Geoscience Reference
In-Depth Information
10
Arctic Paleoclimates
Overview
Global and Arctic climates have varied widely in the past. On time
scales of tens to hundreds of millions of years, these changes were at
least partly a result of the shifting configurations of land and ocean and
mountain-building events associated with continental drift. Even though
it appears that the earth has experienced ice ages in many periods of its
history, including the Neoproterozoic, 710 and 640 million years before
present (hereafter abbreviated as Ma), the Ordovician and Silurian (460
and 430 Ma), and the Carboniferous and Permian (350 and 250 Ma), we
know few details about these events. Much more is known of global and
Arctic climates during the Quaternary. The Quaternary, comprised of the
Pleistocene and Holocene epochs, extends from about 2.6 million years
ago to the present.
The Ice Ages of the Pleistocene captivate the imagination. The
Pleistocene was characterized by many glacial advances and retreats.
Although the climate of the Arctic varied with these glacial cycles, which
seem to have been triggered by periodicities in the earth's axial tilt, the
eccentricity of its orbit about the sun and the precession of the equinoxes,
collectively known as Milankovitch cycles, high-latitude processes, such
as ice-albedo feedbacks and deepwater formation in the northern North
Atlantic, likely contributed to change. The most complete information on
the Pleistocene is for the last glacial cycle, extending from the Holocene
back to the Eemian Interglacial, (130,000-115,000 years ago; 130-115
ka). Climates during the last glacial cycle were extremely variable,
featuring Dansgaard-Oeschger (D-O) cycles, characterized by rapid
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