Editing Ice core (section)

=== Radionuclides ===
[[File:Upper Fremont glacier ice cl36.gif|thumb|[[chlorine|<sup>36</sup>Cl]] from 1960s nuclear testing in US glacier ice.|alt=Graph showing abundance of <sup>36</sup>Cl against snow depth, showing a spike at the time of above-ground nuclear testing|300x300px]]

[[Galactic cosmic rays]] produce {{chem|10|Be}} in the atmosphere at a rate that depends on the solar magnetic field.  The strength of the field is related to the intensity of [[solar radiation]], so the level of {{chem|10|Be}} in the atmosphere is a [[Proxy (climate)|proxy]] for climate.  [[Accelerator mass spectrometry]] can detect the low levels of {{chem|10|Be}} in ice cores, about 10,000 atoms in a gram of ice, and these can be used to provide long-term records of solar activity.<ref>{{Cite journal|last=Pedro|first=J.B.|year=2011|title=High-resolution records of the beryllium-10 solar activity proxy in ice from Law Dome, East Antarctica: measurement, reproducibility and principal trends|journal=Climate of the Past|volume=7|issue=3|pages=707–708|doi=10.5194/cp-7-707-2011|bibcode=2011CliPa...7..707P|doi-access=free}}</ref> [[Tritium radioluminescence|Tritium]] ({{chem|3|H}}), created by nuclear weapons testing in the 1950s and 1960s, has been identified in ice cores,<ref>{{cite journal|last1=Wagenhach|first1=D.|last2=Graf|first2=W.|last3=Minikin|first3=A.|last4=Trefzer|first4=U.|last5=Kipfstuhl|first5=J.|last6=Oerter|first6=H.|last7=Blindow|first7=N.|title=Reconnaissance of chemical and isotopic firn properties on top of Berkner Island, Antarctica|journal=Annals of Glaciology|date=20 January 2017|volume=20|pages=307–312|doi=10.3189/172756494794587401|doi-access=free}}</ref> and both [[Chlorine-36|<sup>36</sup>Cl]] and {{Chem|link=Plutonium-239|239|Pu}} have been found in ice cores in Antarctica and Greenland.<ref>{{cite journal|last1=Arienzo|first1=M. M.|last2=McConnell|first2=J. R.|last3=Chellman|first3=N.|last4=Criscitiello|first4=A. S.|last5=Curran|first5=M.|last6=Fritzsche|first6=D.|last7=Kipfstuhl|first7=S.|last8=Mulvaney|first8=R.|last9=Nolan|first9=M.|last10=Opel|first10=T.|last11=Sigl|first11=M.|last12=Steffensen|first12=J.P.|title=A Method for Continuous Pu Determinations in Arctic and Antarctic Ice Cores|journal=Environmental Science & Technology|date=5 July 2016|volume=50|issue=13|pages=7066–7073|doi=10.1021/acs.est.6b01108|pmid=27244483|bibcode=2016EnST...50.7066A|s2cid=206558530 |url=http://nora.nerc.ac.uk/id/eprint/513803/7/Arienzo_et_al_NWT_May2016_V1.pdf}}</ref><ref>Delmas et al. (2004), pp. 494–496.</ref><ref>{{Cite web|url=http://wwwbrr.cr.usgs.gov/projects/SW_corrosion/icecore/futurework.shtml|title=Future Work|date=14 January 2005|publisher=US Geological Survey Central Region Research|archive-url=https://web.archive.org/web/20050913192339/http://wwwbrr.cr.usgs.gov/projects/SW_corrosion/icecore/futurework.shtml|archive-date=13 September 2005}}</ref> Chlorine-36, which has a half-life of 301,000 years, has been used to date cores, as have krypton ({{Chem|link=krypton-85|85|Kr}}, with a half-life of 11 years), lead ({{Chem|link=lead-210|210|Pb}}, 22 years), and silicon ({{Chem|link=silicon-32|32|Si}}, 172 years).<ref name="Legrand-1997-2" />