Important Notes from the NOAA article:
Many times in the past continental ice sheets (glaciers) have advanced and retreated.
The most recent glacial period was between 120 kya to 11.5 kya. Since 11.5 kya the earth has been in an interglacial (warming) period known as the “Holocene.” The Holocene is part of the Quaternary Period which began 1.8 mya.
When more water is locked up in ice sea levels are lower. In contrast, when less water is locked up in ice, as it is today, sea levels are higher.
Glacial periods tend to be colder, dustier, and DRIER than interglacial periods. Popular conception is that glacial periods are wetter with more snow but this is a myth.
Causes of glacial-interglacial cycles is connected to the Earth’s orbit which has varied and changed through time. Changes in the planet’s orbit changes the amount of solar radiation (sunlight) received by the Earth each season.
Inter-glacial periods have higher temps. Summer solar radiation in the Northern Hemisphere tends to be more intense, meaning higher summer temps.
Since the Middle Quaternary period glacial and interglacial cycles have a frequency of about 100,000 years.
Temp variations in Antarctica are in phase with solar radiation changes in the high northern latitudes. Solar radiation changes in the high SOUTHERN latitudes near Antarctica are actually out of phase with temp changes. For example, the coldest period during the last ice age that ended 11.5 kya occurred at about the time the region was experiencing a peak in local sunshine! What this means is that ice sheet growth in the Northern Hemisphere has an important influence on climate globally!
Glacial periods tend to end abruptly. Warming at the end of glacial periods tends to happen more abruptly than the increase in solar insolation. Atmospheric CO2 is one reason for this. During glacial periods CO2 in the atmosphere decreases because CO2 during such periods is store in the deep ocean. In contrast, during interglacial periods CO2 increases in the atmosphere as deep oceans release stored CO2. Lower CO2 levels weaken the Greenhouse Effect and maintain lower temps. When the oceans release stored CO2 it increases the Greenhouse Effect which contributes to further global warming.
I must note the ice core samples taken a few years ago by the University of Indiana et al also revealed that glaciations also begin suddenly!
The below chart showing glacials and interglacials over the past 680,000 years is from:
ADDITIONAL POSTS REGARDING PALEOCLIMATES CAN BE FOUND AT:
Paleoclimates: The Carboniferous Period—https://rperon1017blog.wordpress.com/2017/01/27/paleoclimate-the-carboniferous-period/
Paleoclimates: The Cenozoic Era — https://rperon1017blog.wordpress.com/2017/01/30/paleoclimate-the-cenozoic-era/
Man, Climate, & Evolution— https://rperon1017blog.wordpress.com/2017/01/31/man-climate-and-evolution/