Sune O. Rasmussen, A. Svensson and M. Polar ice cores reveal past climate change in ever-growing temporal resolution. Novel automated methods and improved manual annual layer identification allow for bipolar year-to-year investigations of climate events tens of thousands of years back in time. Ice cores from Antarctica, from the Greenland ice sheet, and from a number of smaller glaciers around the world yield a wealth of information on past climates and environments including unique records of past temperatures, atmospheric composition for example greenhouse gasses , volcanism, solar activity, dustiness, and biomass burning. Some ice-core records from Antarctica extend back in time more than , years Jouzel et al. For example, Greenland ice-core records reach back into the penultimate interglacial , years ago with annual or close to annual resolution NEEM community members To maximize the knowledge gain from ice cores it is essential to establish accurate and precise chronologies that assign an age to each depth segment.
Ice cores and climate change
The NEEM ice core is only used for supporting match-point identification. Over the uppermost Tephra horizons provide an independent validation of our match points. In addition, we compare the ratio of annual layer thicknesses between ice cores in-between the match points to assess our results in view of the different ice-flow patterns and accumulation regimes of the different periods and geographical regions. This initial timescale is the basis of interpretation and refinement of the presently derived EGRIP high-resolution data sets of chemical impurities.
Hence there are large dating uncertainties regarding glacial advance after the Eemian. Ice core dust records may complement this research.
The oldest ice core ever drilled outside the polar regions may contain ice that formed during the Stone Age — more than , years ago, long before modern humans appeared. Researchers from the United States and China are now studying the core — nearly as long as the Empire State Building is tall — to assemble one of the longest-ever records of Earth’s climate history. What they’ve found so far provides dramatic evidence of a recent and rapid temperature rise at some of the highest, coldest mountain peaks in the world.
The change is most noticeable on the Guliya Ice Cap, where they drilled the latest ice core. In this region, the average temperature has risen 1. Lonnie Thompson, Distinguished University Professor in the School of Earth Sciences at The Ohio State University and co-leader of the international research team, said that the new data lend support to computer models of projected climate changes. There, glaciologist Yao Tandong secured funding for a series of joint expeditions from the Chinese Academy of Sciences.
Continued warming in these regions will result in even more ice melt with the likelihood of catastrophic environmental consequences,” Yao noted. The name “Third Pole” refers to high mountain glaciers located on the Tibetan Plateau and in the Himalaya, in the Andes in South America, on Kilimanjaro in Africa, and in Papua, Indonesia — all of which have been studied by the Ohio State research team. Of particular interest to the researchers is a projection from the Intergovernmental Panel on Climate Change that future temperatures on the planet will rise faster at high altitudes than they will at sea level.
Ice Cores and the Age of the Earth
Ice cores are cylinders of ice drilled out of an ice sheet or glacier. Most ice core records come from Antarctica and Greenland, and the longest ice cores extend to 3km in depth. The oldest continuous ice core records to date extend , years in Greenland and , years in Antarctica. Ice cores contain information about past temperature, and about many other aspects of the environment. Crucially, the ice encloses small bubbles of air that contain a sample of the atmosphere — from these it is possible to measure directly the past concentration of gases including carbon dioxide and methane in the atmosphere.
Direct and continuous measurements of carbon dioxide CO 2 in the atmosphere extend back only to the s.
and volcanic ash: the importance of sparse tephras in Greenland ice cores. dated records from the Greenland GRIP, GISP2 and NGRIP ice cores for the past.
Deep ice core chronologies have been improved over the past years through the addition of new age constraints. However, dating methods are still associated with large uncertainties for ice cores from the East Antarctic plateau where layer counting is not possible. Consequently, we need to enhance the knowledge of this delay to improve ice core chronologies. It is especially marked during Dansgaard-Oeschger 25 where the proposed chronology is 2. Dating of 30m ice cores drilled by Japanese Antarctic Research Expedition and environmental change study.
Introduction It is possible to reveal the past climate and environmental change from the ice core drilled in polar ice sheet and glaciers. The 54th Japanese Antarctic Research Expedition conducted several shallow core drillings up to 30 m depth in the inland and coastal areas of the East Antarctic ice sheet. Ice core sample was cut out at a thickness of about 5 cm in the cold room of the National Institute of Polar Research, and analyzed ion, water isotope, dust and so one.
We also conducted dielectric profile measurement DEP measurement. The age as a key layer of large-scale volcanic explosion was based on Sigl et al. Nature Climate Change,
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.
Dating of Greenland Ice Cores by Flow Models, Isotopes, Volcanic Debris, and Continental Dust – Volume 20 Issue 82 – C.U. Hammer, H. B.
Ice core , long cylinder of glacial ice recovered by drilling through glaciers in Greenland, Antarctica , and high mountains around the world. Scientists retrieve these cores to look for records of climate change over the last , years or more. Ice cores were begun in the s to complement other climatological studies based on deep-sea cores, lake sediments, and tree-ring studies dendrochronology. Since then, they have revealed previously unknown details of atmospheric composition , temperature, and abrupt changes in climate.
Abrupt changes are of great concern for those who model future changes in climate and their potential impacts on society. Ice cores record millennia of ancient snowfalls, which gradually turned to crystalline glacier ice. In areas of high accumulation, such as low-latitude mountain glaciers and the Greenland Ice Sheet , annual layers of ice representing tens of thousands of years can be seen and counted, often with the unaided eye.
The first deep drilling took place in the s as preliminary efforts at Camp Century, Greenland, and Byrd Station, Antarctica.
Core questions: An introduction to ice cores
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. Climate models project that if emissions continue, by , Greenland temperatures will exceed anything seen since the last interglacial period , around , years ago.
Widespread thermometer measurements of temperatures only extend back to the mids.
Ethane measurements in Greenland ice cores: Developing a preindustrial record Cosmogenic surface exposure dating of Arctic NW Laurentide ice-sheet.
Polar ice results from the progressive densification of snow deposited at the surface of the ice sheet. The transformation of snow into ice generally occurs within the first meters and takes from decades to millennia, depending on temperature and accumulation rate, to be completed. During the first stage of densification, recrystallization of the snow grains occurs until the closest dense packing stage is reached at relative densities of about 0.
Then plastic deformation becomes the dominant process and the pores progressively become isolated from the surface atmosphere. The end product of this huge natural sintering experiment is ice, an airtight material. Because of the extreme climatic conditions, the polar ice is generally kept at negative temperatures well below the freezing point, a marked difference to the ice of temperate mountain glaciers. Skip to main content Skip to table of contents.
An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier. Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper, and an ice core contains ice formed over a range of years. Cores are drilled with hand augers for shallow holes or powered drills; they can reach depths of over two miles 3. The physical properties of the ice and of material trapped in it can be used to reconstruct the climate over the age range of the core.
The proportions of different oxygen and hydrogen isotopes provide information about ancient temperatures , and the air trapped in tiny bubbles can be analysed to determine the level of atmospheric gases such as carbon dioxide. Since heat flow in a large ice sheet is very slow, the borehole temperature is another indicator of temperature in the past.
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.
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. But 14 C is not the only cosmogenic isotope produced by such high energy events.
Specifically, Beryllium 10 Be is formed from high energy collisions with N and O in the atmosphere, and because of its long lifetime and affinity for soluble aerosols, it precipitates out of the atmosphere quickly and can be measured in ice cores.