Marine Isotope Stage 11

Marine Isotope Stage 11, or MIS 11, was a warm period in Earth's climate history. It happened between 424,000 and 374,000 years ago and is part of what scientists call the geologic temperature record. This warm time is known as an interglacial period.

Scientists study interglacial periods like MIS 11 to learn more about how Earth’s climate changes. By looking at periods in the past, they can better understand what might happen in the future. MIS 11 is especially interesting because it can be compared to the current warm period we live in, called the Holocene. Comparing these times helps scientists predict future climate changes.

Characteristics

MIS 11 was a very warm and long time without ice ages, lasting longer than other similar periods in the past. During this time, the oceans were warmer, especially in colder areas, and the sea level was higher than it is today. Coral reefs grew more than usual, and some parts of the ocean lost some of their calcium-rich life forms. Scientists think MIS 11 was the warmest time without ice ages in the last half a million years.

Concentration of CO₂

Carbon dioxide levels during MIS 11 were likely similar to those before the industrial period, but not very high compared to other warm periods. One special thing about MIS 11 is that there wasn’t an early rise in carbon dioxide that usually happens when temperatures go up. This smaller amount of carbon dioxide happened because there was a lot of activity in the oceans early in MIS 11.

The long warm period during MIS 11 seems to have been influenced by how carbon dioxide levels and sunlight changed together. During times when certain patterns in Earth’s orbit were at their lowest, even small changes in sunlight could let carbon dioxide play a big role in controlling the climate.

Carbonate productivity

In shallow waters, big reefs like the Great Barrier Reef grew because more calcium carbonate was being made. This happened mostly in colder and warmer oceans far from the equator. The change happened because tiny sea creatures changed kinds when the water got warmer. This extra carbonate made in some places might be why we find less of it in other parts of the ocean, like the Indian and Pacific oceans. Another reason for lots of reefs in warm areas during this time could be that sea levels rose and covered land near the coasts.

Sea level & marine transgression

Beach deposits in Alaska, Bermuda and the Bahamas, as well as uplifted reef terraces in Indonesia, suggest that global sea level reached as much as twenty metres above today’s level. Records of δ¹⁸
O show changes that match this high sea level, but it’s hard to know if this was due to temperature or melting ice.

The higher sea level means that big ice sheets, like those in West Antarctica and Greenland, were smaller or even gone during this time. Deposits from Greenland suggest that much of south Greenland had no ice, leading to a sea level rise of about 4.5 to 6 metres around 410,000 to 400,000 years ago.

Astronomical features

MIS 11 was a special warm period between ice ages that happened around 424,000 to 374,000 years ago. It was longer than other warm periods because of changes in Earth’s orbit. These changes made the climate stay warm for a longer time and had fewer cold spells.

Scientists think MIS 11 might help us understand what could happen in the future with our climate. Some studies suggest that without human influence, our current warm period might have lasted longer, similar to MIS 11.