what chemical is analyzed in ice cores to determine temperature?
When archaeologists want to learn about the history of an ancient culture, they dig deeply into the soil, searching for tools and artifacts to consummate the story. Scientists who study World's past climates, called paleoclimatologists, take a similar arroyo. However, instead of digging into the soil, they expect for clues near our planet'southward climate history by studying coral reefs, digging into ocean and lake floor sediment and drilling deeply into glaciers and ice sheets. The samples they collect from the ice, chosen ice cores, hold a record of what our planet was like hundreds of thousands of years agone.
But where do ice cores come from, and what do they tell the states about climate change? Climate scientist Allegra LeGrande of the NASA Goddard Institute for Space Studies (GISS) and physical scientist Kimberly Casey of the U.S. Geological Survey and Cryospheric Sciences Lab at NASA's Goddard Space Flying Center helped answer these questions and more.
Where do ice cores come from?
Ice sheets and glaciers near World's Due north and Due south Poles formed from years and years of accumulating snowfall. The weight of each year'due south snow compresses down the previous layers of snow, and after many years, all of this pressure helps to form glacial ice. In some areas, these layers result in ice sheets that are several miles (several kilometers) thick.
Researchers drill water ice cores from deep (sometimes more than a mile, or more than than one.6 kilometers) inside the polar ice sheets in Greenland and Antarctica, equally well as some high-breadth ice caps and mountain glaciers. They collect ice cores in many locations around World to report regional climate variability and compare and differentiate that variability from global climate signals.
The samples they collect from the water ice, called water ice cores, hold a record of what our planet was like hundreds of thousands of years ago.
What can the ice tell us nigh past climates?
Each layer of ice tells a story almost what Globe was like when that layer of snow cruel. For example, LeGrande says, as snow deposits onto a growing glacier, the temperature of the air imprints onto the h2o molecules.
The icy layers also hold particles—aerosols such as grit, ash, pollen, trace elements and sea salts—that were in the temper at that fourth dimension. These particles remain in the ice thousands of years later, providing physical evidence of past global events, such as major volcanic eruptions.
Additionally, every bit the ice compacts over time, tiny bubbles of the temper—including greenhouse gases like carbon dioxide and marsh gas—printing inside the water ice. These air pocket "fossils" provide samples of what the atmosphere was like when that layer of ice formed, LeGrande said. "Scientists can directly measure out the amount of greenhouse gases that were in the atmosphere at that time by sampling these bubbling," she added.
How do ice cores aid make predictions about future climate change?
Scientists besides use ice core temperature data to validate climate models that predict Globe'southward future climate. A climate model is like a laboratory inside a computer, LeGrande said. Scientists build all of the existing knowledge about how the atmosphere, ocean, state and ice piece of work into this special laboratory.
They as well have to add in whatsoever variables that may alter the climate organisation at different points in fourth dimension—such as Earth's location in its orbit and how far it will be from the Lord's day.
"Climate models are designed to reproduce the relatively stable climate that people accept observed for the past 160 to 170 years," LeGrande said. "It sounds like a long time, but this used to be possible—in the days of the Farmer's Almanac—because Globe's climate system was quite stable."
However, predicting the climate of the hereafter is a fleck more complicated these days, she said. "The climate of the next century volition be well beyond the range of the climate that we have observed for the terminal 160 years," LeGrande explained.
To test the climate models nether these very dissimilar environmental conditions, scientists test the models by simulating by climates. Ice core records are an essential role of creating and checking these simulations.
How old is the oldest water ice core—and how do nosotros know it'south that old?
The oldest ice cores, from East Antarctica, provide an 800,000-year-erstwhile record of Earth'due south climate. How practice we know they're that old? Each flavour's snowfall has slightly dissimilar properties than the concluding. These differences create almanac layers in the ice that can exist used to count the historic period of the ice, just like rings inside a tree.
"The climate of the adjacent century will exist well beyond the range of the climate that we accept observed for the terminal 160 years."
All the same, the more the ice compacts and the less that snowfall accumulates, the harder it is to see these annual layers. To clarify the age of the deepest layers, scientists utilize a variety of methods, including measurements of the chemic limerick and electrical electrical conductivity of the ice. Scientists also utilize computer modeling techniques that can assist to understand the relationship between the depth of the core and the age of the ice.
How do yous store an ice core?
Subsequently drilling, measuring and logging an ice core, researchers store the cores in bags or netting in cylindrical tubes. Then they pack the tubes into cardboard boxes or protective waterproof hard cases and transport the cores by sled, plane, gunkhole and truck to storage facilities.
Once the ice cores reach storage facilities, scientists digitally record the ice cores' characteristics—such as the presence of volcanic ash or the appearance of bubbles in the ice—in a controlled cold laboratory. The U.S. National Ice Core Laboratory, in Lakewood, Colorado, is the U.S. storage facility, which archives ice cores from all over the globe.
This storage facility as well acts as a library: when scientists desire to study a certain ice cadre from a particular region, they can employ to have a portion of the ice core sent to them for their studies.
How do NASA scientists work with ice cores?
NASA satellites and airborne missions collect data about snow and ice properties, including the snow'south layering, or stratigraphy, and aggregating patterns. This knowledge of the stratigraphy and other properties can be an asset when analyzing the hundreds of thousands of years of snowfall recorded in ice cores.
"In addition to satellite and airborne information collection and analysis, NASA scientists participate in field piece of work to collect ice cores and other related information, such every bit ground penetrating radar," Casey said. "A combination of the ice cadre information with radar and other observational data aids in our understanding of snowfall accumulation, ice flow and climate changes over time."
For the South Pole Ice Core project, in which scientists drilled a core from 2014 to 2016 and proceed the inquiry today, Casey and her NASA colleagues helped clarify satellite, airborne and field information to select a identify to drill the water ice cadre. Ice sheets are enormous, and the scientists had to choose one specific spot that would be both scientifically interesting and near the resources and logistical support they demand for drilling.
The NASA researchers are at present assessing that South Pole ice core to better understand how regional and global climate, atmospheric composition and other variables have changed over the by 40,000 years.
Source: https://climate.nasa.gov/news/2616/core-questions-an-introduction-to-ice-cores/
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