AUTHORS Making the Paper: Joanne Johnson

Exposed boulders on the harsh terrain of west Antarctica harbour a warning that the region’s glaciers could collapse.

Joanne Johnson’s fi rst chance to explore of bedrock outcrops dotted with lumps the fastest-melting glaciers of the West of pinkish granite. She planned landing Antarctic came unexpectedly, sites in advance, but “When you get there, nearly two years ahead of schedule. But it you look at it and you think, it’s too steep was also overdue. or too icy, we can’t land here — then Satellite data and ground-based you have to start making decisions,” measurements had raised alarms that she recalls. fast-fl owing glaciers near Pine Island Bay Having made it to the ground, they could disintegrate completely, raising fought winds that limited their ability to global sea levels by a metre. Yet Johnson, collect data, and sometimes even to stand whose work has now validated concerns upright. One area reached with diffi culty that the glaciers there are melting rapidly, had to be abandoned suddenly when was the fi rst to set foot on the region’s the wind changed and ice began to close rocky bluff s in four decades. in behind the waiting ship. Meanwhile, Th e trip represented not only a the metre-wide boulders whose surfaces challenge for Johnson, a geologist with Johnson expected to sample were nowhere the British Antarctic Survey (BAS), to be found. Instead, she scooped up six but a change in her scientifi c direction. football-sized substitutes. “Here,” says Previously, while working on ancient Johnson, “you grab what you can.” volcanoes, she had set out by foot from Joanne Johnson in the Antarctic. Th e recently published analyses fi eld camps to collect rocks from the ( 36, 223–226; 2008) show that relatively placid northern Antarctic the glaciers have been thinning for at least Peninsula. But now she found herself in when — and how quickly — the glaciers 14.5 thousand years at approximately search of large granite boulders in one of thinned. Lacking that historic perspective, 2.3–3.8 centimetres per year, on average. the continent’s most remote and punishing scientists couldn’t be sure that the melting Contrasted with the 1.6-metre-per-year regions. Far from any research base, on seen today is much diff erent from the ice detected by satellite from terrain scoured by winds and guarded by sheets’ past behaviour. 1992 to 1996, Johnson’s results support capriciously shift ing sea ice, Johnson was Johnson’s demanding journey began fears that global warming is pushing looking for chemical clues in rocks left when she joined a German icebreaker the glaciers toward collapse. Th e sparse behind by glaciers that had melted over bound for Pine Island Bay in 2006, ahead initial measurements will be fi lled in the past several millennia. of her planned 2007–2008 fi eld trip with by forthcoming data, including some Th e crucial clues were beryllium-10 BAS. Sailing aboard the RV Polarstern, from Johnson’s colleagues, who have just and certain other isotopes, formed in she was, among 100 scientists and crew, returned to fi nd the sea ice much tamer. the granite when boulder-bearing glacial one of four who spoke no German. It was Aft er fi ve years of virtually impassable currents shrank back from mountaintops easier to circumvent the language barrier, sea ice in Pine Island Bay, says Johnson, and left the rocks high and dry — and however, than the sea ice. Once the ship “Ironically, at the moment it’s quite open.” exposed to cosmic rays from space. managed to manoeuvre close to the As the isotopes accumulate over time glaciers, Johnson and her fi eld assistant Anna Barnett is assistant editor and copy in ice-free rock, they provide a measure of would strike out by helicopter in search editor of Nature Reports .

48 nature reports climate change | VOL 2 | APRIL 2008 | www.nature.com/reports/climatechange