"Long before it's in the papers"
January 27, 2015

RETURN TO THE WORLD SCIENCE HOME PAGE


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.


* * *

Send us a comment on this story, or send it to a friend









 

Sign up for
e-newsletter
   
 
subscribe
 
cancel

On Home Page         

LATEST

  • St­ar found to have lit­tle plan­ets over twice as old as our own

  • “Kind­ness curricu­lum” may bo­ost suc­cess in pre­schoolers

EXCLUSIVES

  • Smart­er mice with a “hum­anized” gene?

  • Was black­mail essen­tial for marr­iage to evolve?

  • Plu­to has even cold­er “twin” of sim­ilar size, studies find

  • Could simple an­ger have taught people to coop­erate?

MORE NEWS

  • F­rog said to de­scribe its home through song

  • Even r­ats will lend a help­ing paw: study

  • D­rug may undo aging-assoc­iated brain changes in ani­mals

Less ice covers the Arctic today than at any time in the past few thousand years. So said an international group of researchers, who have 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. 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 samples 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.