ISSUE #27 II MARCH-APRIL 2007 DE LVING IN TO THE PAST TO PRED ICT THE FUT URE AN ARCT IC RESE ARC HER YIE LDS A TREAS URE TROVE OF CLIMATE CHANGE INFORMATION FROM THE BOTTOM OF LAKES. By Ryan Stuart

PROJECT When Arctic researcher Marianne Douglas [1] looks at a lake, she does n't just think abo ut taking a dip or getting a drink. She wo nde rs what clues to the past are hidden in its wa tery depths.

Specifically, she wonders about diatom s [2]. These min ute organisms ca n be found in almost eve ry pond and lake on earth, and when they die, th ey lea ve behi nd glas s ce ll wall s th at pile up in layers at th e bottom of lakes. Similar to rings in a tree trun k, these layers ho ld a lot of information abo ut past climate.

"They're like little jewels under the microscope," Dougla s says. "Each s pec ies has its own ornamentation and occupies its own s pecific niche. As env ironmental conditions cha nged, so did the s pecies. We take core s amples of the lakebeds, a nd as you go down in th e sections, you're going bac k in time. Some of the changes a re abso lute ly dra matic-huge, huge changes."

Doug las's pass ion is finding and unravell ing thos e changes us ing a s ci­ en ce called pa leo limnology [3]. What looks like Arctic pond s cum to the average person is actually a clear timeli ne of ecological cha nge un der Douglas's train ed eye. She us es 20 years of paleolimnological res earch to s how how the Arctic's clima te is changing, to fill in the holes in Arctic climate dat a, and to tes t forward-looking clima te models.

Douglas first looked to diatoms as a vehicle to the past in 1986 as a grad s tude nt worki ng with Jo hn Smol [4], a paleolimnologist at Queen 's University. Smol s ent her to Cape Herschel on Elles me re Is la nd, the most nort herly isl and in the Arctic Archi pelago, to collec t samples [5] from s ma ll lakes an d pond s. Bac k in th e lab that fall, Douglas started exam ining th e sediment samples a nd was ast ounde d at what s he found. She had expected th e types of dia toms in the sediment to change s lowly over time as the climate gradually warmed from th e Ice Age to present day. Instead, the s amples s howed that for 4,000 years, on ly three or four speci es of diatoms dominated. Then, surprisingly, the dating samples [6] confirmed that after abo ut 1850, diat om divers ity jumped to more than 100 additional s pecies. , , "It would be like going to sleep having only three or four neighbours and the n waking up in a new s ubdivision," Douglas s ays. "In biolog ical terms, it wa s a dr asti c cha nge."

Using ice core data [7], Douglas concluded that the pos t-1 850 changes were caused by decreased volcanic activi ty and increased solar acti v­ ity. This, along with possible early effects of human-infl uenced warming, caused the temperature to ris e. That meant the Arctic lake ice me lte d earlier in the year th an usual, providing a longe r growing season for aquatic mos ses and the like . That in turn cre ate d new nich es for differ­ e nt types of diatoms to develop . 'What we're seeing is th e tippi ng point," s he sa ys . "The ecological th reshold was reached," Before 1850, the liv­ ing conditions in th e lakes we re s o extre me that on ly a few s pec ies could thr ive. Around 1850, the environme nta l conditions in the lake change d and, suddenly, dozen s of species cou ld thrive.

Further study revealed another marked increase in life in the 1920s, which coincided with increased carbon dioxide readings in ice cores ca used by th e burning of fossi l fue ls . It prom pted Douglas , in 1994, to publis h one of the ea rly sc ientific pape rs s howing th e effec ts of globa l warming in th e Arctic.

"Her finding s were very controvers ia l at the time," Smol says. Not so today. Most scientists now believe in globa l warm ing- in fact, physicists and climatologist s us e Doug las's findings to predict how the weather will change in the future. Predictions are made with global clim at e model s [8] generated by powerful computers tha