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What were the Yoldia Sea and Ancylus Lake?

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Map showing the physical features, major cities, and national boundaries around the Baltic Sea, North Sea, and English Channel regions of northern and western Europe. The map highlights coastal countries including the United Kingdom, Norway, Denmark, Germany, the Netherlands, Belgium, France, Sweden, Finland, Estonia, Latvia, Lithuania, Poland, and Russia, with sea depths indicated and key islands, peninsulas, and underwater trenches labeled. — Baltic Sea The Baltic Sea, the North Sea, and the English Channel.

The Yoldia Sea and Ancylus Lake were successive stages in the development of the Baltic Sea as the Scandinavian ice sheet retreated at the end of the Pleistocene Epoch.1

Yoldia Sea: Formed by glacial meltwater around 7700 BCE, this body of water stretched eastward from the present-day Skagerrak across southern Sweden to the area of Lake Ladoga, beyond the Gulf of Finland.1
Ancylus Lake: Approximately 1,000 years after the Yoldia Sea stage, as the remaining stagnant ice in northern Sweden disappeared, the region transitioned into the freshwater Ancylus Lake. This lake extended from Arctic Sweden and Finland down to the present-day southern Baltic region.1

These stages represent the shifting geography of northern Europe following the removal of the massive weight of glaciers, which also triggered long-term land uplift in the surrounding lowland regions.1