From the geological data, reviewed by Polyak et al (2010) he concluded that the history of Arctic sea ice is closely linked with climate changes driven primarily by greenhouse and orbital forcing and associated feedbacks. A link made when considering the Arctic amplification. Based on proxy records sea ice appeared as early as 47Ma, coinciding with a long term climatic cooling following the Paleocene-Eeocene Thermal Maximum which led to the formation of large ice sheets. At least 13-14Ma year round sea ice occurred in relation to the progression of the aforementioned cool period. This period has been described as similar to that of last decade. Sea ice then slowly declined until the onset of Quaternary glaciations in the Northern Hemisphere after about 3Ma. Quaternary interglacials and interstitials may have been seasonally ice free, as is the case at the moment. Evidence for the importance of precession as a determinant in sea ice extent has been established. Which also links into the previously mentioned alebedo feed back relationship. Orbital variation alone has been identified as not been a sole control revealing reductions as more complex than these variations alone. This is highlighted by high resolution Holocene proxies. There are many uncertainties as the proxies are sparse however several critical ideas can be carried forward furthering modern understanding of sea ice reduction.
Suborbital time scales and ice distributions varied in the Holocene, but no evidence has been found to suggest pan-Arctic fluctuations in sea ice extent. Oscillation in the extent have been identified, however reductions in the extent even close to what has been observed over the last several decades has not been experienced for at the least the last few thousand years. The magnitude and scale of contemporary ice loss can thus said to be anomalous in comparison submillenial evidence.
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