Younger Dryas: The Origin
The Younger Dryas (YD) stadial marks a significant period in the Earth's climatic history, noted for its extreme cold conditions in the northern hemisphere during the last stages of deglaciation. This period is crucial for understanding the evolution of glacial landforms, especially within the Tatra Mountains, where diverse glaciation patterns offer insights into the climatic conditions and landscape responses during the YD.
In the Tatra Mountains, the distinction between the High Tatras and the Western Tatras in terms of YD glaciation is noteworthy. The Western Tatras, being approximately 300-400 meters lower than the High Tatras, present a unique case where the development of clean-ice glaciers during the YD seems improbable. An exception is the Mułowy Kocioł cirque in the upper part of the Miętusia Valley within the Czerwone Wierchy massif, where the cirque's topography favored snow trapping and accumulation. This area features a prominent moraine, approximately 30-60 meters high, positioned on the cirque threshold at an elevation of 1800 meters above sea level and dated to the YD advance at 12.2 ka (Palacios et al., 2022).
Contrastingly, evidence of rock glacier development during the YD in the Western Tatras is less conclusive. The youngest rock glacier dated in the Smutná Valley suggests a YD age but is located at a significantly lower elevation compared to the High Tatras' YD rock glaciers. This discrepancy suggests that the Smutná Valley rock glacier may represent the prolonged activity of a glacier from the Oldest Dryas stadial, persisting through to the YD-Holocene transition.
The glaciation of the Tatra Mountains during the YD period was a complex process influenced by a combination of climatic and topographic factors. After glacier-free conditions during the Bølling–Allerød interstadial, YD glaciation redeveloped under a dry continental climate with relatively warm summers that limited glacier expansion. The distribution of YD moraines, no more than 600 meters from cirque backwalls, along with the development of rock glaciers, highlights the role of enhanced seasonality and winter cooling in shaping the glacial landscape. The marginal glaciation during the YD was strongly influenced by local topography, leading to underestimations of the climatic Equilibrium Line Altitude (ELA) using common hypsometric methods.
Cosmogenic exposure dating of YD moraines and rock glaciers in the Tatra Mountains suggests a stabilization period between 12.5-10.9 ka, with activity extending to the YD-Holocene transition but not beyond 10.4 ka. This period represents the final stage of cirque deglaciation in the Tatras, marking an end to significant glacier advances in the region during the Holocene.
In sum, the YD stadial's impact on the Tatra Mountains offers valuable insights into the climatic conditions and geomorphological processes of the last deglaciation phase. The distinct glaciation patterns observed in the High and Western Tatras underline the complex interplay between climate, topography, and glacial dynamics during this period.
