Deciphering past climates. Flashcards
What are some of the environments that we can find clues as to what past climates were like?
Clues to past climates are stored in a variety of environments on Earth. Among these climatic indicators are gas bubbles in glacial ice, fossil plankton in ocean-bottom sediments, fossil pollen from ancient plants, growth rings in trees, speleothems (mineral formations in caves), and corals.
How can scientists access the environmental indicators from environmental sources?
Scientists access these environmental indicators by extracting cores from deep within the various materials, which are then analyzed by various methods to determine age and climate-related characteristics. In this way, scientists can establish a chronology of environmental conditions over time periods of thousands or millions of years.
What is Paleoclimatology?
Paleoclimatology
The science that studies the climates, and the causes of variations in climate, of past ages, throughout historic and geologic time.
The study of Earth’s past climates is the science of paleoclimatology, which tells us that Earth’s climate has fluctuated over hundreds of millions of years.
What is a Proxy method?
Proxy method (11) Information about past environments that represents changes in climate, such as isotope analysis or tree ring dating; also called a climate proxy.
A climate proxy is a piece of information from the natural environment that can be used to reconstruct climates that extend back further than our present instrumentation allows.
What is an Ice age?
Climate reconstructions spanning millions of years show that Earth’s climate has cycled between periods that were colder and warmer than today. An extended period of cold (not a single brief cold spell), in some cases lasting several million years, is known as an ice age, or glacial age. An ice age is a time of generally cold climate that includes one or more glacials (glacial periods, characterised by glacial advance) interrupted by brief warm periods known as interglacials.
What is Isotope Analysis
Isotope analysis (11) A technique for long-term climatic reconstruction that uses the atomic structure of chemical elements, specifically the relative amounts of their isotopes, to identify the chemical composition of past oceans and ice masses.
Using this knowledge, scientists can reconstruct temperature conditions.
What is “light” oxygen and “heavy oxygen”?
An oxygen atom contains 8 protons, but may have 8, 9, or 10 neutrons. The atomic weight of oxygen, which is approximately equal to the number of protons and neutrons combined, may therefore vary from 16 atomic mass units (“light” oxygen) to 18 (“heavy” oxygen).
What are the different properties of H2O that contain 16 O and 18 O
If the water contains “light” oxygen (16O), it evaporates more easily but condenses less easily. The opposite is true for water containing “heavy” oxygen (18O), which evaporates less easily, but condenses more easily.
Why dose the atmosphere have more 16 O? Why dose it get trapped in the slow around the poles?
Since 16O evaporates more easily, over time the atmosphere becomes relatively rich in “light” oxygen. As this water vapour moves toward the poles, enrichment with 16O continues, and eventually this water vapour condenses and falls to the ground as snow, accumulating in glaciers and ice sheets
Why is the ocean more enriched with 18 O
the oceans become relatively rich in 18O—partly as a result of 16O evaporating at a greater rate and partly from 18O condensing and precipitating at a greater rate once it enters the atmosphere.
When is “light” oxygen usually locked in the snow and when dose it typically return to the ocean to create more of a balance?
During periods of colder temperatures, when “light” oxygen is locked up in snow and ice in the polar regions, “heavy” oxygen concentrations are highest in the oceans (Figure 11.7a). During warmer periods, when snow and ice melt returns 16O to the oceans, the concentration of 18O in the oceans becomes relatively less—the isotope ratio is essentially in balance
What are foraminifera?
Oxygen isotopes are found not only in water molecules but also in calcium carbonate (CaCO3), the primary component of the exoskeletons, or shells, of marine microorganisms called foraminifera.
What are Ice cores.
In the cold regions of the world, snow accumulates seasonally in layers, and in regions where snow is permanent on the landscape, these layers of snow eventually form glacial ice (Figure 11.9a). Scientists have extracted cores of such glacial ice to reconstruct climate.
Where can the worlds largest accumulations of glacial ice be found?
The world’s largest accumulations of glacial ice occur in Greenland and Antarctica.
What dose a lower 18-O/16-O ratio in Ice cores suggest?
In ice cores, a lower 18O/16O ratio (less “heavy” oxygen in the ice) suggests colder climates, where more 18O is tied up in the oceans and more light oxygen is locked into glaciers and ice sheets.
