Lectures Notes for Exam #3 - Climate Change | GEOG 1113, Study notes of Geography

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CLIMATIC CHANGE ** climate is dynamic, it doesn't stay the same ** there are daily & monthly & annual averages, SO ** climate change is a significant change in these averages over tens or hundreds of thousands of years ** climate system; the interaction of all spheres (atmosphere, lithosphere, biosphere, hydrosphere) * when change occurs in one sphere, it affects the other spheres ** climates have changed in the past at various times & scales, so will probably continue to change *** Evidence of climate change: Seafloor sediments, Oxygen isotope analysis, Tree rings, Palynology, Geology, Historical Records sea floor sediments: change in marine life due to changing climate; the relative abundance of warm/cold water species, or morphological variations in a particular species resulting from environmental factors/change oxygen isotope analysis: the ratio of 18O to 16O in calcareous marine microfauna & from ice cores can indicate glacial vs. inter-glacial periods * this ratio depends on the ocean water T° * 18O doesn’t evaporate out of the seawater as easily as 16O under colder water conditions, thus more 18O will be left in ocean water & thus more will combine with CaCO3 when it recrystallizes to form shell material * SO, when T°s are colder the ratio: in ice core is more 16 than 180. thaw under warmer conditions and in seashells is more 18-0 than 16-0 in warmer conditions tree rings: indicates dry vs. wet periods * wider rings usually indicate wetter periods & narrower rings drier palynology (study of fossil pollens): study of fossil pollens, indicate wet vs. dry and cool vs. warm periods by type of plant pollen; certain species may only exist in warm weather, others in cold (tropical plants vs. spruce or fir of sub polar region. ***Example: pollen of spruce species now only found in Canada are found in soil records in Georgia from period of last Ice Age. *** geologic formations: certain formations will only form under certain climatic conditions, for example coal deposits result from areas of thick vegetation, usually rainforest human historical records: anecdotes & observations written down by people about abnormal weather patterns, like a warmer or colder winter than normal * can only go back for relatively for short period of time *contients move even slower than climates cahnge (after period) ** Other Indications and/or Causes of Climate Chnage: Changes in ability of oceans to store CO2, & heat Changes in ocean currents: directions and/or temperatures, Changes in average sea level: change amount of CO2 & heat stored Changes in levels of photosynthesis activity: affect CO2 levels Changes in storage of carbon in soils: affect CO2 levels Changes in cloud cover: change temps at the Earth’s surface *** Climate change theories: * Non-human Induced Causes: Plate tectonics: land area may "move" into a different climate; could "trigger" a local glacial period, or inter-glacial period some 35° C warmer than it would be otherwise. -- with H2O & CO2 without them 15°C (59°F) -20°C (-4°F) * global warming is basically an enhanced natural greenhouse effect or what I like to call, the greenhouse effect on ‘overload’ Does Global Warming Exist? * last 20-30 yrs: increased levels of CO2, methane & other Greenhouse gases * since 1800 have seen a 25% increase in CO2 levels; highest it has been in past 420,000 years by some estimates * 5 of 6 hottest years on record in 1980's & ‘90's; 2 hottest in 1998 & 2001 * a .6°C T° (1.1° F) increase has been detected since 1861 * predictions that mean surface T°will increase 1.4-5.8° C (2.5-10.4° F) between 2000 & 2100, if trend continues * some melting of land-based ice caps & floating ice around Greenland, Earth’s poles, & shrinking of mountain glaciers Causes for these changes: natural climate fluctuations, Change due to human activities, A combination of both factors Effects of Global Warming: * increased surface temperatures * increased T in polar regions leads to increased melting of ice caps & sea ice * can lead to increased sea levels * alter precipitation patterns such that some areas see an increase, while other areas see a decrease * increase rate of desertification & thus decrease arable land, shifting areas where crops can be grown * affect availability of water resources by altering rates of evaporation & precipitation * alter structure & location of world’s biomes * uncertainties: positive & negative feedback mechanisms * increased T°may lead to increased ice melt, which leads to > water vapor amounts in atmosphere, which leads to increased cloud cover, which leads to decreased solar radiation, which can lead to decreased T° Solutions to Global Warming: * waste less energy by improving efficiency * use less oil & coal * rely more on cleaner energy sources: wind, natural gas, solar, etc Possible economic advantages to following the above: * boost global economy, provide jobs, cost less than trying to deal with the effects of not changing Options: * do nothing: some believe it is not a threat, or even a hoax * do more research before acting * act now to reduce the risks: a type of precautionary strategy, before it gets any worst, or we(humans) are beyond some type of “point of no return” * act now as part of a no-regrets strategy: even if global warming isn’t as bad as some believe, there are other advantages to ‘cleaning-up’ the atmosphere GLACIAL PROCESSES & LANDSCAPES ** Glaciation: glacier: a large body of ice, formed on land from the accumulation and recrystallization of snow, that is in motion * How are glaciers formed? * snow accumulates in zone of accumulation or snowfield; * firn line or snow line, above which firn (granular, compacted snow) develops * through further compaction & recrystallization the firn becomes glacial ice * zone of ablation: a glacier's lower end or area of loss * So a balance is maintained between loss & gain; gain > loss = glacier enlargement, advancing gain < loss = shrinkage (recede) * How do glaciers move? * in response to weight & pressure (gravity) * T° important: colder ice T° = slower movement * internal layers more fluid thus move faster * create cracks in top layers = crevasses * speeds vary from 2-3 cm/day to 4-5 m/day ** Glacial erosion: 2 main processes Plucking: blocks or fragments of the bedrock are pulled from the surface by the ice and carried along * a roche moutonnée may develop: a mound or hump in the surface where plucking occurs primarily on the leeward side of the mound Abrasion: scraping of the surface by rock debris in the ice * varies with the hardness of debris, the rock surface, & speed of glacier * may create glacial polish or smoothing of the surface * OR create striations or scratches in the rock parallel to the direction of movement *** 2 Types of glaciers: ** Continental or ice sheets: over 3000 m(9800 ft) thick; may cause isostatic depression of over 2000 m EX: Greenland & Antarctica * ice cap: continuous ice mass in mts area, circular in shape & less than 50,000 km2; buries underlying landscape; EX: Iceland * ice field: elongated pattern which doesn't cover high peaks & ridges; EX: Patagonian ice field in Andes Alpine or mountain * > 100,000 individual alpine glaciers, found on all continents * largest is the Beardmore Glacier in Antarctica, 125 mi long & 65 mi wide Degradational features: Glacial valleys: have a characteristic U shpae, also caleed galcial trough, straighter than stream formed valleys Hanging valley: a side or tributary valley, evidence of a tributary glacier, usually at a higher elevation than the main valley Fjord: a glacial valley which intersects with the ocean and as been flooded by seawater Mountain landforms Cirque: a scooped out basin at the head of an alpine glacier Arête: a sharp ridge that divides 2 cirque basins Col: a pass or saddle-like depression along an arête Horn: a pyramidal peak caused by several cirque glaciers gouging a mount on all sides Tarn: a small lake which forms collects in a cirque basin behind the lip or edge of the cirque ** Aggradational features: Rock flour: finely ground material or till; this, along with other fine material in the outwash plain, is the "parent material" for löess Lateral moraine: moraines on the edges of the ice mass Medial moraine: moraine running down middle of a glacier, often formed when a trunk(main) & tributary glacier join PERIGLACIAL LANDSCAPES * non glacial processes and landforms associated with cold climates particularly with various aspects of frozen ground * often found in high-latitude or -altitude environments near the perimeter of glaciated areas, or formerly glaciated areas * found today in high polar & subpolar latitudes, BUT during recent periods of glaciation, periglacial activity was found much further south, including GA *** often delineated by those areas which exhibit permafrost, perennially or permanently frozen ground; rock, soil, water (ground ice) etc is always frozen. (<0 degrees Celcius) * 2 conditions for permafrost : 1) T° in the material has remained below 0°C continuously for more than 2 years 2) If pore water is present in the material a sufficiently high percentage is frozen to cement the mineral organic particles * if these conditions are not met, and the ground is frozen, it may be seasonally frozen ground * an active layer may lie directly up on the upper surface of the permafrost (the permafrost table0 and annually freeze andthaw * the depth of the permafrost table will vary from about 15 cm to 5 m below the surface ( 6 in to 20 ft) * it will vary because of ambient air T°, escape of geothermal heat, moisture content of ground, lack of protection of the groound from cover of vegetation, water, or snow, & other factors ** 3 permafrost zones are recognized: * continuous permafrost: thick unbroken expanse of permafrost or near the surface; only unfrozen areas lie beneath lakes, rivers, or the sea * discontinuous permafrost: thinner and contains unfrozen gaps or taliks (unfrozen soil surrounded by permafrost) * sporadic permafrost: small islands of permafrost occur in a generally unfrozen area, sometimes as relics of a former colder climate * continuous or discontinuous permafrost underlies some 20% of the Earth's surface; ~50% of Russia & Canada, 80% of Alaska, & almost all of Greenland & Antarctica *** Periglacial Processes ** frost action: the result of water expanding as it freezes ** frost heave or upfreezing: upward displacement of rock and fragments within actice layer by freezing thawing of ground. may produce patterned ground, also displaces any objects on the surface, such as houses roads, etc. ** frost thrusting: horizontal movement of rock and fragments within the active layer ** frost sorting: process by which migrating particles are sorted into uniform particle sizes by freezing and thawing *** Periglacial Mass Movements ** solifluction: process of slow down slope flow of saturated unconsolidated material; common in sub polar regions with frozen ground or permafrost * may create solifluction lobes, large (100'-150' wide) tongue-like masses of material moving down slope * rates of flow are seasonal & proportional to degree of saturation; may vary from 1 to 10 cm per week or per melt season ** frost creep: down slop movement of particles resulting from frost heaving of the ground normal to the slope and subsequent nearly vertical settling up on thawing. * rates of movement are variable due to the number of freeze-thaw cycles, slope angle, moisture content, etc. ** rock glaciers: large, lobate masses of rock debris frozen in interstitial ice; in some cases may be more like a 'true' glacier with large amounts of rock debris riding atop them ** block field: relatively level areas covered with moderate-to-large blocks of rock produced by frost weding/frost action; also called felsenmeer; if the accumulation is on a slope the feature is called a block slope weathered material * wind can move particles along in 3 ways: Suspension: finest, smallest particles held aloft by wind; will settle-out when the wind slows or stops Dust storm: wind storm in which the finer suspended particles are carried long distances up to thousands of miles, may reach hundreds of feet in the air Sand storm: windstorm in which the larger sand sized particles are carried along in suspension reaches heights of no more than about 2 m off the ground Saltation: larger particles moved along by bouncing them across the surface; up to 80% of materials transported in the formation of dunes is by saltation Surface creep: larger fragments pushed by strong winds and/or saltating particles hitting them ** Eolian Deposition: * various features are created when the wind slows & the transported materials settle out * the most recognizable feature is the sand dune * but only about 10% of desert areas are covered by sand * Depositional Features: Ripples: smallest features shaped by saltating sand grains * form at right angles to the wind direction * look similar to the longitudinal ripples on water Erg: or erg desert, or sand sea; extensive areas of sand dunes * may cover upwards of 75,000 mi2 Dunes: or sand dunes; a wind sculptured accumulation of sand * 3 aspects of dunes to consider: 1) are they stable or unstable(moving) 2) what is their shape or form 3) arrangement in the landscape * anatomy of a dune: windward or stoss side: long gentle slope slipface: leeward side, formed once sand accumulates over 12 inches deep, steeper shorter slope; its angle of repose is 30 to 34 degrees. * dunes may be active or freedunes, which move across the landscape, OR fixed or tied dunes, stabilized by vegetation, higher moisture, rocks, 3 simplified classes of dunes: Crescentric dunes: general crescent shape from unidirectional wind pattern; most common type dune Barchan: a steep slip face that is concave in the downwind direction; the horns of the crescent point in the direction the wind is going Parabolic: the slip face is convex downwind; the horns of the crescent point in the direction the wind is coming from Transverse: elongate dunes that form perpendicular to the prevailing wind direction Barchanoid ridges: similar to transverse dunes, but have a little more curve to them; composed of coalescing barchan dunes Linear dunes: form long parallel ridgest serparted by bare ground, usually in areas of more limited sand supply * are longer than they are wide, formed by converging, bidirectional winds, so the dunes are parallel to the prevailing wind direction * some of the largest measure 185 mi long & 650' high Longitudinal: long slightly sinuous ridge shaped dune with 2 slipfaces Seif: more sinuous crest and shorter than longitudinal dune Star dunes: pin-wheel shape, formed by a complicated, changing wind pattern, often by wind blowing in 3 or more directions * exhibit multiple slipfaces Löess: a deposit of very fine silt and clay material blown by wind sometimes hundreds of miles, often associated with glacial activity * löess in Europe & N. America derived from glacial outwash produced about 15,000 YBP; up to 200 ft thick in the Mississippi & Missouri River valleys, & Great Plains area * löess in China may have resulted from wind-blown desert sediments; Covers over 115,000 mi2, up to 1000 ft thick * develops into very thick, fertile soils Cross-bedding: stratification inclined to the original horizontal surface upon which the sediment accumulated * the pattern seen in some sedimentary rock formations that indicates the material for the rock was former sand dunes ** ARID LANDSCAPES & LANDFORMS * characterized by dry conditions, with little rainfall or vegetation * desert = area which receives < 10 in of rain/year * semi-arid = area which receives 10 - 20 in of rain/year * cover 25-35% of earth's land surface * high potential evapotranspiration (PET) * high insolation (solar input) * distributed at about 20° - 30° N & S latitude; as rainshadows; or far from water sources * landscapes shaped by fluvial & eolian agents, chemical & mechanical weathering ** Fluvial features of deserts: Dry streambeds: only carry water during times of rainfall or flood; also called arroyo, wadi, wash