A Look into the Past Ice Cores By Felicia McDonald

What is an ice core?  Accumulation of snow and ice over many years that have re-crystallized and have trapped air bubbles from previous time periods. The composition of these ice cores, especially the presence of hydrogen and oxygen isotopes, provides a picture of the climate at the time.

How do we get ice cores? Teams of scientist are sent out to remote ice sheets. They set up drills that cut through the ice pulling up cylinders of ice. Each core is measured and packed for transport to the National Ice Core Laboratory. ( NICL)

Who studies ice cores? Paleoclimatology is the study of past climate, for times prior to instrumental weather measurements. Paleoclimatologists use information from natural climate "proxies," such as tree rings, ice cores, corals, and ocean and lake sediments, that record variations in past climate.

What do Paleoclimatologists find? Ice core records show temperature, precipitation, chemistry and gas composition of the lower atmosphere, volcanic eruptions, and other factors that affect climate.

Findings There are air pockets throughout the cores that have information about the atmosphere and temperature at the time. Isotopes and greenhouse gas concentrations found in these pockets help determine climate information. –Higher concentrations of light oxygen show colder temperatures. –Deuterium also shows temperature. If there is a large amount this is an indication of warmer temperatures. (BBC News)

Findings Scientists measure the temperature of an ice sheet directly by lowering a thermometer into the borehole that was drilled to retrieve the ice core. Like an insulated thermos, snow and ice preserve the temperature of each successive layer of snow, which reflects general atmospheric temperatures when the layer accumulated. Close to the surface of the bedrock, the lowest layers of the ice are warmed by the heat of the Earth. These physical temperature measurements help calibrate the temperature record scientists obtain from oxygen isotopes. (Graph based on data provided by Gary Clow, United States Geological Survey) Then these records are compared with the analysis or the ice core itself.

Findings As far as greenhouse gases these studies are still in progress. CO 2 is a big part of warming but scientist are still researching its affects. This research will help determine the what effect global warming is having on climate.

Greenland Study

Analysis of Ice Cores Ice cores can be analyzed by gas chromatography. Gas Chromatography is chromatography in which the substance to be separated into its components is diffused along with a carrier gas through a liquid or solid adsorbent for differential adsorption.

Dating an Ice Core 1.Counting Annual Layers 2.Counting with the use of a Reference horizon. 3.Radioactive Dating of Gaseous Inclusions 4.Ice Flow Calculation l

Why is this information important? The record found in ice cores allow us to compare the trends of the 20 th and 21 st centuries to far back into the past. With this knowledge we can determine the Earth’s natural variability. In understanding the roles of natural variability we can decipher climate change due to nature versus human- induced climate change. Knowing the difference we can create models that can simulate weather and help us predict future climate.

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