(NSF press release, 4 May 2012) -- Changes in the speed that ice travels in more than 200 outlet glaciers indicates that Greenland's contribution to rising sea level in the 21st century could be significantly less than the upper limits some scientists thought possible. The finding comes from a paper funded by the National Science Foundation (NSF) and NASA and published in today's journal Science. While the study indicates that a melting Greenland's contributions to rising sea levels could be less than expected, researchers concede that more work needs to be done before any definitive trend can be identified. Studies like this one are designed to examine more closely and in greater detail what is actually happening with the ice sheets, often using newer and more precise tools and thereby better defining the parameters that scientists use to make predictions, such as the upper limits of sea-level rise.

"This study provides more evidence that the rate at which these glaciers can dump ice into the ocean is indeed limited," said Ian Howat, assistant professor of Earth sciences and member of the Byrd Polar Research Center at Ohio State University, a co-author on the paper. "What remains to be seen is how long the acceleration will continue--but it appears that our worst-case scenarios aren't likely." The fate of the Earth's ice sheets and their potential contributions to sea-level rise as the globe warms are among the major scientific uncertainties cited in the Fourth Assessment of the Intergovernmental Panel on Climate Change (IPCC). This is in part because the Greenland and Antarctic ice sheets have historically been, and in large measure continue to be, relatively sparsely monitored, as compared to other parts of the globe. The faster the glaciers move, the more ice and melt water they release into the ocean. ...

"This study is a great example of the power of high-resolution data sets in both space and time, and the importance of looking carefully at as much data as possible in helping make the best predictions we can of future changes", said Henrietta Edmonds, program director for Arctic Natural Sciences in NSF's Office of Polar Programs. The scientists saw no clear indication in the new research that the glaciers will stop gaining speed during the rest of the century, and so by 2100 they could reach or exceed the scenario in which they contribute four inches to sea level rise.

Tagged: Arctic, News, Polar research: Reports and findings

(American Association for the Advancement of Science press release via EurekAlert!, 26 April 2012) -- An analysis of 5,000-year-old DNA taken from the Stone Age remains of four humans excavated in Sweden is helping researchers understand how agriculture spread throughout Europe long ago. According to Pontus Skoglund from Uppsala University in Sweden and colleagues, the practice of farming appears to have moved with migrants from southern to northern Europe. Agricultural know-how wasn't the only thing that early European farmers introduced to the region. Based on their genetic data, Skoglund and the researchers say that Europe's first farmers eventually mixed their genes with the hunter-gatherers who lived there—a relationship that set the stage for today's modern European genome.

"We analyzed genetic data from two different cultures—one of hunter-gatherers and one of farmers—that existed around the same time, less than 400 kilometers (249 miles) away from each other," said Skoglund. "After comparing our data to modern human populations in Europe, we found that the Stone Age hunter-gatherers were outside the genetic variation of modern populations but most similar to Finnish individuals, and that the farmer we analyzed closely matched Mediterranean populations." These findings likely have something to do with the expansion of farming across Europe, according to the researchers. "When you put these findings in archaeological context, a picture begins to emerge of Stone Age farmers migrating from south to north across Europe," said Skoglund. "And the result of this migration, 5,000 years later, looks like a mixture of these two groups in the modern population." The researchers report their data in the 27 April issue of the journal Science, which is published by AAAS, the nonprofit international science society.

Most experts agree that the agricultural way of life originated about 11,000 years ago in the Near East before it reached the European continent some 5,000 years later. But this new study should help scientists understand the impact of that agricultural revolution on human diversity. Skoglund and his colleagues performed their analysis with the ancient remains of three hunter-gatherers who were associated with the Pitted Ware Culture and excavated from the island of Gotland, Sweden, along with those of a farmer, who was associated with the Funnel Beaker Culture and excavated from Gökhem parish, Sweden. "We know that the hunter-gatherer remains were buried in flat-bed grave sites, in stark contrast to the megalithic sites that the farmers built," said Mattias Jakobsson, a senior author of the Science report, also from Uppsala University. "The farmer we analyzed was buried under such a megalith, and that's just one difference that helps distinguish the two cultures."

Ancient hunter-gatherers had a distinct genetic signature that was similar to that of today's northern Europeans, while the farmer's genetic signature closely resembles that of southern Europeans, according to the researchers. Interestingly, these ancient genomes don't share many similarities with modern-day Swedes, despite their discovery and excavations in Sweden. "The fact that the hunter-gatherers are most similar to Finns, Orcadians and other extreme-northern populations suggests that they were indeed the last major part of the Mesolithic meta-population that populated large parts of Europe before the early farmers appeared," said Anders Götherström of Uppsala University, who is another senior author of the Science report. "And the fact that the farmer is most similar to southeastern Europeans makes sense too, as that is from where the spread of agriculture north and eastward started." "The results suggest that agriculture spread across Europe in concert with a migration of people," added Skoglund. "If farming had spread solely as a cultural process, we would not expect to see a farmer in the north with such genetic affinity to southern populations."

Tagged: History, News, Polar research: Reports and findings