The Eemian Period was a significant warm phase in Earth’s ancient past, offering scientists a natural window into how our planet’s systems respond to warmer conditions. This interglacial period, characterized by temperatures and sea levels higher than today, provides valuable insights into Earth’s long-term climate sensitivities and the behavior of its major ice sheets.
What Was the Eemian Period?
The Eemian Period, also known as the Last Interglacial, occurred approximately 129,000 to 116,000 years ago. It was the most recent warm interval between two extensive glacial periods, directly following the Saalian Glacial Stage and preceding the Weichsel Glacial Stage, which was the last major ice age before our current Holocene interglacial.
This geological epoch is recognized globally, though it has different regional names, such as the Ipswichian in Britain or the Riss-Würm interglacial in the Alps. Its fundamental characteristic was a sustained period of warmth, providing a contrast to the colder glacial conditions that typically dominate Earth’s recent geological history. The Eemian Period spanned about 13,000 years.
Climate and Environment of the Eemian
During the Eemian Period, global temperatures were generally warmer than pre-industrial levels, with average temperatures 1-2°C higher. Certain Arctic regions experienced even more substantial warming, with temperatures estimated to be 4-5°C above present levels. Specifically, northwestern Greenland saw a local warming of approximately 8.5 ± 2.5°C compared to pre-industrial times.
These elevated temperatures led to significantly higher global sea levels, estimated to be between 6 and 9 meters above current levels. The primary contributors to this sea-level rise were the melting of polar ice sheets, including a substantial disintegration of the West Antarctic Ice Sheet and a considerable reduction in the Greenland Ice Sheet. Marine deposits from the Eemian indicate extensive coastal changes.
The warmer climate supported a rich and diverse range of flora and fauna. In Europe, fossil records reveal the presence of varied mammalian species, including horses, bison, different types of elephants, and cave bears. Vegetation zones shifted poleward, leading to the expansion of forests and grasslands in many regions. Pollen analysis indicates a succession from pioneer vegetation like birch and pine to deciduous forests with oak and hazel, later transitioning to yew, hornbeam, and spruce before a return to pine and birch towards the end of the period. Atmospheric carbon dioxide concentrations during the Eemian were around 280 parts per million, which is lower than today’s levels.
Why the Eemian Matters Today
The Eemian Period serves as a natural analogue for understanding Earth’s response to warming climates. Studying this past warm interval provides insights into the long-term behavior of Earth’s systems under conditions similar to or warmer than present-day. This historical perspective helps assess the potential future impacts of current global warming.
The period offers lessons regarding ice sheet stability and sea-level rise. The significant retreat of the Greenland and West Antarctic ice sheets during the Eemian, contributing to meters of sea-level rise, provides a reference for potential ice loss in a warming world. This past behavior informs projections about how quickly modern ice sheets might melt.
Eemian studies also shed light on ecosystem shifts and climate feedback mechanisms. While Eemian warming was primarily driven by changes in Earth’s orbital parameters rather than greenhouse gas concentrations, it demonstrates how ecosystems respond to sustained warmth. Understanding these past responses helps refine climate models and improve their ability to predict future environmental changes.
Unlocking Eemian Secrets
Scientists reconstruct the Eemian Period through the analysis of various paleoclimate records. Ice cores, drilled from the vast ice sheets of Greenland and Antarctica, contain trapped air bubbles and layers of ice that provide direct evidence of past atmospheric composition, including greenhouse gas levels, and temperatures. The NEEM ice core from Greenland, for instance, has offered detailed insights into Eemian temperatures in the Arctic.
Marine sediment cores, extracted from ocean and lake beds, offer another rich source of information. These cores preserve layers of sediment containing fossilized remains of microscopic organisms, pollen, and other environmental indicators. Analyzing these components allows researchers to reconstruct past sea levels, ocean circulation patterns, and the types of flora that flourished on land.
Pollen analysis, specifically, helps identify the dominant vegetation types and track shifts in plant distributions, providing a picture of past ecosystems and climate zones. Combined, these diverse lines of evidence allow scientists to piece together a comprehensive understanding of the Eemian’s climate and environmental characteristics.