south-polar ice rink sheets are still free a radioactive element as a outcome of nuclear weapons tests conducted by the US 70 eld ago , according to new enquiry write in theJournal of Geophysical Research : Atmospheres .
Chlorine-36is a naturally hap radioactive isotope that can shape when argon natural gas reacts with cosmic beam in the atmosphere . It can also form during atomic explosion over the ocean when neutrons react with atomic number 17 found in saltwater , which can disappear to the stratosphere , travel around the world , and ultimately become deposited on Antarctic water ice and snowfall where it can become permanently stored .
“ There is no more nuclear chlorine-36 in the global atmosphere . That is … why we should observe born chlorine-36 levels everywhere , ” said sketch source and geoscientist Mélanie Baroni in astatement .
The US conducted multiplenuclear weapon testsin the Pacific Ocean in the fifties and sixties . Inless than 20 years , a total of 19 in operation test serial were guide , resulting in more than230 detonations . Similar finding of chlorine-36 have been found in ice core samples from a US glacier locate in theWind River Mountain Range of Wyoming .
To square off how chlorine-36 behaves over time , especially in area with varying levels of snowfall , researchers took ice core samples dated between 1949 and 2007 from a Baron Snow of Leicester pit atVostok , a Russian research station in East Antarctica that get very little snow . They then compare it against sample from 1910 to 1980 taken from Talos Dome , a part located 1,400 kilometers ( 870 miles ) away that receive a lot of nose candy every twelvemonth .
Ice from Talos Dome was shown to decrease over fourth dimension and only keep about four time the point of natural chlorine-36 in 1980 . Vostok , on the other hand , testify very gamey levels – the top snow was 10 times the expected horizontal surface of naturally occurring chlorine-36 suggesting that C. P. Snow here is still releasing radioactive isotope from marine nuclear exam and that chlorine-36 is more roving than previously anticipate , moving upwardly from the depths .
The authors admonish that “ the aura of Vostok remain polluted by anthropogenic chlorine today . This pollution lead from gaseous mobility at low accumulation site and implies re?emission of chlorine-36 from the snowpack that is not observed at Talos Dome . ”
Researchers hope to next practice for a 1.5 - million - yr - old ice essence to better understand how Vostok releases chlorine-36 and to assist inform how it builds up in snowpack over time , informing how we date stamp ancient ice and infer Earth ’s climate .
