An ice core is a cylinder shaped sample of ice drilled from a glacier. Ice core records provide the most direct and detailed way to investigate past climate and atmospheric conditions. Snowfall that collects on glaciers each year captures atmospheric concentrations of dust, sea-salts, ash, gas bubbles and human pollutants. Analysis of the. Ice core records can be used to reconstruct temperature, atmospheric circulation strength, precipitation, ocean volume, atmospheric dust, volcanic eruptions, solar variability, marine biological productivity, sea ice and desert extent, and forest fires. Examples of aerosols and chemical elements that are transported and deposited on ice sheets and glaciers. Seasonal markers such as stable isotope ratios of water vary depending on temperature and can reveal warmer and colder periods of the year.
Antarctic Ice Cores and Environmental Change
To support our nonprofit science journalism, please make a tax-deductible gift today. Scientists endured bitter winds to retrieve ancient ice from a blue ice field in the Allan Hills of Antarctica. Scientists announced today that a core drilled in Antarctica has yielded 2.
demonstrating synchrony of climate changes over broad regions. Ice-Core Interpretation. Dating and Accumulation. On some glaciers and ice sheets, sufficient.
Ice consists of water molecules made of atoms that come in versions with slightly different mass, so-called isotopes. Variations in the abundance of the heavy isotopes relative to the most common isotopes can be measured and are found to reflect the temperature variations through the year. The graph below shows how the isotopes correlate with the local temperature over a few years in the early s at the GRIP drill site:.
The dashed lines indicate the winter layers and define the annual layers. How far back in time the annual layers can be identified depends on the thickness of the layers, which again depends on the amount of annual snowfall, the accumulation, and how deep the layers have moved into the ice sheet. As the ice layers get older, the isotopes slowly move around and gradually weaken the annual signal.
Read more about – diffusion of stable isotopes – how the DYE-3 ice core has been dated using stable isotope data – how stable isotope measurements are performed – stable isotopes as indicators of past temperatures – how annual layers are identified using impurity data. Move the mouse over individual words to see a short explanation of the word or click on the word to go to the relevant page. For more information on the topic please contact Bo Vinther. Centre for Ice and Climate. Ice Core Drilling Projects.
How do scientists use ice cores to determine past climates?
Research article 10 Jan Correspondence : Pascal Bohleber pascal. This unique long-term archive is the result of an exceptionally low net accumulation driven by wind erosion and rapid annual layer thinning. However, the full exploitation of the CG time series has been hampered by considerable dating uncertainties and the seasonal summer bias in snow preservation. Glaciers and ice caps of high mountain ranges can provide climate records of mid- and low latitudes complementary to polar ice cores.
In comparison to their polar counterparts, mountain drilling sites are characterized by a comparatively small-scale glacier geometry and their proximity to continental source areas.
Ice cores from the Greenland and Antarctic ice sheets provide highly resolved, well-dated climate records of past polar temperatures, atmospheric.
Alley, R. Download references. Reprints and Permissions. Hammer, C.
Dating ice cores
It is not uncommon to read that ice cores from the polar regions contain records of climatic change from the distant past. Research teams from the United States, the Soviet Union, Denmark, and France have bored holes over a mile deep into the ice near the poles and removed samples for analysis in their laboratories. Based on flow models, the variation of oxygen isotopes, the concentration of carbon dioxide in trapped air bubbles, the presence of oxygen isotopes, acid concentrations, and particulates, they believe the lowest layers of the ice sheets were laid down over , years ago.
The ice could be dated with an accuracy of approximately ±2 years to a depth of m (which corresponds to the year ) by counting seasonal variations in.
And it is ice that draws paleoclimatologists literally to the ends of the Earth in the quest for knowledge about where our planet has been, where it is, and where it might be going. Ice cores provide a unique contribution to our view of past climate because the bubbles within the ice capture the gas concentration of our well-mixed atmosphere while the ice itself records other properties. Scientists obtain this information by traveling to ice sheets, like Antarctica or Greenland, and using a special drill that bores down into the ice and removes a cylindrical tube called an ice core.
Drilling thousands of meters into ice is a feat of technology, endurance, and persistence in extreme environments, exemplified by the joint Russian, U. In , Russian scientists extended the ice core to an incredible 3, meters, reaching Lake Vostok underneath the East Antarctic Ice Sheet. After scientists procure the cores, they slice them up into various portions each allotted to a specific analytical or archival purpose. As the scientists are dividing the cores for analysis, they don special clean suits to prevent the core samples from becoming contaminated.
Once the samples have been prepared, the scientists run a variety of physical and chemical analyses on the cores. Some of these ice procedures are consumptive, meaning their analysis requires destruction of the ice, while others have no effect on the ice. Scientists study the gas composition of the bubbles in the ice by crushing a sample of the core in a vacuum. Overall, most of the core is reserved for archival purposes, preserving a long record of Earth history for future research.
These cores have distinct layers in them that form throughout the years. With each passing year, snow falls over the ice sheets and each layer of snow has a different texture and a different chemistry, with winter snow differing from summer snow as well. During the summer, when the sun is up for 24 hours many days, the top layer of the snow changes in texture.
Core questions: An introduction to ice cores
Figure 1 Scientists measure ice cores from deep drilling sites on the ice sheet near Casey station Photo by M. Antarctica is the coldest, windiest, highest and driest continent on Earth. That’s right – the driest! Antarctica is a desert. The annual precipitation of snow, averaged across the continent, is about 30 centimetres, which is equivalent to about 10 centimetres of water. In some locations as little as 2 centimetres water equivalent is recorded.
Ice core dating using stable isotope data. Ice consists of water molecules made of atoms that come in versions with slightly different mass, so-called isotopes.
Astronomy in Space with David Dickinson. By: David Dickinson May 14, 1. You can unsubscribe anytime. You never know where an astronomical event might turn up in old historical records, and how it might link up with evidence from modern science. Researchers at the University of Geneva recently uncovered such an astronomical tale from the archives, using contemporary accounts of a curiously dark lunar eclipse to give insight into volcanic eruptions and their effect medieval climate.
The researchers, who published their study April 21st in Scientific Reports , were examining ice cores from Greenland and Antarctica over the past couple millennia, looking for sulfate spikes that would indicate volcanic eruptions. These spikes had usually been ascribed to the AD eruption of the Hekla volcano in Iceland, but a study by climate researcher Michael Sigl University of Bern, Switzerland suggested that the timing was off, and that the real culprit was a tropical eruption around AD.
To do that, the researchers looked to another unique event that transpired around the same time: a total eclipse of the Moon on May 5, Astronomers have long known of the bizarre “dark eclipse” of AD.
Stratigraphy and dating
Find out why ice core research is so important for our understanding of climate change and how we drill and analyse the ice cores. For a detailed look at how ice cores are recovered from Antarctica watch this video. Why do scientists drill ice cores? What makes ice cores so useful for climate research?
), while ice cores from sites with higher accumu- lation offer continuous records of very high temporal resolution. For example, Greenland ice-core records.
Guest commentary from Jonny McAneney. You heard it here first …. Back in February, we wrote a post suggesting that Greenland ice cores may have been incorrectly dated in prior to AD This was based on research by Baillie and McAneney which compared the spacing between frost ring events physical scarring of living growth rings by prolonged sub-zero temperatures in the bristlecone pine tree ring chronology, and spacing between prominent acids in a suite of ice cores from both Greenland and Antarctica.
Last month, in an excellent piece of research Sigl et al. The clinching evidence was provided by linking tree-ring chronologies to ice cores through two extraterrestrial events…. In , Miyaki et al. The cause of this increase was possibly due to a very high energy solar proton event Usoskin et al.
Ice core basics
Based on an early Greenland ice core record produced back in , versions of the graph have, variously, mislabeled the x-axis, excluded the modern observational temperature record and conflated a single location in Greenland with the whole world. More recently, researchers have drilled numerous additional ice cores throughout Greenland and produced an updated estimate past Greenland temperatures.
This modern temperature reconstruction, combined with observational records over the past century, shows that current temperatures in Greenland are warmer than any period in the past 2, years. However, warming is expected to continue in the future as human actions continue to emit greenhouse gases, primarily from the combustion of fossil fuels.
Note that methods based on radioactive decay are not of use to date polar ice directly. In particular, 14C dating of the CO2 trapped in air bubbles is possible but.
Why use ice cores? How do ice cores work? Layers in the ice Information from ice cores Further reading References Comments. Current period is at right. Wikimedia Commons. Ice sheets have one particularly special property. They allow us to go back in time and to sample accumulation, air temperature and air chemistry from another time. Ice core records allow us to generate continuous reconstructions of past climate, going back at least , years.