Methods for short term climate reconstruction Flashcards
What do the tools for short term climate analysis mainly consist of?
The tools for short-term climate analysis consist mainly of radiocarbon dating and the analysis of growth rings of trees, speleothems, and corals.
How can scientists use carbon isotope ratio of dead plant material to find about about short term climate models?
scientists can use the carbon isotope ratio of dead plant material to determine past vegetation assemblages and their associated rainfall and temperature conditions.
What is the difference between stable and unstable isotopes?
Up to this point, we have discussed “stable” isotopes of oxygen and carbon, in which protons and neutrons remain together in an atom’s nucleus. However, certain isotopes are “unstable” because the number of neutrons compared to protons is large enough to cause the isotope to decay, or break down, into a different element.
What is a Radioactive isotope?
Radioactive isotope (11) An unstable isotope that decays, or breaks down, into a different element, emitting radiation in the process. The unstable isotope carbon-14 has a constant rate of decay known as a half-life that can be used to date plant material in a technique called radiocarbon dating.
What can Lake cores tell us? and what are Varves?
The sediments at the bottom of glacial lakes provide a record of climate change extending back as far as 50 000 years. Annual layers of lake sediments, called varves, contain pollen, charcoal, and fossils that can be dated using carbon isotopes.
Materials in the layers reflect variations in rainfall, rates of sediment accumulation, and algal growth, all of which can be used as a proxy for climate.
What is Dendroclimatology?
Dendroclimatology
The study of past climates using tree rings. The dating of tree rings by analysis and comparison of ring widths and colouration is dendrochronology.
How can we use tree rings to inform us about past climate conditions?
The width of the growth ring indicates the climatic conditions: Wider rings suggest favourable growth conditions, and narrower rings suggest harsher conditions or stress to the tree (often related to moisture or temperature)
What are speleothems?
Within caves and caverns are calcium carbonate (CaCO3) mineral deposits called speleothems that take thousands of years to form.
A calcium carbonate mineral deposit in a cave or cavern, such as a stalactite or stalagmite, that forms as water drips or seeps from rock and subsequently evaporates, leaving behind a residue of calcium carbonate that builds up over time.
How can speleothems be used to collect data about past climate
Like trees, speleothems have growth rings whose size and properties reflect the environmental conditions present when they formed, and that can be dated using uranium isotopes. These growth rings also contain isotopes of oxygen and carbon, whose ratios indicate temperature and the amount of rainfall.
What are corals
Like the shelled marine organisms found in ocean sediment cores, corals are marine invertebrates with a body called a polyp that extracts calcium carbonate from seawater and then excretes it to form a calcium carbonate exoskeleton.
How can we collect data from corals about past climate conditions?
X-rays of core samples extracted from coral reefs reveal seasonal growth bands similar to those of trees, yielding information as to the water chemistry at the time the exoskeletons were formed (Figure 11.14). Climatic data covering hundreds of years can be obtained this way.
What and when was earths most recent period of repeated glaciations
The Pleistocene Epoch, Earth’s most recent period of repeated glaciations, began 2.5 million years ago.
When was the last glacial period?
The last glacial period lasted from about 110 000 years ago to about 11 700 years ago, with the last glacial maximum (LGM), the time when ice extent in the last glacial period was greatest, occurring about 20 000 years ago.
What was the Younger Dryas?
About 14 000 years ago, average temperatures abruptly increased for several thousand years, and then dropped again during the colder period known as the Younger Dryas. The abrupt warming about 11 700 years ago marked the end of the Pleistocene Epoch.
What is the Medieval Climate Anomaly?
From A.D. 800 to 1200, a number of climate proxies (tree rings, corals, and ice cores) show a mild climatic episode, now known as the Medieval Climate Anomaly (a period during which the Vikings settled Iceland and coastal areas of Greenland). During this time, warmer temperatures—as warm or warmer than today—occurred in some regions, whereas cooling occurred in other regions. The warmth over the North Atlantic region allowed a variety of crops to grow at higher latitudes in Europe, shifting settlement patterns northward.
