Editing Polar ice cap (section)

===Historical cases===
Over the past several decades, Earth's polar ice caps have gained significant attention because of the alarming decrease in land and sea ice. [[NASA]] reports that since the late 1970s, the [[Arctic]] has lost an average of 20,800 square miles (53,900 square kilometres) of sea ice per year while the [[Antarctic]] has gained an average of 7,300 square miles (18,900&nbsp;km<sup>2</sup>) of sea ice per year. At the same time, the Arctic has been losing around 50 cubic kilometres (gigatons) of land ice per year, almost entirely from Greenland's 2.6&nbsp;million gigaton sheet. On 19 September 2014, for the first time since 1979, Antarctic sea ice extent exceeded 7.72&nbsp;million square miles (20&nbsp;million square kilometres), according to the [[National Snow and Ice Data Center]]. The [[ice extent]] stayed above this benchmark extent for several days. The average maximum extent between 1981 and 2010 was 7.23&nbsp;million square miles (18.72&nbsp;million square kilometres). The single-day maximum extent in 2014 was reached on 20 Sep, according to [[NSIDC]] data, when the sea ice covered  7.78&nbsp;million square miles (20.14&nbsp;million square kilometres). The 2014 five-day average maximum was reached on 22 Sep, when sea ice covered 7.76&nbsp;million square miles (20.11&nbsp;million square kilometres), according to [[NSIDC]].<ref>{{cite web |title=Antarctic Sea Ice Reaches New Record Maximum|date=8 April 2015|url=https://www.nasa.gov/content/goddard/antarctic-sea-ice-reaches-new-record-maximum|publisher=NASA Goddard Space Flight Center|access-date=10 May 2017}}</ref> This increase could be due to the reduction in the [[salinity]] of the [[Antarctic Ocean]] as a result of the previous melting of the ice sheet, by increasing the [[Freezing-point depression|freezing point]] of the seawater.

The current rate of decline of the ice caps has caused many investigations and discoveries on glacier dynamics and their influence on the world's climate. In the early 1950s, scientists and engineers from the US Army began drilling into polar ice caps for geological insight. These studies resulted in "nearly forty years of research experience and achievements in deep polar [[ice core]] drillings... and established the fundamental drilling technology for retrieving deep ice cores for climatologic archives."<ref>{{cite journal|last=Langway|first=Chester|title=The history of early polar ice cores, Cold Regions Science and Technology|date=April 2008|volume=52|issue=2|pages=101–117}}</ref> Polar ice caps have been used to track current climate patterns but also patterns over the past several thousands years from the traces of {{chem|CO<sub>2</sub>}} and {{chem|CH<sub>4</sub>}} found trapped in the ice. In the past decade, polar ice caps have shown their most rapid decline in size with no true sign of recovery.<ref>{{cite web|url=http://thewatchers.adorraeli.com/2011/03/10/polar-ice-is-melting-more-faster-than-predicted/|title=Polar ice is melting more faster than predicted|date=10 March 2011 |publisher=The Watchers|access-date=18 May 2015}}</ref> Josefino Comiso, a senior research scientist at NASA, found that the "rate of warming in the Arctic over the last 20 years is eight times the rate of warming over the last 100 years."<ref>{{cite web |last=Thompson |first=Elvia |title=Recent Warming of Arctic May Affect Worldwide Climate |url=http://www.nasa.gov/centers/goddard/news/topstory/2003/1023esuice.html |publisher=[[NASA]] |access-date=2 October 2012 |archive-date=26 April 2021 |archive-url=https://web.archive.org/web/20210426063622/http://www.nasa.gov/centers/goddard/news/topstory/2003/1023esuice.html |url-status=dead }}</ref> In September 2012, sea ice reached its smallest size ever. Journalist John Vidal stated that sea ice is "700,000 sq km below the previous minimum of 4.17m sq km set in 2007".<ref>{{cite news |last=Videl |first=John |title=Arctic Ice Shrinks 18% against Record, Sounding Climate Change Alarm Bells |url=https://www.theguardian.com/environment/2012/sep/19/arctic-ice-shrinks |work=[[The Guardian]] |location=London |access-date=3 October 2012 |date=19 September 2012}}</ref> In August 2013, Arctic sea ice extent averaged 6.09m km<sup>2</sup>, which represents 1.13&nbsp;million km<sup>2</sup> below the 1981–2010 average for that month.<ref>National Snow and Ice Data Center [http://nsidc.org/arcticseaicenews/2013/09/a-real-hole-near-the-pole/ A real hole near the pole], 4 September 2012</ref>