— Ice sheets are like bulldozers. As they grow, they push rocks, boulders, clams, fossils and other debris into piles called moraines.
Credit: Jason Briner
Shells from Greenland. By dating fossils like these, scientists have come up with a new technique for determining when glaciers were smaller than they are today.
— By dating ancient clams in moraines, scientists have come up with a new technique for determining when glaciers were smaller than they are today.
— The technique suggests that the Greenland Ice Sheet was at its smallest point in recent history 3-5,000 years ago — information that could improve our understanding of how ice responds to climate change.
Think Greenland’s ice sheet is small today?
It was smaller — as small as it has ever been in recent history — from 3-5,000 years ago, according to scientists who studied the ice sheet’s history using a new technique they developed for interpreting the Arctic fossil record.
“What’s really interesting about this is that on land, the atmosphere was warmest between 9,000 and 5,000 years ago, maybe as late as 4,000 years ago. The oceans, on the other hand, were warmest between 5-3,000 years ago,” said Jason Briner, PhD, University at Buffalo associate professor of geology, who led the study.
“What it tells us is that the ice sheets might really respond to ocean temperatures,” he said. “It’s a clue to what might happen in the future as the Earth continues to warm.”
The findings appeared online on Nov. 22 in the journal Geology. Briner’s team included Darrell Kaufman, an organic geochemist from Northern Arizona University; Ole Bennike, a clam taxonomist from the Geological Survey of Denmark and Greenland; and Matthew Kosnik, a statistician from Australia’s Macquarie University.
The study is important not only for illuminating the history of Greenland’s ice sheet, but for providing geologists with an important new tool: A method of using Arctic fossils to deduce when glaciers were smaller than they are today.
Scientists have many techniques for figuring out when ice sheets were larger, but few for the opposite scenario.
“Traditional approaches have a difficult time identifying when ice sheets were smaller," Briner said. "The outcome of our work is that we now have a tool that allows us to see how the ice sheet responded to past times that were as warm or warmer than present — times analogous to today and the near future."
The technique the scientists developed involves dating fossils in piles of debris found at the edge of glaciers.
To elaborate: Growing ice sheets are like bulldozers, pushing rocks, boulders and other detritus into heaps of rubble called moraines.
Because glaciers only do this plowing when they're getting bigger, logic dictates that rocks or fossils found in a moraine must have been scooped up at a time when the associated glacier was older and smaller.
So if a moraine contains fossils from 3,000 years ago, that means the glacier was growing — and smaller than it is today — 3,000 years ago.
This is exactly what the scientists saw in Greenland: They looked at 250 ancient clams from moraines in three western regions, and discovered that most of the fossils were between 3-5,000 years old.
The finding suggests that this was the period when the ice sheet’s western extent was at its smallest in recent history, Briner said.
“Because we see the most shells dating to the 5-3000-year period, we think that this is when the most land was ice-free, when large layers of mud and fossils were allowed to accumulate before the glacier came and bulldozed them up,” he said.
Because radiocarbon dating is expensive, Briner and his colleagues found another way to trace the age of their fossils.
Their solution was to look at the structure of amino acids — the building blocks of proteins — in the fossils of ancient clams. Amino acids come in two orientations that are mirror images of each other, known as D and L, and living organisms generally keep their amino acids in an L configuration.
When organisms die, however, the amino acids begin to flip. In dead clams, for example, D forms of aspartic acid start turning to L’s.
Because this shift takes place slowly over time, the ratio of D’s to L’s in a fossil is a giveaway of its age.
Knowing this, Briner’s research team matched D and L ratios in 20 Arctic clamshells to their radiocarbon-dated ages to generate a scale showing which ratios corresponded with which ages. The researchers then looked at the D and L ratios of aspartic acid in the 250 Greenland clamshells to come up with the fossils’ ages.
Amino acid dating is not new, but applying it to the study of glaciers could help scientists better understand the history of ice — and climate change — on Earth.
The study was funded by the National Geographic Society and U.S. National Science Foundation.
Gas hydrate research: Advanced knowledge and new technologies
23.03.2018 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ
New technologies and computing power to help strengthen population data
22.03.2018 | University of Southampton
Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.
The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...
An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.
The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
23.03.2018 | Event News
19.03.2018 | Event News
16.03.2018 | Event News
23.03.2018 | Materials Sciences
23.03.2018 | Agricultural and Forestry Science
23.03.2018 | Physics and Astronomy