Climate Record on Ice Core
The record could help us keep the old memories that we don’t want to forget. Also, record the huge amount of data that we can’t memorize inside our head but we need to read it anytime. It may be through the phone in your own hand, satellites record imagery or any other instruments.
Like other recorders nowadays, the earth also has its own nature recorder. That record has been memorized every single event on the earth since the planet was young and all the time. That record could tell us the story about the earth climate begins with its childhood memories.
The earth keeps a detailed diary written in the snow yesteryears. Climate scientists read it by drill ice core from the depth of the glacier in Greenland and Antarctica. The ice layer has the ancient air trapped inside them. We can read the record of climate and atmosphere back at the last 800.000 years.
How can ice store those kinds of information?
Greenhouse gasses
The most important property of ice cores is that they are a direct archive and recorder of past atmospheric gasses. Air is trapped at the base of firn layer, and when the compacted snow turns to ice, the air is trapped in bubbles. The ice encloses small bubbles of air that contain a sample of the atmosphere is possible to measure directly the past concentration of gases (including carbon dioxide and methane) in the atmosphere. The air bubbles are extracted by melting, crushing or grating the ice in a vacuum.
Direct and continuous measurements of carbon dioxide (CO2) in the atmosphere extend back only to the 1950s. Ice core measurements allow us to extend this way back into the past. This method provides detailed records of carbon dioxide, methane and nitrous oxide going back over 650,000 years. (British Antarctic Survey, Antartic Glaciers)
Antarctic ice cores show us that the concentration of CO2 was stable over the last millennium until the early 19th century. It then started to rise, and its concentration is now nearly 40% higher than it was before the industrial revolution. It was confirmed that the increase due to emissions of CO2 from fossil fuel usage and deforestation. Methane (CH4), another important greenhouse gas, also shows a huge increase over the last two centuries. This is mainly due to the increase in emissions from sources such as rice fields, ruminant animals and landfills, that comes on top of natural emissions from wetlands and other sources.
Past air temperature
Unfortunately it can be explained by chemistry by the way. So, water is made up of molecules of H2O, two hydrogen atoms bonded to an oxygen atom.
Not all hydrogen and oxygen is alike. For example, some oxygen is made up of sixteen subatomic particles, which we might call oxygen-16, and some oxygen is made up of eighteen subatomic particles, oxygen-18. Chemically, they behave the same. They bond with hydrogen and make water. But physically, oxygen-16 is lighter than oxygen-18. These two types of water then are known respectively as light water and heavy water.
Imagine we’re in a cold climate. The ocean is made up of both of these types of water. It has heavy water in it, and light water in it. When the sun shines on the ocean, energy from the sunlight transforms some of this water into water vapor, and so it enters the atmosphere. Which do you think is easier to evaporate, a molecule of light water or a molecule of heavy water?
The light water. It’s lighter, you need less energy to lift it up. So if the climate is cool, more light water will enter the atmosphere than heavy water, compared to when climate is warmer. The heavier something is, the more energy you need to move it. So this means in cool periods, the clouds produced from this evaporation have more light water than we normally expect. So when precipitation falls out of these clouds in a cold climate, then at Antarctica, it falls as snow, we see that snow is enriched in light water. In other words, it has more Oxygen-16 in it than Oxygen-18.
When climate gets warmer, there’s more energy available to evaporate the water molecules. This means that it’s easier to pick up those heavy water molecules, those water molecules that contain eighteen oxygen atoms in them. So, the water that enters the atmosphere and gets turned into cloud, and then falls as snow, has a different composition of heavy versus light water than during the cold periods.
Now, let’s consider, how does an ice sheet get build up over time? At first, the climate is cool. And so, in this case there is less heavy water than usual. Perhaps the climate next. It’s gets warmer. This means we have a greater per portion of heavy water than we did before. And perhaps then, we return back to our cold state, and so now again, the snow falling has less heavy water. What’s interesting is that different levels of ice in that ice sheet have different isotopic compositions.
Now, if we drill a core of this size and extract it, we can measure the fraction of heavy to light isotopes. And figure out whether or not the climate in the past, when that snow was laid down to form that ice, was from a warm period or a cold period. In other words, we can use these measurements to determine what the temperature of the ocean was that produced the snow that created the ice.
The climate has varied much in the past, and there is a clear correlation between the amount of carbon dioxide in the atmosphere and the temperature. As the level of carbon dioxide goes up, we see higher temperatures.
In the past, global temperature change varied in a range of about -0.2 deg Celcius to 0.4 deg Celcius on average, depending on the amount of CO2 in the atmosphere caused mostly by volcano activities. The ice core record that all. Since the industrial revolution in 1800, the climate is changing for the first time in Earth’s history because of non-natural factors. The waste gasses, mostly CO2, pump by industries to the atmosphere up to 30 billion ton/year while volcanoes pump maximal at 500 million ton/years of CO2, it does not even reach 2% than caused by industries activities, burning fossil. The huge amount of CO2 in the atmosphere then joins with other greenhouse gasses until the level which leads to global warming. Since the industrial revolution, the global temperature change keeps rise and reach about 1.2 deg Celcius nowadays.
[1] https://www.bas.ac.uk/data/our-data/publication/ice-cores-and-climate-change/
[2] http://scienceindia.in/home/view_blog/106
[3] http://www.dynamicscience.com.au/tester/solutions1/chemistry/greenhouse/paleoanswers.html
[4] http://www.antarcticglaciers.org/glaciers-and-climate/ice-cores/ice-core-basics/
[5] https://www.bas.ac.uk/data/our-data/publication/ice-cores-and-climate-change/
