Interglacial - Interglacial Optimum

Interglacial Optimum

An interglacial optimum, or climatic optimum of an interglacial, is the period within an interglacial that experienced the most 'favourable' climate that occurred during that interglacial, often during the middle part. The climatic optimum of an interglacial follows, and is followed by, phases that are within the same interglacial and that experienced a less favourable climate (but nevertheless a 'better' climate than during the preceding/succeeding glacials). During an interglacial optimum, sea levels rise to their highest values, but not necessarily exactly at the same time as the climatic optimum.

In the present interglacial, the Holocene, the climatic optimum occurred during the Subboreal (5 to 2.5 ka BP, which corresponds to 3000 BC-500 BC) and Atlanticum (9 to 5 ka, which corresponds to roughly 7000 BC-3000 BC). Our current climatic phase following this climatic optimum is still within the same interglacial (the Holocene). This warm period was followed by a gradual decline until about 2,000 years ago, with another warm period until the Little Ice Age (1250-1850).

The preceding interglacial optimum occurred during the Late Pleistocene Eemian Stage, 131–114 ka. During the Eemian the climatic optimum took place during pollen zone E4 in the type area (city of Amersfoort, Netherlands). Here this zone is characterized by the expansion of Quercus (Oak), Corylus (Hazel), Taxus, Ulmus (Elm), Fraxinus (Ash), Carpinus (Hornbeam), and Picea (Spruce). During the Eemian Stage sea level was about 8 meters higher than today and the water temperature of the North Sea was c. 2°C higher than at present.