direction (Sidorchuk et al., 2006).
The Khvalynian transgressions cannot be realized as the “stochastic anomaly”. Indeed, despite the CS level dynamics is represented by a system of undergoing random walk, the “super large” anomalies (like the Khvalynian transgressions) are impossible (Kislov, 2016).
Water volume was proposed to be increased due to an increase of the runoff coefficient due to permafrost (Sidorchuk et al., 2006). In addition, the melting of permafrost could provide a contribution to the runoff. So far, it is unclear whether this event was sufficient to ensure the Khvalynian transgressions.
Now we are faced with a paradox: «The event was, but it was inexplicable».