sciencenewsf o rkids.o rghttp://www.sciencenewsforkids.org/2013/09/ancient-mud-from-far-below-antarcticas-ice-promises-to-tell-a-riveting-tale-about-earths-ancient-climate/
Mud coating th is s cientis t’s finger was re tr ieved jus t hours ear l ie r from the bottom of Lake Whi l lans . Its water l ies a ha l f-m i leunder a b lanket o f s o l id ice in Antarctica . Ear l ie r th is year , s cientis ts fina l ly dr i l led in to the lake, whos e water has not s een
Whillans Ice St ream, Antarct ica — Reed Scherer and Ross Powell have studied mudfrom all over the world. It is different in each place. Mud from the Sulu Sea near Borneo is assmooth as cream cheese. Mud from Chesapeake Bay, in the mid-Atlantic United States,clings to your skin like peanut butter. Okefenokee Swamp mud, from Georgia, stinks with therotting goo of plants and animals that died long ago. You can tell a lot about a place byreading its mud. But sometimes that mud is hard to come by.
At 8 a.m. on Jan. 30, 2013, Scherer and Powell stood nervously outside in a cold wind. Thetwo men had picked a strange place to look for mud. In every direction, pristine white icestretched outas far as theeye couldsee. Thisremote spotin Antarcticawas just 600kilometers(375 miles)from theSouth Pole.
Antarctica’sice coversan areanearly twiceas large asthe lower 48U.S. states.Its depthwhereScherer andPowell werestanding wasequal to nineStatues ofLibertystacked ontop of eachother. There was not a speck of brown on the surface of the ice. But deep below lay the real Antarctica — a hiddencontinent of rock, water and mud. Far below their boots was Lake Whillans, a body of water no human has ever seen.
Scherer and Powell had traveled to the bottom of the world from Northern Illinois University in DeKalb. Scherer is amicropaleontologist, which means he studies the tiny fossils of things that lived long ago. Powell is a geologist whostudies the thick layers of mud and gravel that glaciers leave behind as they move. After years of waiting, they finallyhoped to extract samples of mud from the floor of this lake buried beneath the ice.
( top im age) Th is s ki -equ ipped Bas ler DC-3 p lane flew s om e people and equ ipm ent out to Lake Whi l lans . Th is s ubg lacia l lakel ies 1,000 ki lom eters in land from a bas e on the coas t o f Antarctica . Mos t Bas ler DC-3s were bu i l t in the 1940s . But even today,thes e o ld p lanes are s ti l l wide ly us ed in Antarctica . They can land and take o ff on s oft s now or rough ice where o ther p lanes
cannot. (bottom im age) Over 450,000 ki logram s (1 m i l l ion pounds ) o f dr i l l ing m ach inery, fue l and s cienti fi c gear was towedon the ground to the lake s i te on m as s ive m eta l s leds . Th is 1,000-ki lom eter (600 m i le) “ travers e” took two weeks . The s led
This wasone of themost remote, inhospitable sites that the two scientists had ever visited in search of mud. And there were no guaranteesof success. But before the day was over, Scherer and Powell would touch an ancient, distant world — and bear thebroad grins to prove it.
Oh, the ant icipat ion
Over the previous week, engineers had slowly, carefully drilled through the ice. Lots of ice. They had to create a hole800 meters (half a mile) deep to reach Lake Whillans. Scherer and Powell knew that the lake had a muddy bottombecause when the drill first came back up, they found tantaliz ing traces of mud smeared on it. Now, the two men hopedto grab enough of that mud to do some proper scientific studies. They lowered a contraption with three plastic pipesdown a metal cable. They hoped to jam those pipes into the lake bottom and pull up plugs of mud.
But all was not going according to plan. Twice the plastic pipes had gone down. Twice they surfaced empty. No oneknew why.
Engineers have as s em bled a m eta l p la tfo rm over the s pot where a ha l f-m i le -deep ho le was dr i l led down to Lake Whi l lans .Som e of the s cienti fi c equ ipm ent lowered in to the lake was s o heavy that i t had to be l i fted wi th a crane ( r igh t s ide o f photo) .
Undaunted,Scherer andPowell hadsent thepipes for thethird time onan hour- longdescentdown thenarrow holeto the lake.
Now thepipes werecoming upagain. Inanticipation,Scherer andPowellleaned overa metal rail,staring downthe hole. Thecablecrackled andpopped as itinched upand out ofthe hole.Flecks of ice splintered off the line as it coiled back onto a motorized spool.
“Ten meters… seven meters… five meters,” called out the spool operator. He was counting off the last bit of cablebefore the cores of mud were supposed to rise into view. “Do we have a visual yet?”
“No,” said Powell. He was anxious. Ice drilling is inexact. Lots of expensive scientific gear has been lost in holes,wedged forever in the ice.
Imagine reeling in a fishing line, hoping for a fish — but fearing the hook might simply have snagged a tin can or clumpof seaweed. That is how Scherer and Powell felt. A lot was at stake.
Hidden world
The dark world under Antarctica’s ice is one of the least- known places on Earth. Much of what is known comes,ironically, from high above. Airplanes have pointed their radar instruments down at the ice to survey the seeminglyendless fields of sparkling whiteness. Those fields are known as ice sheets.
Explainer
Antarctica, land of lakes
The radars bleep out radio waves. After rippling down through the ice, those waves bounce back up from the continentbeneath. Those echoing radio waves allow scientists to see through the ice. As the plane flies in a straight line, it mapsthe ups and downs of the subglacial landscape deep below. Those measurements have revealed unseen mountainranges and more than 200 lakes.
Scientists have also drilled through the ice here and there to sample, directly, what the radar has found. After a few hoursor days, those holes always squished shut again. But what the researchers retrieved before that happened has inspireddeep questions about how long the ice has been there — and what might happen if it vanished again.
It’s precisely these questions that have puzz led, and rattled, Scherer since he was 30 years old, back in 1987. That’swhen he first got his hands on several plastic bags of greenish-brown mud from Antarctica.
Scientists had accidentally stumbled onto that mud while drilling into an ice sheet. They had wanted to study the lowestlayers of the ice. But they drilled too far: When they pulled their drill up, it was caked in frozen mud.
The site was 200 kilometers (125 miles) from where Lake Whillans would later be found.
As a paleontologist, Scherer studies ancient fossils. In his case, they’re microscopic ones. After sifting the Antarctic mudto remove gritty sand, he smeared what was left onto a glass slide. Then he viewed it under a microscope. Squintingthrough the eyepiece, he saw something beautiful.
Dozens of curvy, crystal- clear shapes stared back at him. Some were covered in spikes. Others appeared dotted withholes, like the pattern atop a saltshaker. The images resembled lovely pieces of museum art. Yet Scherer recognizedthem as relics of life. These were the shells of diatoms — tiny sea creatures — made of silica. Silica is the clear mineralthat makes up glass.
To find diatom shells in mud below thick Antarctic ice had big implications. Diatoms are like plants: They need sunlightto photosynthesize and grow. So they could have grown only when this portion of West Antarctica was free of ice.Indeed, this region must have held a shallow sea.
Most shells in this mud sample were 10 million to 20 million years old. This came as no surprise. Scientists alreadyknew that throughout much of that time the world had been warmer and Antarctica’s ice sheet smaller. But as Schererlooked at mud from a second hole, he saw something that surprised him deeply.
A few of its diatoms were much younger. They seemed less than 600,000 years old. Some might be only 120,000 yearsold. They were species that weren’t around any earlier than that.
If true, that
Scherer ’s group re tr ieved the round, ar ts y-looking d ia tom ( top im age) from Antarctica rough ly 20 years ago. It da tes back tothe P le is tocene era , s om e tim e wi th in the las t m i l l ion years . The d ia tom in the b lack-and-whi te im age (bottom ) was re tr ievedth is year from Lake Whi l lans ; i t appears to have com e from the Miocene era , around 8 m i l l ion years ago. Cred i t: R. Scherer ,
Nor thern Il l ino is Un iv.
If true, thatwould beshocking. Itmeant thatmuch ofWestAntarctica’sglacial coverwas faryounger thananyone hadthought. Aswath of icelarger thanFrance mustbe muchlesspermanentthan glacialexperts hadassumed. Ifthe ice nowcovering thispart ofAntarcticamelted, itwould raiseglobal sealevels by upto fivemeters (16feet). FromLondon andNew York toMiami,Jakarta andShanghai,many of theworld’scoastal citieswould sufferdevastatingflooding. AndScherer’sdiatoms nowhinted thatsuch acatastrophicmelting ofthe WestAntarctic IceSheet couldbe far morelikely thanclimatescientists had thought.
The s ed im ent “corer ” des cends toward Lake Whi l lans , th rough a ho le dr i l led in the ice . The ho le is 800 m eters (ha l f a m i le )deep and no wider than a p iz z a. The equ ipm ent is be ing viewed through the p la tform (b lur red la ttice-work in th is im age) on
Scherer published his findings in 1998. And some scientists found them hard to swallow.
Experts came up with other possible explanations for the young diatoms. Maybe winds had blown them onto the top ofthe ice, after which they melted down to where Scherer found them.
Living creature
To probe all of this further, Scherer has wanted to get more mud. Those samples could tell him the last time the WestAntarctic Ice Sheet collapsed, meaning that it had suddenly vanished.
“That’s something I’ve been trying to address through my whole career,” he notes. “Scientists had known it hadcollapsed, but not precisely when that was.”
So Scherer was thrilled at the chance to grab another precious sample of mud earlier this year.
The drill punched into Lake Whillans on January 27. At 11 p.m., 30 scientists and drillers gathered in a wooden hut tomake final plans. Slawek Tulaczyk stood and spoke first. The group’s ice expert, he comes from the University ofCalifornia, Santa Cruz . He noted that the hole, no wider than a large pizza, would gradually freeze shut from the intensecold.
Another problem might also occur, he notes. Most people see ice as solid and hard, like glass. But when the ice ismore than a few hundred meters thick, as it was here, it behaves in strange ways. The immense weight pressing downfrom above causes the ice to squish and ooze like Silly Putty. As a result, the walls of the hole might actually squeezeshut.
“Thisborehole isa livingcreature,”Tulaczyktold thegroup. “It’schangingover time.” And sobegan arace againstthe clock topull up asmanysamples oflake waterand mud aspossiblebefore thehole lockedshut.
First, a teamof biologistsworkednonstop for20 hoursbringing upbottles of water. Fine mineral dust rendered this liquid the color of honey. Within hours, the scientists had samples of thefluid under a microscope. And they found living cells. Each teaspoon of water contained about a half-million of them.
By a narrow margin, those single-celled microbes were the first direct evidence of life in a subglacial lake in Antarctica.(See “Piercing a buried polar lake” to learn more.) A few weeks later, in March, a Russian team would report finding
As Ros s Powel l (on le ft) looks on, Reed Scherer (m uddy hands ) takes ho ld o f the corer . It has jus t em erged from LakeWhi l lans fu l l o f m ud. Scherer and Powel l wear cl im bing harnes s es that are connected to the m eta l fram e above — jus t in
microbes in samples of frozen water from Antarctica’s buried Lake Vostok.
After the biologists at Lake Whillans pulled up their samples of lake water, Scherer and Powell had their turn to probe formud. On their second try, the equipment bumped into something 760 meters down the hole. It stopped there, only a fewagoniz ing meters short of the lake.
So crews lowered the drill back down the hole to widen it. This ate up 18 hours of precious time. The Antarctic summerwas drawing to a close. The team would have to begin leaving within three days — whether Scherer and Powell got theirmud or not. So when the mud grabber went down the hole for a third time on the morning of January 30, no one knewhow many more tries would be possible.
Frozen goo
At 8:24 a.m., the spool operator counted off the last few meters of cable coming up. “Three and a half meters… onemeter.”
People gathered around. Powell and Scherer leaned over the hole. Then something dark came into view.
“We have sediment!” shouted Powell. The onlookers cheered. The thing that emerged from the hole resembled amudcicle: The dripping glops of brown goo had frozen solid during the journey back up the hole.
As scientistslifted theplastic pipesand carriedthem into alaboratory,some of themudsplatteredaround.Peoplerubbed itbetweentheir fingers.It was gritty,full of sandthat glaciershad mixed inas theybulldozedover thehidden faceof Antarctica.
Shat teredglass
Scherer’sjob lookingat diatoms from Lake Whillans will not be easy. He realized this as he looked at those first, limited samples of lake mudfrom the drill head under a microscope. Sure enough, he saw diatom shells. But they were not the perfect museum artthat he had seen in samples from other locations. Instead, imagine that the beautiful diatom shells had been hit by atrain and dragged on and on. That is what glaciers do. The dragging had shattered every microscopic diatom shell.
Scherer nudged the slide around, looking for a shell that wasn’t so badly crushed. “I’m a glutton for punishment,” hesaid, “working on this nasty stuff.”
A person like Scherer who studies diatoms must learn to recognize hundreds of different types. Different species live in
different environments. So those in a dab of mud can give clues to the climate in which they had once lived.
Explainer
Ice sheets and glaciers
At last, Scherer found a shell that he recognized. Its flat disk looked like a piece from a checkers game, but dotted withholes. Members of its species are still found elsewhere, he noted. “They’re pretty common in Norway today.” The onedredged up from Lake Whillans and now under his microscope was not alive, however. When it had lived, WestAntarctica was probably about as warm as the coastal waters off Norway are today. Lake Whillans would have had noice covering it, back then, except for perhaps a topcoat layer just one meter (one yard) or so thick during winter.
Rare youngsters
Within days of extracting the mud from Lake Whillans, the scientists had packed up the samples and sent them along tolaboratories in the United States. Back in northern Illinois, Scherer’s team is now hard at work analyz ing the mud. Thescientists will have to peer at thousands of diatom shells before a clear picture of past environments begins to emerge.Most of the shells will be more than 10 million years old. But the scientists will keep scouting for signs of youngsters —diatoms closer to 500,000 years old.
Scherer is working with great care. He has bought a new set of laboratory beakers and flasks to hold the precious bits ofmud. “I don’t use old glassware for this stuff since the concentration of diatoms is so low,” he says. A few straymicroscopic diatoms from an older project might taint his results, and “I just want to make sure there’s no contamination,”he explains.
Retrieving this mud cost “many, many millions of dollars,” Scherer told Science News for Kids, “making it worth more thangold — a lot more.” But its greatest value lies in the story it promises to unveil.
Its diatoms will shed more light on when West Antarctica was last ice- free. This, in turn, could hint at how stable theregion’s ice sheet has been over time. Knowing that is especially important now that rising global temperatures aremelting glaciers and other major reservoirs of ice.
The dr i l l ing cam p at Lake Whi l lans covered two acres . But i t s eem s s m al l am id Antarctica ’s vas t ice s heet. Peop le working a tthe cam p s tayed in 28 s m al l ye l low tents la id out in rows (author Douglas Fox s lept in the s econd tent from the r igh t in the
The worldunderAntarctica’sice still holdsmanysecrets. Twodecadesago, no onerealized thata complexnetwork ofrivers —dotted withlakes —crisscrossedthiscontinent.Now thatLakeWhillans hasfinally beenbreached, itsmud couldprovidemany cluestoAntarctica’slong andprivate life.
Power Words
Antarct ica A continent mostly covered in ice surrounding the South Pole. Ice sheets cover about 98 percent of thissouthernmost continent.
cell The smallest, microscopic unit of life. It consists of watery fluid surrounded by a membrane or wall.
core A cylinder bored or drilled out of something, such as mud, rock or ice. In geology, cores allow scientists to samplelayers going back in time. A core of mud can be obtained by driving a hollow pipe down into the material; when the pipeis lifted, the mud stays inside.
diatoms Tiny, ocean-dwelling organisms similar to algae that are made of no more than a few cells. Diatoms haveshells made of silica, a compound also used in glass. They live like plants, using sunlight to turn carbon dioxide intosugars.
echo The return of a wave after it has bounced off a surface. The echo of sound waves can be heard. Radio waves toocan bounce off surfaces that reflect them. That principle is used in radar (see below).
fossil A physical remnant of something that lived long ago. Examples of fossils include dinosaur bones, theimpressions of seashells in rocks and the preserved shells of ancient diatoms.
glacier A slow-moving river of ice hundreds or thousands of meters deep. Glaciers are found in mountain valleys andalso form as parts of ice sheets.
ice sheet The broad blanket of ice, most of it kilometers deep, that covers most of Antarctica. An ice sheet alsoblankets most of Greenland.
microbe Living things too small to see with the unaided eye. These include bacteria, some fungi and many otherorganisms such as amoebas.
microscope A scientific instrument used for looking at things, like diatoms or single-celled microbes, too small to bevisible to the unaided eye.
photosynthesis The use of sunlight by plants, diatoms and some other organisms as an energy source to convertcarbon dioxide into sugars that serve as food.
radar (radio detection and ranging) A technique to throw off radio waves and then detect the echo of any waves that arereflected back. Radar can be used to detect moving objects, such as airplanes. It can also be used to map the shapeof land — even if covered by ice.
radio waves A type of electromagnetic radiation. It is similar to visible light, but at a lower frequency. It is used totransmit radio and television signals; it is also used in radar.
sea level The overall level of the ocean over the entire globe when all tides and other short- term changes areaveraged out.
silica A compound, composed of the elements silicon and oxygen, that makes up glass and the glasslike shells ofdiatoms.
subglacial Underneath a glacier or ice sheet. Subglacial lakes, for instance, lay hundreds to thousands of metersbeneath Antarctica’s ice sheet.
