The Earth Institute at Columbia University, June 8, 2005--The end of the recurring, 100,000-year glacial cycles is one of the most prominent and readily identifiable features in records of the Earth's recent climate history. Yet one of the most puzzling questions in climate science has been why different parts of the world, most notably Greenland, appear to have warmed at different times and at different rates after the end of the last Ice Age.
Aerial view of glacial moraine (parallel lines of hills) surrounding Lake Pukaki in southern New Zealand sampled by the researchers that mark the advance of the Tasman glacier (upper left). Credit: George Denton
However, a new study appearing in the upcoming issue of the journal Science suggests that, except for regions of the North Atlantic, most of the Earth did, in fact, begin warming at the same time roughly 17,500 years ago. In addition, scientists suggest that ice core records from Greenland, which show that average temperatures there did not warm appreciably until about 15,000 years ago, may have remained in a hyper-cold state largely as a result of events triggered by warming elsewhere.
The research, led by Joerg Schaefer from the Lamont-Doherty Earth Observatory, a member of The Earth Institute at Columbia University, and George Denton at the University of Maine, relied on a method known as cosmogenic or surface-exposure dating, which enabled the scientists to determine how long rock surfaces have been exposed since the glaciers retreated. As cosmic rays penetrating the Earth's atmosphere strike the scoured rock, they form an isotope of the element beryllium, 10Be, at a known rate. By measuring the minute amounts of 10Be in rock samples from glacial moraines in California and New Zealand and comparing these data to previously published results from Wyoming, Oregon, Montana Argentina, Australia and Switzerland, Schaefer and his colleagues were able to narrow down when glaciers around the world began to retreat. They found that almost everywhere they looked the glaciers began to pull back approximately 17,500 years ago. Additional studies from tropical South America southern Tibet have also produced similar results.
"It's amazing everything fits so well and that every moraine record of the last termination seems to match with rising temperature in the Antarctic and CO2 in the atmosphere," said Schaefer, a Doherty Associate Research Scientist. "It's especially surprising because Antarctica was classically thought to be too remote and climatically isolated to respond in a synchronous manner with the rest of the planet." The only place that does not fit the observed warming pattern is Greenland, which did not begin to emerge from the last Ice Age until roughly 15,000 years ago. The authors believe that this anomaly may be because the North Atlantic experienced continued, hyper-cold winters during the intervening 2,500 years that prevented the region from warming on average.
Glaciers, they write, are highly sensitive to summer temperatures. Instead of responding to the rise in global summer temperatures that occurred around 17,500 years ago, however, Greenland may have experienced a continued ice age climate caused by massive armadas of icebergs from the melting continental ice sheets on North America and Northern Europe spreading across the North Atlantic. The freshwater from the melting icebergs likely caused an ocean current known as the meridonal overturning circulation, which transports heat northward from the equator, to almost cease and prevent Greenland and the North Atlantic from warming for millennia after the rest of the planet had begun to do so.
"The spreading sea ice would have also brought the circum-polar winds farther south," said Schaefer. "This would have interfered with temperature and precipitation patterns in the northern mid-latitudes and put the North Atlantic in the deep freeze for 2,500 years."
Ken Kostel | EurekAlert!
Modeling magma to find copper
13.01.2017 | Université de Genève
What makes erionite carcinogenic?
13.01.2017 | Friedrich-Schiller-Universität Jena
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
UMD, NOAA collaboration demonstrates suitability of in-orbit datasets for weather satellite calibration
"Traffic and weather, together on the hour!" blasts your local radio station, while your smartphone knows the weather halfway across the world. A network of...
Fiber-reinforced plastics (FRP) are frequently used in the aeronautic and automobile industry. However, the repair of workpieces made of these composite materials is often less profitable than exchanging the part. In order to increase the lifetime of FRP parts and to make them more eco-efficient, the Laser Zentrum Hannover e.V. (LZH) and the Apodius GmbH want to combine a new measuring device for fiber layer orientation with an innovative laser-based repair process.
Defects in FRP pieces may be production or operation-related. Whether or not repair is cost-effective depends on the geometry of the defective area, the tools...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
16.01.2017 | Power and Electrical Engineering
16.01.2017 | Information Technology
16.01.2017 | Power and Electrical Engineering