Ch 12- Earth’s Changing Climate – Flashcards
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10%
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Glaciers cover less than ___% of the earth's land surface
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Greenland and Antarctic
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Most of this ice is in the ______ ; _____ ice sheets, and its accumulation over time has allowed scientists to measure past climatic changes
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-Inundated (Flooding) -Rise in Global T (:. rise sea levels)
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2 Catastrophic results of ice melting?
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advancing and retreating
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The study of geological evidence left behind by _____ ; _____ glaciers is one factor suggesting that global climate has undergone slow but continuous changes
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Samples from ocean floor sediments and ice from Greenland and Antarctica (CLIMAP)
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What is another form of evidence of global climatic changes?
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Climate: long-range investigation mapping and prediction...observed the ocean floor and remains of Cá2+ carbonate shells of organisms (their life indicates the T of surface water)...and Ó2-isotopes
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What is CLIMAP?
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When ocean water evaporates, the heavy Ó2-18 tends to be left behind... :. during glacier advancement, the oceans have less water ; have more Ó2-18
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How does the Ó2-isotope ratio of those organisms' shells tell us about the sequence of glacier advances?
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Yes, a higher ratio of 18:16 in the sediment suggests a colder climate, whereas a lower ratio = warmer climate
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Does comparing the ratio of Ó2-18 to Ó2-16 give info about climate change in past?
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Yes, by examining the Ó2-isotope ratio in ancient cores provides a past record of T trends...the colder the air when the snow fell, the richer the [Ó2-16] in core
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Do vertical ice cores extracted from ice sheets in Antarctica and Greenland provide additional info on past T patterns?
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Yes, by 1. deducing from layers of sulfuric acid in the ice (how much came from volcanoes/humans) 2. Checked for chemicals that provide records of biological and physical changes in the climate system, such as Be that indicates solar activity
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Do ice cores record the CAUSE of climate change? (2)
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Study of annual growth rings of trees to see climate change
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What is Dendrochronology?
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As the tree grows, it produces a layer of wood cells under its barks...each year's growth appears as a ring,,,the change in thickness of rings indicates climatic changes
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How does dendrochronology work?
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1. Records of natural lake-bottom sediment and soil deposits 2. Study of pollen in deep ice caves, soil deposits, and sea sediments 3. Certain geological evidence and the change in the water level of closed basin lakes 4. Documents concerning droughts, floods, crop yields, rain, snow, and dates of lakes freezing and trees blossoming 5. Study of Ó2-isotope ratio fo corals 6. Dating Cá2+-carbonate layers of stalactites in caves 7. Borehole T profiles, which can be inverted to give records of past T change at the surface 8. Deuterium (heavy H), ratios in ice cores, which indicate T changes
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Other data used to reconstruct past climate changes:
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Warmer B/c the polar regions were free of ice
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Throughout much of the earth's history, the global climate was probably much ______ than it is today?
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ICE AGE- one glacial period occurred about 700 million years ago and another about 300 million yrs ago
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What caused T's to be colder?
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Pleistocene epoch
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What is the most recent Ice Age?
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Polar ice appeared when cold era occurred....then Ts dropped and ice grew thicker...snow and ice began to accumulate in high mountains of N. Hem., and alpine glaciers soon appeared -2.5 Ma, glaciers appeared in N. Hem, marking the beginning of the Pleistocene epoch
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How did Pleistocene Epoch appear?
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NO...it was a time when glaciers alternatively advanced and retreated (melted back) over large portions of NA and Europe
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Was the Pleistocene a period of continuous glaciation?
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Interglacial periods...btw glacial advances, it was a warmer period
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What caused the glaciers to melt/warmer period was called?
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1900-45: increased 1945-70: decreased 1990+: increased
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Describe the current T change from 1900-45, 45-70, ; 1990+?
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Yes, but also increasing about 2C/century...significant compared to history
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Is the current global warming continuing?
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-
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*The earth's climate is constantly undergoing change. Evidence suggests that throughout much of the earth's history, the earth's climate was much WARMER than it is today*
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*The most recent glacial period (Ice Age) began about 2.5 Ma. During this time, glacial advances were interrupted by warmer periods called interglacial periods. In NA, continental glaciers reached their max thickness and extent about 18,000-22,000 Ya and disappeared completed from NA about 6,000 Ya*
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*The Younger Dryas event represents a time about 12,000 Ya when northeastern NA and Northern Europe reverted back to glacier conditions*
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*During the 20th century, the earth's surface T increased by about 0.6C. This global warming has NOT only continued, but over the last several decades has increased*
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Changes in: 1. Incoming solar radiation 2. Composition of atmosphere 3. Earth's surface
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3 External causes of climate change?
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-all 3 -2/3
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Natural phenomena cause cause climate to change by which of the 3 mechanisms? Human actions?
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Yes, such as changes in the circulation patterns of the ocean and the atm, which redistribute E within the climate system, rather than altering the total amount of E it holds
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Are there also internal causes of climate change? (i.e.)
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T rises, and water from oceans evaporates into air...the increased quantity of water vapor absorbs more of the earth's IR energy
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Explain how a warming trend increases the greenhouse effect?
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T's even more, which allows for more water vapor to evaporate...etc. etc.
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What does the increased greenhouse effect raise? (Water vapor-Greenhouse feedback)
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(+) b/c the initial increase in T (stimulus) is reinforced by other stuff
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Is the water vapor greenhouse feedback a (+/-) feedback?
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another (+) feedback case, in which an increase in global surface air T might cause snow and ice to melt...which reduces the albedo (reflectivity) of the surface, allowing more solar E to reach the surface, which further raises the T
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What is the snow-albedo feedback?
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those that tend to weaken the interactions among the variables rather than reinforce them
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What are (-) feedback mechanisms?
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-Chemical weathering-CÓ2 feedback: ...as chemical weathering increases, the amt of CÓ2 in atm. decreases ...as Ts dip, less water evaporates from oceans, chemical weathing decreases, and the removal of CÓ2 from atm Dimishes
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Ex of one
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ya
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Point being: earth-atmosphere has a number of checks and balances called feedback mechanisms that help it counteract tendencies of climate change
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Theory of plate tectonics
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So, we see that one of the causes of climate change is the change in the surface of the earth....what is the theory where the slow shifting of the continents and the ocean floors called?
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According to this theory, the earth's outer shell is composed of huge plates that fit together like pieces of a jigsaw puzzle...the plates, which slide over a partially molten zone below them, move in relation to one another. Continents are embedded in the plates and move along like luggage riding piggyback on a conveyor belt...the rate of motion is extremely slow, only a few cm/year
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What is the theory of plate tectonics?
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Its pieces slowly moved across the face of the earth...when landmasses are concentrated in middle ; high latitudes (as of today), ice sheets are more likely to form...greater chance of more sunlight to reflect back into space from the snow...less sunlight absorbed by surface lowers air T, which allows for a greater snow cover, and the formation of continental glaciers
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According to the theory, the now existing continents were at one time joined together in a single huge continent, which broke apart...how does this explain climate change?
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Yep
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Is the theory also related to CÓ2 levels?
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chain of volcanic mountains forming perpendicular to the mean wind flow may disrupt the airflow over them, altering the climate both upwind and downwind...also mountains built on continental plates (Himalayan) can have marked influence on global circulation patterns and on the climate
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How can mountains change climate?
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Milankovitch theory
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Name of theory that describes the climatic changes to variations in the earth's orbit (amount of solar radiation that reaches the earth)
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as the earth travels through space, 3 separate cyclic movements combine to produce variations in the amount of solar energy that falls on the earth
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What is the basis of the theory>? PAPER!!!
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-Eccentricity...shape of the earth's orbit as the earth revolves about the sun -earth's orbit changes from being elliptical to being nearly circular, which alters the amount of sun the earth gets
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1st cycle deals w/ changes in the ______
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Wobbles like a spinning top
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2nd cycle takes into account the fact that, as the earth rotates on its axis, it ______ like a _____
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Precission
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The wobble is know as the ____ of the earth's axis
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1. Changes in the shape (eccentricity) of the earth's orbit about the sun 2.Precession of the earth's axis of rotation, or wobbling 3. changes in the tilt (obliquity) of the earth's axis
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Milankovitch cycles summary:
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No...evidence of air bubbles in glaciers show that lower Có2 levels may have had the effect of amplifying the cooling initiated by the orbital changes -Likewise, increasing Có2 levels at the end of the glacial period may have accounted for the rapid melting of the ice sheets
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Are these orbital changes the only thing responsible for ice buildup and retreat?
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No, b/c something caused a change in Có2 levels, but it may be due to shifts in the oceans circulation patterns
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Are CÓ2 levels changing the primary reason for glacial period?
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1. Amt of dust and other aerosols in atm 2. Reflectivity of the ice sheets 3. [other greenhouse gases] 4. Changing characteristics of clouds 5. Rebounding of land, having been depressed by ice
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List of other factors that work in conjunction with the M. Theory to explain the T variations between glacial and interglacial periods:
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Yes!!! they occur in cycles, with the # and size reaching a maximum about every 11 yrs ...they account for small climatic changes over time scales of decades and centuries
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Do Variation in solar output affect climate change?
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Yes
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Do microscopic and solid particles (aerosols) affect climate?
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wildfires, dust storms, volcanoes, oceans
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What are some natural ways for particles to enter near the surface?
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They cool the surface by preventing sunlight from reaching the surface
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What is the overall effect they have?
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Ash/dust
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During volcanic eruptions, fine ____ & ____ are ejected into the atm
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Sulfur
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Scientists agree that the volcanic eruptions having the greatest impact on climate are those rich in ____ gases?
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Wate vapor + sunlight = haze -Reflection of haze tends to cool the air at the earth's surface, especially in the hemisphere where the eruption occurs
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When sulfur is in the atmosphere, what does it combine with to make haze? Effects of haze?
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That volcanoes played an important role in triggering this comparatively cool period in the past
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In an attempt to correlate sulfure-rich volcanic eruptions with long-term trends in global climate, scientists are measuring the acidity of annual ice layers in Greenland and Antarctica. Generally, the greater the [sulfuric acid] the greater the acidity of the ice layer...what do these finding suggest?
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GIANT CRATER...crashed into earth, and could have sent billions of dust/debris into the upper atm, where they circled the globe and reduced the sunlight to the earth...cutting off photosynthesis, and led to destruction of food chain
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What is the theory for how particles ended up in the upper atmosphere and led to the mass extinction of dinosaurs?
