Jump to navigation. Posted by Don Keyes on September 03, at Do you know if ice core dating is accurate. I heard that Antarctica had ice rings like tree rings that go back 50, years undisturbed by a flood. If it is challenged do you know on what basis.
Thus the snow has accumulated year after year for thousands of years and, with time, is compressed to ice to form the Antarctic ice sheet. Approximately 98 per cent of the Antarctic continent is covered by the ice sheet which is on average about 2, metres thick and, at it's deepest location, 4, metres thick. It is due to this thick ice mass that Antarctica is, on average, the highest continent.
Since the ice sheet is formed by the accumulation of snow year after year, by drilling from the surface down through the ice sheet, we drill our way back in time. Ice drills are designed to collect a core as they cut through the ice, so samples are collected that are made up of ice deposited in the form of snow many thousands of years ago. As the snow is deposited on top of the ice sheet each year, it traps different chemicals and impurities which are dissolved in the ice.
The ice and impurities hold information about the Earth's environment and climate at the time of deposition. A variety of different analyses techniques are used to extract that information. One measurement, the oxygen isotope ratio or delta value, measured using a mass spectrometer on melted samples of the ice, gives us an indication of the temperature at the time the ice was deposited as snow.
Measuring the delta value at many depths through the ice core is equivalent to measuring the air temperature at many times in the past. Thus, a climatic history is developed. Climatic temperature against time from delta measurements taken on the ice core drilled at the Russian station, Vostok, in central Antarctica Figure 2. Available data from this ice core so far extends back aboutyears. However, drilling of the core still continues, and it is expected that, when drilling is completed in a few years time, an age ofyears will have been reached.
This was an ice age period. These short warmer periods are called inter-glacials. We are in an inter-glacial now.
Fromto about 20, years ago, there was a long period of cooling temperatures, but with some ups and downs of a degree or two. From about 18, or 19, years ago to about 15, years ago, the climate went through another warming period to the next inter-glacial, - the one we are now in. What is being seen here is two possible ice ages, the first one being somewhat less and perhaps shorter than the second.
Removing the time element, which is gradualistic and uniformitarian, what might just as easily be seen is the ice age that is postulated as arising out of the Flood catastrophe, with a warmer period for several hundred years, and then the massive volcanic activity thought to be present at the time of Peleg, which would have resulted in a much more severe ice age.
During the formation of both ice ages, the storms would have had to be constant, one on top of another with very little time in between, and very fierce. This would also account for what is seen in the ice cores.
Ice core dating isotopes
Figure 2 also includes a graph of the concentration of dust in the ice core. High concentrations of dust occur at the same times as the colder periods shown on the temperature graph.
There are several possible reasons for this: the air is drier during colder periods, thus, there may have been more deserts; the ice sheets were more extensive and sea levels lower, thus there would have been more exposed, dry land; there may also have been more storms, or at least more violent storms. All of these factors would increase the amount of dust lifted into the atmosphere to then be blown over Antarctica and deposited with the snow on the surface of the ice sheet.
Colder periods are normally times of less precipitation, as cold air is dry. The writer here is postulating more deserts by presuming a worldwide cold and dry climate. I think he may be presuming too much. A warmer world in the tropic and temperate zones, particularly where the oceans are concerned a few degrees warmer temperature in the oceans would vastly increase the rate of evaporationwould provide the precipitation for the massive snowfalls required for the laying down of not only the polar caps but for the advent of the ice age s as well.
One thing I noticed here is that the author also mentions more land being exposed during the ice age sand when I mentioned that, I was ridiculed on this forum. One thing that is not mentioned in this article is the composition of the dust. Does it show high or low amounts of volcanic material? And at which levels? I would be curious to know this.
Figure 2. Dust concentration, climatic air temperature as inferred from del measurementsand concentration of carbon dioxide and methane from measurements of trapped air are plotted against time before present. After Lorius et al. The snow near the surface of the ice sheet is like a sponge with channels of air between the snow grains.
As more and more snow is accumulated on top, the underlying snow is compressed into ice and the air forms bubbles in the ice. Ice cores therefore can be analysed not just for the chemical and physical properties of the ice, but also for the properties of the air trapped in the ice. These bubbles are actual samples of the atmosphere up to thousands of years ago. So, analysis of them can tell us much about the atmosphere in the past.
Concentrations of carbon dioxide and methane measured in the air bubbles trapped in the ice are shown in Figure 2 along with temperature and dust graphs. Carbon dioxide and methane are greenhouse gases and the similarity between the graphs for their concentrations and the temperature change graph indicates that the greenhouse effect is real and that it has been around for many thousands of years.
That is only if you are presuming many thousands of years. I studied that chart for some time. What I saw corresponds to the idea that a post flood ice age would have less dust due to winds because everything was wet. But then you have that period in between ice ages where you see a rise in carbon dioxide as the plant life on earth was re-established and thrived. This corresponds with the rapid rise in temperature which melted the ice. Now, keep in mind that we are ONLY talking about the one pole here - the south one.
These measurements do NOT tell us what the rest of the world was like at the time. As we move to the left in graph two, or toward the present, there is a sudden rise in the dust factor.
This would easily result from volcanism and the changes in relative air temperatures, and even changes in relative areas of sea temperatures, around the world. The would cause the massive winds that seek to equalize the temperatures.
More dust at a time of increasing cold and the rapid onset of a much worse ice age. Then, to the far left of the graph, a rapid rise in temperature again as the dust settles down and the temperatures and thus the pressures have also settled.
The earth warms again and the ices melt, leaving what is left on the poles. You see, if one does not presume long ages, many rapid storms in a time of fluctuating temperatures and world upheaval can account for what we see in that graph. Has there been a significant increase in the atmospheric concentration of greenhouse gases since the industrial revolution? The answer is yes, as can be seen from Figure 3 which shows the concentrations of carbon dioxide in the atmosphere, measured in the bubbles from an Antarctic ice core from Law Dome near Australia's Casey Station.
The concentration of carbon dioxide has increased from about parts per million to parts per million, which is a rise of 25 per cent since the middle of last century. Nitrous oxide and other greenhouse gases also show similar trends from analysis of the ice-core bubbles.
The Law Dome ice core is at a location where the snow accumulation is much higher than at Vostok. Thus, the time scale for the Law Dome core is expanded and it can provide us with more detailed information about recent climate changes, though it can not go back in time as far as the deeper Vostok ice core.
By sampling at very fine intervals down the ice core, and provided that each annual layer of snow is thick enough, several samples from each year may be measured for the different chemical properties.
It has already been seen that the delta value is related to air temperature when the snow was deposited. Because it is warmer in summer and cooler in winter, and provided the snow layers are not too disturbed by wind, the delta value can show annual cycles. Thus, these values can be used to date the ice core. Hydrogen peroxide is created in the atmosphere by a chemical reaction that requires ultraviolet light.
There is a lot less ultraviolet light in the winter than in the summer in Antarctica. Thus, measurements of hydrogen peroxide dissolved in the ice also provide a good annual cycle indicator.
Some observations here: first of all the dust would have had to be produced by winds bringing it in. Therefore the pattern is upset from the outset. Secondly, it is presumed that the variations in temperatures are correlative to summer and winter variations.
However this does not necessarily have to be the case. Uniformitarian gradualism is a presumption which rests on a shaky foundation here simply because of the presence of the varying amount of dust if nothing else! The only thing indicating "annual" cycles in the ice core is the presumption of the person interpreting the data.
In order to date the ice cores accurately, the annual layers need to be thick enough to obtain about ten measurement samples from each year. The thickness of the annual layers depends on how much snow falls each year.
Future of ice core laboratory and its evidence in doubt
Thus, to obtain an ice core from which accurate, detailed dating can be derived, we need to find an Antarctic site where the snow accumulation is relatively high. If the aircraft were buried under about feet of ice and snow in about 50 years, this means the ice sheet has been accumulating at an average rate of five feet per year.
The Greenland ice sheet averages almost feet thick. If we were to assume the ice sheet has been accumulating at this rate since its beginning, it would take less than years for it to form and the recent-creation model might seem to be vindicated. However, life is never as simple as implied above. In making our calculations, we did not take into account the compaction of the snow into ice as it is weighted down by the snow above.
Neither did we consider the thinning of ice layers as the tremendous weight above forces the ice at lower levels to squeeze out horizontally. More importantly, we did not consider the average precipitation rate and actual depths of ice for different locations on the Greenland ice sheet.
When these factors are taken into account, the average annual thickness of ice at Camp Century located near the northern tip of Greenland is believed to vary from about fourteen inches near the surface to less than two inches near the bottom Hammer, et al. If, for simplicity, we assume the average annual thickness to be the mean between the annual thickness at the top and at the bottom about eight inchesthis still gives an age of less than years for the foot-thick ice sheet to form under uniformitarian conditions.
Although occasional ambiguities occur, it is relatively easy to count annual layers downward from the surface through considerable depths in the Greenland ice sheet. This is possible because of the large precipitation rates in Greenland and the preservation of the annual effects. It is also possible with a high degree of accuracy to cross check the counting of annual layers with occasional peaks in acidity and particulates from the fallout of historic volcanic events.
Hammer, et al. About a dozen historical volcanic eruptions are evident in the ice core from Crete in central Greenland. Several unknown eruptions are also documented in the ice core record. The confidence in the chronology becomes less the lower in the ice sheet one goes, however. The amplitude of the annual oscillations slowly decreases relative to other factors, and historic markers are fewer and farther apart. Glaciologists estimate that uncertainties in identification of layers will probably limit the number of countable layers to less than about 8, Hammer, et al.
The claims that layers of ice were forme years ago or more come primarily from interpretation of ice cores in Antarctica Jouzel, et al. The Soviet Antarctic Expeditions at Vostok in East Antarctica recovered an ice core which was almost 7, feet long in a region where the total ice thickness is about 12, feet Lorius, et al.
Since the current precipitation rate is so much less than Greenland on the order of one inch per year the crude calculation of age, without corrections for compression and horizontal motion for the lowest layers is more thanyears. However, such estimates are critically based on the assumption that the accumulation rate has not varied greatly over the past. In Greenland, the high precipitation rates not only provide relatively thick annual layers for analysis, but the accumulating snow quickly seals off the ice beneath and protects the record from metamorphosis by pressure and temperature changes in the atmosphere.
In Antarctica, by the time the ice has been buried deeply enough to no longer be influenced by the atmosphere, annual variations have been greatly dampened by diffusion Epstein, et al. Through a second-known relation between temperature and precipitation rate, again observed in today's atmosphere, the accumulation rate for a given layer is calculated Lorius, et al.
Once the accumulation rate is calculated for each layer, the depth and age for each layer in the ice is calculated by integrating the annual accumulation downward from the surface.
There are several historical markers in Antarctica which can be used to cross check these calculations for the past few thousand years. But historical volcanic events are not known beyond a few thousand years in the past which provide any certainty to the calculation of age. This method would be reasonably reliable if precipitation rates had been similar in the past.
However, some creationist models predict significant quantities of snow immediately after the Flood Oard, From a creationist perspective, it would be extremely valuable to thoroughly explore these ice-core data. We would not assume that the precipitation rate has always been similar to that of today.
We would expect considerably higher precipitation rates immediately following the Flood. The "annual" layers deep in the Greenland ice sheet may be related to individual storms rather than seasonal accumulations. The drill removes an annulus of ice around the core but does not cut under it.
A spring-loaded lever arm called a core dog can break off the core and hold it in place while it is brought to the surface.
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The core is then extracted from the drill barrel, usually by laying it out flat so that the core can slide out onto a prepared surface. The surface that receives the core should be aligned as accurately as possible with the drill barrel to minimise mechanical stress on the core, which can easily break.
The ambient temperature is kept well below freezing to avoid thermal shock. A log is kept with information about the core, including its length and the depth it was retrieved from, and the core may be marked to show its orientation. It is usually cut into shorter sections, the standard length in the US being one metre.
The cores are then stored on site, usually in a space below snow level to simplify temperature maintenance, though additional refrigeration can be used. If more drilling fluid must be removed, air may be blown over the cores. Any samples needed for preliminary analysis are taken. The core is then bagged, often in polytheneand stored for shipment.
Sep 20, The water molecules in ice cores are always depleted in the heavier isotopes (that is, the isotopes with the larger number of neutrons) and the difference compared to the standard is expressed as. Ice core dating isotopes - How to get a good woman. It is not easy for women to find a good man, and to be honest it is not easy for a man to find a good woman. Register and search over 40 million singles: voice recordings. Is the number one destination for online dating with more relationships than any other dating or personals site. Other ways of dating ice cores include geochemisty, wiggle matching of ice core records to insolation time series (Lemieux-Dudon et al. ), layers of volcanic ash (tephra) (Vinther et al., ), electrical conductivity, and using numerical flow models to understand age-depth relationships (Mulvaney et al., ), combined with firn.
Additional packing, including padding material, is added. When the cores are flown from the drilling site, the aircraft's flight deck is unheated to help maintain a low temperature; when they are transported by ship they must be kept in a refrigeration unit.
There are several locations around the world that store ice cores, such as the National Ice Core Laboratory in the US. These locations make samples available for testing. A substantial fraction of each core is archived for future analyses. Over a depth range known as the brittle ice zone, bubbles of air are trapped in the ice under great pressure. When the core is brought to the surface, the bubbles can exert a stress that exceeds the tensile strength of the ice, resulting in cracks and spall.
The brittle ice zone typically returns poorer quality samples than for the rest of the core. Some steps can be taken to alleviate the problem. Liners can be placed inside the drill barrel to enclose the core before it is brought to the surface, but this makes it difficult to clean off the drilling fluid. In mineral drilling, special machinery can bring core samples to the surface at bottom-hole pressure, but this is too expensive for the inaccessible locations of most drilling sites.
Keeping the processing facilities at very low temperatures limits thermal shocks. Extruding the core from the drill barrel into a net helps keep it together if it shatters. Brittle cores are also often allowed to rest in storage at the drill site for some time, up to a full year between drilling seasons, to let the ice gradually relax.
Many different kinds of analysis are performed on ice cores, including visual layer counting, tests for electrical conductivity and physical properties, and assays for inclusion of gases, particles, radionuclidesand various molecular species. For the results of these tests to be useful in the reconstruction of palaeoenvironmentsthere has to be a way to determine the relationship between depth and age of the ice.
The simplest approach is to count layers of ice that correspond to the original annual layers of snow, but this is not always possible. An alternative is to model the ice accumulation and flow to predict how long it takes a given snowfall to reach a particular depth. Another method is to correlate radionuclides or trace atmospheric gases with other timescales such as periodicities in the earth's orbital parameters.
A difficulty in ice core dating is that gases can diffuse through firn, so the ice at a given depth may be substantially older than the gases trapped in it.
As a result, there are two chronologies for a given ice core: one for the ice, and one for the trapped gases. To determine the relationship between the two, models have been developed for the depth at which gases are trapped for a given location, but their predictions have not always proved reliable.
The density and size of the bubbles trapped in ice provide an indication of crystal size at the time they formed. The size of a crystal is related to its growth rate, which in turn depends on the temperature, so the properties of the bubbles can be combined with information on accumulation rates and firn density to calculate the temperature when the firn formed. Radiocarbon dating can be used on the carbon in trapped CO 2.
The CO 2 can be isolated by subliming the ice in a vacuum, keeping the temperature low enough to avoid the loess giving up any carbon.
A. Introduction Learning outcomes - You should be able to: describe methods for dating ice cores; predict relative changes in global temperatures based on ice core analysis of greenhouse gasses and isotopes of oxygen and hydrogen;. 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. 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. Introduction 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 .
The results have to be corrected for the presence of 14 C produced directly in the ice by cosmic rays, and the amount of correction depends strongly on the location of the ice core. Corrections for 14 C produced by nuclear testing have much less impact on the results.
The very small quantities typically found require at least g of ice to be used, limiting the ability of the technique to precisely assign an age to core depths. Timescales for ice cores from the same hemisphere can usually be synchronised using layers that include material from volcanic events.
It is more difficult to connect the timescales in different hemispheres.
The Laschamp eventa geomagnetic reversal about 40, years ago, can be identified in cores;   away from that point, measurements of gases such as CH 4 methane can be used to connect the chronology of a Greenland core for example with an Antarctic core. This approach was developed in and has since been turned into a software tool, DatIce. The boundary between the Pleistocene and the Holoceneabout 11, years ago, is now formally defined with reference to data on Greenland ice cores.
Formal definitions of stratigraphic boundaries allow scientists in different locations to correlate their findings. These often involve fossil records, which are not present in ice cores, but cores have extremely precise palaeoclimatic information that can be correlated with other climate proxies. The dating of ice sheets has proved to be a key element in providing dates for palaeoclimatic records. Cores show visible layers, which correspond to annual snowfall at the core site.
If a pair of pits is dug in fresh snow with a thin wall between them and one of the pits is roofed over, an observer in the roofed pit will see the layers revealed by sunlight shining through. A six-foot pit may show anything from less than a year of snow to several years of snow, depending on the location.
Poles left in the snow from year to year show the amount of accumulated snow each year, and this can be used to verify that the visible layer in a snow pit corresponds to a single year's snowfall.
In central Greenland a typical year might produce two or three feet of winter snow, plus a few inches of summer snow.
Ice Cores and the Age of the Earth
When this turns to ice, the two layers will make up no more than a foot of ice. The layers corresponding to the summer snow will contain bigger bubbles than the winter layers, so the alternating layers remain visible, which makes it possible to count down a core and determine the age of each layer.
Dust layers may now become visible. Ice from Greenland cores contains dust carried by wind; the dust appears most strongly in late winter, and appears as cloudy grey layers. These layers are stronger and easier to see at times in the past when the earth's climate was cold, dry, and windy.
Any method of counting layers eventually runs into difficulties as the flow of the ice causes the layers to become thinner and harder to see with increasing depth. When there is summer melting, the melted snow refreezes lower in the snow and firn, and the resulting layer of ice has very few bubbles so is easy to recognise in a visual examination of a core.
MF calculations are averaged over multiple sites or long time periods in order to smooth the data. Plots of MF data over time reveal variations in the climate, and have shown that since the late 20th century melting rates have been increasing. In addition to manual inspection and logging of features identified in a visual inspection, cores can be optically scanned so that a digital visual record is available.
This requires the core to be cut lengthwise, so that a flat surface is created. The isotopic composition of the oxygen in a core can be used to model the temperature history of the ice sheet. Oxygen has three stable isotopes, 16 O17 O and 18 O. At lower temperatures, the difference is more pronounced. If the site has experienced significant melting in the past, the borehole will no longer preserve an accurate temperature record.
Hydrogen ratios can also be used to calculate a temperature history. Deuterium 2 Hor D is heavier than hydrogen 1 H and makes water more likely to condense and less likely to evaporate. It was once thought that this meant it was unnecessary to measure both ratios in a given core, but in Merlivat and Jouzel showed that the deuterium excess reflects the temperature, relative humidity, and wind speed of the ocean where the moisture originated.
Since then it has been customary to measure both.
Water isotope records, analyzed in cores from Camp Century and Dye 3 in Greenland, were instrumental in the discovery of Dansgaard-Oeschger events -rapid warming at the onset of an interglacialfollowed by slower cooling.
Combining this information with records of carbon dioxide levels, also obtained from ice cores, provides information about the mechanisms behind changes in CO 2 over time. It was understood in the s that analyzing the air trapped in ice cores would provide useful information on the paleoatmospherebut it was not until the late s that a reliable extraction method was developed.
Further research has demonstrated a reliable correlation between CO 2 levels and the temperature calculated from ice isotope data. Because CH 4 methane is produced in lakes and wetlandsthe amount in the atmosphere is correlated with the strength of monsoonswhich are in turn correlated with the strength of low-latitude summer insolation.
The ice core is cleaned before sawing the ice into 2 meter sections The cloudy layers visible in this 6 meter core section were formed when dust fell onto the ice sheet and was entrained in the ice What do isotopes have to do with ice cores? Ice Core Dating. By sampling at very fine intervals down the ice core, and provided that each annual layer of snow is thick enough, several samples from each year may be measured for the different chemical properties. It has already been seen that the delta value is related to air temperature when the snow was deposited. Ice core, long cylinder of glacial ice recovered by drilling through glaciers in Greenland, Antarctica, and high mountains around the jankossencontemporary.comists 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.
Since insolation depends on orbital cyclesfor which a timescale is available from other sources, CH 4 can be used to determine the relationship between core depth and age. This means that the trapped air retains, in the ratio of O 2 to N 2a record of the summer insolation, and hence combining this data with orbital cycle data establishes an ice core dating scheme.
Diffusion within the firn layer causes other changes that can be measured. Gravity causes heavier molecules to be enriched at the bottom of a gas column, with the amount of enrichment depending on the difference in mass between the molecules. Colder temperatures cause heavier molecules to be more enriched at the bottom of a column.
Greenland cores, during times of climatic transition, may show excess CO2 in air bubbles when analysed, due to CO2 production by acidic and alkaline impurities .
Summer snow in Greenland contains some sea salt, blown from the surrounding waters; there is less of it in winter, when much of the sea surface is covered by pack ice. Similarly, hydrogen peroxide appears only in summer snow because its production in the atmosphere requires sunlight.
These seasonal changes can be detected because they lead to changes in the electrical conductivity of the ice. Placing two electrodes with a high voltage between them on the surface of the ice core gives a measurement of the conductivity at that point.
Dragging them down the length of the core, and recording the conductivity at each point, gives a graph that shows an annual periodicity. Such graphs also identify chemical changes caused by non-seasonal events such as forest fires and major volcanic eruptions. When a known volcanic event, such as the eruption of Laki in Iceland incan be identified in the ice core record, it provides a cross-check on the age determined by layer counting. If the date of the eruption is not known, but it can be identified in multiple cores, then dating the ice can in turn give a date for the eruption, which can then be used as a reference layer.
Many other elements and molecules have been detected in ice cores. Both hydrogen peroxide H 2 O 2 and formaldehyde HCHO have been studied, along with organic molecules such as carbon black that are linked to vegetation emissions and forest fires.
Some of the deposited chemical species may interact with the ice, so what is detected in an ice core is not necessarily what was originally deposited. Another complication is that in areas with low accumulation rates, deposition from fog can increase the concentration in the snow, sometimes to the point where the atmospheric concentration could be overestimated by a factor of two.
Galactic cosmic rays produce 10 Be in the atmosphere at a rate that depends on the solar magnetic field. The strength of the field is related to the intensity of solar radiationso the level of 10 Be in the atmosphere is a proxy for climate. Accelerator mass spectrometry can detect the low levels of 10 Be in ice cores, about 10, atoms in a gram of ice, and these can be used to provide long-term records of solar activity.