The vast majority of the world's glaciers are retreating as the planet gets warmer. But a few, including glaciers south of the equator in South America and New Zealand, are inching forward.
A paper in this week's issue of the journal Science puts this enigma in perspective; for the last 7,000 years, New Zealand's largest glaciers have often moved out of step with glaciers in the Northern Hemisphere, pointing to strong regional variations in climate.
"This research should provide much more accurate reconstructions of glacial advances worldwide, allowing us in turn to make climate models more accurate," said Paul Filmer, program director in the National Science Foundation's (NSF) Division of Earth Sciences, which funded the research.
Conventional wisdom holds that during the era of human civilization, climate has been relatively stable. The new study is the latest to challenge this view, by showing that New Zealand's glaciers have gone through rapid periods of growth and decline during the current interglacial period known as the Holocene.
"New Zealand's mountain glaciers have fluctuated frequently over the last 7,000 years, and glacial advances have become slightly smaller through time," said Joerg Schaefer, lead author of the paper and a geochemist at Columbia University's Lamont-Doherty Earth Observatory.
"This pattern differs in important ways from the northern hemisphere glaciers. The door is open now towards a global map of Holocene [a geological time period that began about 11,700 years ago and continues to the present] glacier fluctuations and how climate variations during this period impacted human civilizations."
Glaciers are extremely sensitive to changes in temperature and snowfall, which makes them well suited for studying past climate. This archive has been largely untapped, however, because of the difficulty in assigning precise ages to glacier fluctuations.
One way to measure glacial fluxes is by studying the moraines, or rock deposits that glaciers often leave behind at their maximum points of advance.
However, until now the methods of dating such moraines, including radiocarbon dating of organic matter, could be off by hundreds of years.
By refining the analysis of a method called cosmogenic dating, Schaefer and colleagues were able for the first time to assign precise ages to young Holocene moraines.
They accomplished this by measuring minute levels of the chemical isotope beryllium 10 in the rocks, which is produced when cosmic rays strike rock surfaces, and builds up over time.
The researchers were thus able to pinpoint exactly when glaciers in New Zealand's Southern Alps began to recede, exposing the rocks to the cosmic rays.
From the results, they constructed a glacial timeline for the past 7,000 years and compared it against historic records from the Swiss Alps and other places north of the equator.
They found that within that timeframe, the glaciers around Mount Cook, New Zealand's highest peak, reached their largest extent about 6,500 years ago, when the Swiss Alps and Scandinavia were relatively warm.
That's about 6,000 years before northern glaciers hit their Holocene peak during the Little Ice Age, between 1300 and 1860 AD.
That finding was a surprise to some scientists who assumed that the northern cold phase happened globally. The record in New Zealand shows other disparities that point to regional climate variations in both hemispheres.
The new chemical and analytical protocols are expected to allow scientists to accurately date glacier fluctuations throughout the Holocene, rounding out the climate picture on the continents.
"With this measure we can go to almost any mountain range on earth and date the moraines in front of the glaciers and produce a similar chronology," said co-author George Denton, a glaciologist at the University of Maine and an adjunct scientist at Lamont-Doherty.
Overall, glaciers around the world have been declining since about 1860, with the exception of a brief advance in Switzerland in the 1980s, New Zealand in the late 1970s through today, and a few other places.
Changes in wind and sea surface temperatures are thought to be causing these regional fluctuations.
Currently in a wet phase, New Zealand is expected to swing back to a warmer, drier phase in the next few years, causing the glaciers to retreat once again.
The study also received funding from the Comer Science and Education Foundation, and the New Zealand Foundation for Research, Science and Technology.
Other researchers involved in the study were: Michael Kaplan and Roseanne Schwartz, also of Lamont-Doherty; Aaron Putnam, University of Maine; Robert Finkel, CEREGE, France; David Barrell, GNS Science, New Zealand; Bjorn Anderson, University of Oslo; Andrew Mackintosh, Victoria University of Wellington, New Zealand; Trevor Chinn, Alpine and Polar Processes Consultancy, New Zealand; Christian Schluchter, University of Bern, Switzerland.
Cheryl Dybas | EurekAlert!
Further reports about: > Alps > Earth's magnetic field > Glacial > Hemisphere > Holocene > New Zealand's largest glaciers > Northern hemisphere > climate models > cosmic ray > human civilization > moraines > mountain glaciers > rock deposits > sea surface temperature > southern hemisphere > world's glaciers are retreating
Filling the gap: High-latitude volcanic eruptions also have global impact
20.11.2017 | Institute of Atmospheric Physics, Chinese Academy of Sciences
Antarctic landscape insights keep ice loss forecasts on the radar
20.11.2017 | University of Edinburgh
The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.
Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
21.11.2017 | Physics and Astronomy
21.11.2017 | Physics and Astronomy
21.11.2017 | Life Sciences