FINAL GLG111 Book Notes

Terms in this set (57)

-Extreme climate environments are characterized by exceptionally high or low temperatures, a lack of precipitation, or both.
-On land, a long-lived mass of slow-moving snow and ice is termed a ___; they form where there is a steady supply of snow and cold temperatures year-round.
-Two major types of glaciers:
--___ glaciers, or ice sheets, form on landmasses at polar latitudes; Antarctica and Greenland are examples. These glaciers may last for millions of years.
--In contrast, smaller glaciers, called ___ glaciers, can be found at high altitudes in mountainous regions on every continent except Australia; typically flow down from high ground to fill lower valleys and are more susceptible to climate fluctuations than continental glaciers. They could last for decades to thousands of years, depending on location and size
-As a rule of thumb, the more ice that accumulates in the glacier, the more rapidly it will flow
-__-steep, narrow cracks in the glacier's surface- form as the shape of the glacier changes to conform to the shape of the underlying valley floor.
Small air bubbles are trapped between compacted ice particles and preserved in the ice crystals. These tiny bubbles preserver a record of the composition of the atmosphere at the time of their formation.
-The layers in a glacier represent annual accumulations of snow that were subsequently converted to ice.
-A glacier can be divided into zones based on elevation:
--The higher ____ zone is usually the thickest part of the glacier, where the addition of snow exceeds loss by melting
--The lower, thinner area is the ____ zone ("removal"), where the seasonal snow melts, causing the glacial ice below to thaw
--The boundary between the accumulation and ablation zones of the glacier is indicated by the snow line.
-The mass balance of the glacier is the difference between the amount of snow and ice that accumulates and melts each year.
-If accumulation exceeds ablation, the glacier grows in size and moves downslope.
-If ablation exceeds accumulation, the glacier melts faster than new ice can be added, and the front of the glacier retreats upslope.
-Glaciers are not just ice: they also contain rock fragments from large boulders down to sand- and clay-sized particles.
-The farthest limit of a glacier is marked by a terminal moraine (a ridge at the end of the glacier)
-Glaciers that reach the ocean may break into icebergs or form a shelf of ice that floats in the protected waters of a shallow bay.
-Icebergs and ice shelves carry clay, sand, and larger boulders that were eroded by the glacier. As the ice melts, these sediments drop into the ocean and descend to the ocean floor to form a dropstone deposit.
-Melting glaciers are a key source of water supplies for farmers and cities around the world. As glaciers shrink and recede, water supplies will inevitably decline, and this is arguably the most significant consequence of climate change.
-In most hot deserts, temperatures are high, annual rainfall is less than 25 cm (10 in) and ___ exceeds precipitation.
-Most desert surfaces are a combination of sand, desert pavement, and regions dominated by rock outcrops.
-Occasional flash floods and wind action are responsible for eroding, transporting, and depositing material in deserts.
-Sand grains may be deposited together to form sand dunes.
-Dunes have a pattern of sloping layers, known as cross beds, that slope in the same direction as the wind blows.
16.5 Records of Climate Change
-We term any indicator as a ___ for climate. A ___ is something that stands in for something else.
-The detailed, accurate data on temperature and precipitation that are necessary to characterize climate have only been collected for about 150 years.
-Historical and archeological records indicate that changes in climate patterns influenced where past civilizations were able to flourish (or not).
-Cultural records for the Northern Hemisphere indicate that the last 1,000 years or so can be divided into 3 distinct informal climate periods:
1. European agricultural records and histories of the settlement of Greenland both illustrate that temperatures were relatively warm from A.D. 1000 to around 1450. This period of apparent warmth is known as the "Medieval Warm Period."
2. The next 400 years were marked by some excessively cold periods interspersed with more "normal" temperatures. This period has been labeled the "Little Ice Age", although it was not really an ice age, just a time of relatively cold climate.
3. Finally, toward the end of the 19th century, the climate appears to have moderated, leading to our present relatively warm temperatures, which exceed any experienced during the previous 1,000 years.
-Tree rings, lake sediments, and ice layers yield information about annual changes.
-Dendrochronology (tree ring research) can reveal relatively short-term climate change cycles.
--Tree rings vary in size. The width of the rings can be used to decipher climate history during tree growth; wide rings occur during wet, warm years, narrow rings during cool or dry years.
-Much like tree rings, lake sediments are often deposited in pairs of light and dark annual layers, which can be interpreted to reveal the climate history of their region.
--These paired layers, known as varves, reflect seasonal changes in deposition in the lake.
-Like varves, ice layers can be counted to determine their age. The thickness of the layers is indirectly related to temperature and directly tied to precipitation.
-Oxygen isotopes (oxygen atoms with different numbers of neutrons) serve as a proxy climate indicator for long-term timescles.
-Oxygen isotopes as measure in foraminifera carry at least 2 signals: ice volume and temperature.
-The oxygen isotope ratio acts as a paleothermometer for ancient climates. That is, we can compare the oxygen isotope ratio and foram population proxies with modern values.
-Widespread evidence such as moraines and other glacial features indicates that the Northern Hemisphere experienced glaciation during the last 2 million years. This period of extremely cold climate is termed an ice age.
--See level was lower because much of the water was trapped as ice; consequently, the amount of exposed continent was larger.
--Lower sea levels resulted in a land bridge between Siberia and Alaska
--Eastern North America was forested. Forests extended into present-day grassland regions such as the Great Plains, which experienced higher rainfall.
--Deserts in the western US were cooler, and thus less evaporation occurred there during glacial times. This may have coupled with the increased moisture or the same amount of moisture that the region receives today. In either case, the net effect was greater stream discharge and large regional lakes.
-Analysis of oxygen isotope ratios and other proxies has been used to divide the ice age into 120,000-year-long cycles featuring long cold intervals known as glacials (about 100,000 years) and short warm intervals termed interglacials (about 20,000 years).
-Temperature history is determined from analysis of ice cores from Antarctica. Warmer interglacials occurred at approximate 100,000-year intervals and were separated by colder glacial intervals characterized by significant temperature fluctuations. Glacials were about 5-10 degrees Celsius colder than today, and interglacials could have been a few degrees warmer.
-The average annual temperature of much of the Northern Hemisphere increased by 8 degrees Celsius (12 degrees F) in less than a decade!
-When huge volumes of freshwater are introduced into the ocean, like when ice sheets start to melt, the thermohaline circulation that drives the oceanic conveyer belt is slowed or stopped. Once Earth's oceanic heat engine is disrupted, temperatures plummet.
-Earth was 10 to 15 degrees C (18-27 degrees F) warmer 52 million years ago.
-Dramatic climate changes occurred more than 10,000 years ago because there was a huge accumulation of ice that melted and flooded the northern Atlantic Ocean with freshwater.
-Only some of the increase in global temperature is directly attributable to rising greenhouse gas concentrations. A larger proportion is related to ___ systems that alter Earth's energy balance and exaggerate the warming trend.
-Feedback results when the output of a system affects the input.
-Radiation from the sun is scattered, reflected, or absorbed by Earth. The balance between reflected energy and absorbed energy determines the temperature of Earth.
-Any phenomenon that causes a change in the global solar radiation balance is known as a ___ ___. Forcings are considered positive if they result in global warming and negative if they cause global cooling. A positive factor increases an existing trend; a negative factor causes a trend to slow down or reverse.
-Approximately ___ of incoming solar radiation is reflected back to space. The rest is absorbed by the atmosphere and the land and water of Earth's surface. Infrared radiation from the heated surface is trapped by greenhouse gases in the atmosphere, adding more warmth to the atmosphere. An increase in greenhouse gases added 2 to 3 watts per square meter more warming to the atmosphere.
-Aerosols are an example of a negative forcing. Most aerosols are particles that reflect sunlight back into space, so they cause a negative forcing and diminish the warming effect for some industrialized nations.
-Forcings are only one-half of the story. There are reactions to forcings. The warming or cooling caused by forcings leads to climatic feedbacks that can exaggerate or reduce temperature changes.