Ice and Ice Cores

Ice cores, the material Sattler relies upon for much of her research, are an invaluable resource for many different fields of study. While Sattler utilizes the cores to investigate microorganisms and their ecosystems, climatologists use cores to decipher the world's past climatic variations and find clues for what the future climate may hold in store.

CAREFUL, CALCULATED EXTRACTION

Cores are gathered via highly precise drilling mechanisms. While near-surface-layer cores require technical tools to be gathered, samples extracted from depths reaching over 3000m require truly significant technological devices. Cores are usually removed in 2-6m long sections; the short length aims to both ease transportation of the sample to its ultimate spot of analysis as well as to decrease the likelihood of the sample being harmed during extraction. A typical extraction requires a drill bit to be lowered into the sample hole, and when it reaches where it last left off, it begins to drill the next sample. As the blade cuts down, the sample is encased by an inner barrel of the drill. When the drill reaches the end of the core length (2-6m, depending upon the drill), the core is broken off and the sample is hoisted back up to the surface. Importantly, samples extracted from deep below the surface go from an area of high pressure (consider the weight of the entire ice sheet above it) to one of relatively low pressure as they approach the surface. For these samples, scientists have determined that it is essential to allow the cores a chance to "relax" at cooler-than-surface temperatures for up to a year's time. If relaxation time is not permitted, samples will often fracture from expansion and valuable information can be lost. During long ice coring sessions, expedition teams will often establish a natural "relaxation zone" for the cores, comprised of a storage hole dug a little way into the ice. They are thus able to utilize their surrounding environment to cool the cores as opposed to bringing in additional refrigeration units (a difficult and costly option considering the remote nature of many drill sites).

It is imperative that ice cores are meticulously catalogued upon extraction because each core must be ordered properly between the core that preceded it and the one that followed during analysis.  As ice cores layers correspond directly with time, their chronological interpretation is essential to understanding what the data suggests has occurred in the past.

DECIPHERING THE ICE

Each layer of an ice core offers a snapshot into data about that year's (or, for samples dating further back where layers begin to merge under the increased pressure, the data corresponds to a slightly longer time period than years) temperature, ocean volume, precipitation, chemistry and gas composition of the lower atmosphere, volcanic eruptions, solar variability, sea-surface productivity, desert extent, and forest fires. This information is extracted from relative concentrations of wind-blown dust, ash, bubbles of atmospheric gas, and radioactive substances found in the year’s snow layer. The layers stack one atop the next year after year as in the polar regions, snow lasts throughout the seasons. As years accumulate over time, the older layers lower down are increasingly compressed until wafer-thin samples remain. Highly technical analysis is required to be able to infer the above characteristics from the sample data. Temperature, for example, is determined by the concentration of heavier isotopes of water as compared to lighter isotopes. The gas data, on the other hand, is retrieved from air bubbles caught within the core's layers.