Glacial Landscapes - How Cold Environments were Distributed in the Pleistocene Era

The distribution of cold environments over time has changed as global temperature has fluctuated.

When the temperature has dropped and more extensive areas have been covered in ice, these are known as glacial periods. The Earth is subject to periodic ice advances into lower latitudes and altitudes during this time. When the temperature then warms up again and the ice sheets melt back to their core regions, these time periods are known as interglacials.

Pleistocene epoch

During the Pleistocene epoch, ice coverage was much greater than can be seen today. This time period began 2.6 million years ago and ended approximately 11,800 years ago.

This time-period has seen frequent and regular global advances of ice, interspersed with warmer interglacials when ice retreated over an initial 41 000-year cycle and more recently a 100 000-year cycle. The present interglacial marks the end of the Pleistocene epoch with the rapid melting of extensive ice sheets.

In the northern hemisphere, the ice stretched from the Arctic southwards over Canada and just into the northern USA as far as New York. Over Europe, the ice extended over northern areas, including Scandinavia and large areas of the UK. Northern Russia was covered in ice and mountainous areas had a greater ice coverage than currently. Mountain ranges affected included the Alps, Himalayas and the Andes. The Antarctic ice sheet covered a much greater area than in present times (we are currently in the Holocene epoch, marking our current interglacial phase).

Suggested reasons for the repeated ice advances, followed by retreats, include the earth’s orbital change, sunspot activity, volcanic activity and ocean current changes:

Orbital change

Milankovitch Cycles describe the Earth changing its orbit around the sun. The orbit can vary from circular to elliptical and this can affect the amount of solar energy received by the earth. Less energy will result in a growth of glaciers and more energy causes an interglacial as ice sheets melt.

Milankovitch also suggested that that the Earth’s rotational axis can change. Typically, the Earth’s axis of rotation is tilted at 23.5 degrees from the vertical. However, this angle is liable to change a few degrees either way over time and, this affects the degree of seasonality upon the earth. The combination of orbital change coinciding with maximum/minimum axial tilt can shift the earth from a glacial to an interglacial phase – and back again.

Sunspot activity

Sunspot activity, whereby the sun releases additional energy from its surface has been shown to tie in with changes to the Earth’s climate.

The sun has been monitored by telescope since the 1600s and reductions in sun spot activity has a correlation with times when the Earth’s temperature dropped. An illustration of this occurred during The Little Ice Age (1650-1850), when northern Europe experienced longer winters, frozen seas and rivers and Alpine glaciers surged further down their valleys. This coincided with a period of lower solar sunspot activity.

Volcanic activity

Volcanic dust ejected during eruptions can have an impact on global temperature. Much of this dust is sent up into the lower atmosphere and has little impact as it is dispersed by wind. However, if the dust rises into the stratosphere it can stay there for weeks or months and this can cause global cooling. This cooling can lead to increased snow precipitation and the growth of ice frontiers.

Ocean current changes

Some scientists believe that changes to the Ocean Conveyor Belt will result in some areas of the world’s oceans not receiving their usual warm ocean currents, meaning that sea ice can increase. Similarly, during interglacials, the conveyor belt operates more effectively again and transfers warm water to polar areas, melting sea ice.