| 
  • If you are citizen of an European Union member nation, you may not use this service unless you are at least 16 years old.

  • Social distancing? Try a better way to work remotely on your online files. Dokkio, a new product from PBworks, can help your team find, organize, and collaborate on your Drive, Gmail, Dropbox, Box, and Slack files. Sign up for free.

View
 

Arctic Ice Least for 3000 years

Page history last edited by Malcolm 9 years, 12 months ago

Arctic ice at multi-millennium low: researchers

June 3, 2010
Courtesy of Ohio State University
and World Science staff

Less ice co­vers the Arc­tic to­day than at any time in the past few thou­sand years. So says an in­terna­t­ional group of re­search­ers that has com­piled what they call the first com­pre­hen­sive his­to­ry of Arc­tic ice.

For dec­ades, sci­en­tists have strived to col­lect sed­i­ments from the difficult-to-access Arc­tic Ocean floor, to find out what the Arc­tic was like in the past. Their most re­cent goal: to br­ing a long-term per­spec­tive to the ice loss we see to­day.

Arc­tic sea ice ex­tent in Au­gust 2009 – the ar­ea of the Arc­tic Ocean cov­ered by float­ing ice – as meas­ured by NA­SA satel­lites. It was the third low­est ex­tent since sat­el­lite mea­sure­ments were first made in 1979. (Cour­te­sy NA­SA)
Now, in an up­com­ing is­sue of the jour­nal Quar­ternary Sci­ence Re­views, a team led by Ohio State Uni­vers­ity has re-ex­am­ined the da­ta from nearly 300 past and on­go­ing stud­ies and com­bined them to form a big-pic­ture view of the pole's cli­mate his­to­ry.

"The ice loss that we see to­day—the ice loss that started in the early 20th Cen­tu­ry and sped up dur­ing the last 30 years—ap­pears to be un­matched over at least the last few thou­sand years," said Le­o­nid Polyak, a re­search sci­ent­ist at Byrd Po­lar Re­search Cen­ter at Ohio State Uni­vers­ity. Polyak is lead au­thor of the pa­per and a pre­ced­ing re­port that he and his coau­thors pre­pared for the U.S. Cli­mate Change Sci­ence Pro­gram.

Satel­lites can pro­vide de­tailed meas­ures of how much ice is co­vering the pole right now, but sed­i­ment co­res are like fos­sils of the ocean's his­to­ry, he ex­plained. A sed­i­ment co­re is a pole-shaped sam­ple of sed­i­ments ob­tained by push­ing a hol­low tube in­to the sed­i­ment and then pulling it out. This al­lows sci­en­tists to ex­am­ine many lay­ers of sed­i­ment cor­re­spond­ing to dif­fer­ent time pe­ri­ods.

"Sed­i­ment co­res are es­sen­tially a rec­ord of sed­i­ments that set­tled at the sea floor, lay­er by lay­er, and they rec­ord the con­di­tions of the ocean sys­tem dur­ing the time they set­tled," said Polyak. "When we look care­fully at var­i­ous chem­i­cal and bi­o­log­i­cal com­po­nents of the sed­i­ment, and how the sed­i­ment is dis­tribut­ed—then, with cer­tain skills and luck, we can re­con­struct the con­di­tions at the time the sed­i­ment was de­posit­ed."

For ex­am­ple, sci­en­tists can search for a bio­chem­i­cal mark­er that is tied to cer­tain spe­cies of al­gae that live only in ice. If that mark­er is in the sed­i­ment, then that loca­t­ion was likely co­vered in ice at the time. Sci­en­tists call such mark­ers "prox­ies" for the thing they ac­tu­ally want to mea­sure—in this case, the ge­o­graph­ic ex­tent of the ice in the past.

While know­ing the loss of sur­face ar­ea of the ice is im­por­tant, Polyak said that this work can't yet re­veal an even more im­por­tant fact: how the to­tal vol­ume of ice—thick­ness as well as sur­face ar­e­a—has changed over time. "Un­derneath the sur­face, the ice can be thick or thin. The new­est sat­el­lite tech­niques and field ob­serva­t­ions al­low us to see that the vol­ume of ice is shrink­ing much faster than its ar­ea to­day. The pic­ture is very trou­bling. We are los­ing ice very fast," he said.

* * *

__._,_.___

Comments (0)

You don't have permission to comment on this page.