2024 Dec 5 Global Change and Earth System PDF

GLGY 376 – Dec 5, 2024 Chapter 19 – Global Change and Earth System “The problem is not to find the answer, it’s to face the answer.” -Terence McKenna  Types of Global Change 1. Rate – Gradual vs. Catastrophic 2. “Trend” – Unidirectional vs. Cyclic/Episodic ...

GLGY 376 – Dec 5, 2024 Chapter 19 – Global Change and Earth System “The problem is not to find the answer, it’s to face the answer.” -Terence McKenna  Types of Global Change 1. Rate – Gradual vs. Catastrophic 2. “Trend” – Unidirectional vs. Cyclic/Episodic  Geology at a Glance The Earth System Life on Earth is due to interaction among the lithosphere, the atmosphere, and the hydrosphere. The “Earth System” is composed of these physical components interacting with the biosphere. Global Change involves transformations among the physical and biological components of Earth Systems through time.  Fig. 2.1b Plate tectonics This modern depiction of Pangaea is based on abundant evidence compiled over the last 30 years augmenting evidence collected by Alfred Wegener.  Earth (4th edition), Fig. 23.4 Physical cycles: the supercontinent cycle Plate tectonics drives a dance of the continents. Ocean basins open and close. Continental land masses collide and rift apart again. Geology repeats itself. Mantle convection (release of heat) Essentials of Geology, 4th Edition Copyright © 2013, W.W. Norton & Company  Fig. 11.2c Formation of continental crust The Archean Eon, the time between By ~3.85 Ga, Earth had cooled to 3.85 and 2.5 Ga, witnessed the birth form lithosphere, intense meteorite of continents and of life on Earth. bombardment ceased, and parts of the rock record begin to survive. The volume of continental crust increased dramatically. (By the end of the Archean, ~85% of modern continental area was present.) This indicates that plate tectonics was in action.  Fig. 18.26a, b Temperature change Oxygen isotopes ratios from marine sediments define 20 to 30 Pleistocene glaciations. Earth history has witnessed many ice ages.  Fig. E.8 Evolution of biosphere The Paleozoic ended with the Permian extinction, which eradicated 90% of all marine species.  Fig. 10.10 Unidirectional changes: the evolution of life Origin of Life Life appeared quickly on Earth, by 3.8 Ga. Living organisms have modified the entire Complex life appears surface of Earth, changing the composition of the atmosphere and altering the chemistry of the oceans. Age of dinosaurs Cambrian Explosion: Shells appear Age of mammals  Fig. E.8 Catastrophic changes Catastrophic events impart changes to Earth very rapidly. Catastrophic changes to the local landscape include volcanic eruptions, earthquakes, and tsunamis. The geologic record bears evidence that catastrophic events happen on a global basis. Catastrophic events are tied to some mass extinctions. The dinosaur mass The Paleozoic ended extinction at the end of with the Permian the Cretaceous is extinction, which attributed to a eradicated 90% of all meteorite impact. marine species.  Chapter 11 opener Atmospheric composition Atmospheric oxygen (O2) skyrocketed between 2.4 and 2.2 Ga as a result of cyanobacteria (blue-green algae). Evidence of oxygen buildup is preserved in banded iron formations (BIFs), which are red because of oxidized iron (Fe). BIFs, which occurred worldwide during this time, are major iron ores today.  Fig. 19.4 Sea-level “cycle” Sea level is geologically unstable; it has gone up and down many times in Earth history. Sedimentary rocks preserve evidence of sea level changes.  Fig. C.1 Rock and hydrologic cycles – steady state One rock type may transform into any other type. Thus, the atoms in rocks are constantly being rearranged. Rock recycling requires long periods of time. Biogeochemical cycles Biogeochemical cycles involve chemical fluxes between living and nonliving matter.  Interlude F, Geology at a Glance Biogeochemical cycles: the hydrologic cycle The hydrologic cycle consists of water in motion between biological (organisms) and physical (oceans, atmosphere, surface water, groundwater, ice caps, glaciers, soils, etc.) reservoirs.  Fig. 19.5 Biogeochemical cycles: the carbon cycle In the carbon cycle, carbon transfers between several near-surface reservoirs, including the ocean, the atmosphere, organisms (living and dead), and rocks.  Global climate change Earth’s climate changes over geologic time scales. Long-term climate change operates on a millions to tens-of- millions-of-years scale. Short-term climate change is on the order of tens to hundreds of thousands of years in scale.  Fig. 19.6 Long-term climate change Geologists have reconstructed an approximate record of global climate for geologic time. Global climate history has oscillated between warmer and colder climates. Warmer climates are called greenhouse periods; colder climates are icehouse periods. Long-term climate change is driven by several factors: - Positions of continents - Uplift of land surfaces - Changes in mantle convection - Life evolution  Fig. 18.26a Natural short-term climate change: the Pleistocene Climate changes lasting centuries to hundreds of thousands of years are considered to be short-term. The climate variability of the Pleistocene, as indicated from fossils, sediments, and isotopes, indicates that continental glaciers have advanced and retreated 20 to 30 times in the Northern hemisphere. Short-term climate changes are regulated by several factors: Fluctuations in solar radiation and cosmic rays Changes in Earth’s orbit and tilt Changes in volcanic emissions Changes in ocean currents Changes in surface albedo Abrupt changes in concentrations of greenhouse gases  Earth (4th edition), Fig. 23.10b Historical archives contain records of floods and Paleoclimates: historical record droughts that can help assemble a climate history.  Fig. 10.14b, c Paleoclimates: growth rings Growth rings in tree rings can easily be dated. The ring thickness reflects climatic changes. Wetter and warmer conditions generate thicker rings. Drier and colder conditions produce thinner rings. The sequence of alternating thick and thin rings forms a time sequence that can be matched with other tree data. Overlapping sequences yield a time scale.  Fig. 19.8a Paleoclimates: ice-cores Bubbles trapped in ice cores preserve the chemical composition of the atmosphere at the time the ice formed. Ice cores contain annual layers that can be readily dated.  Fig. 19.8b, c Paleoclimates: oxygen isotopes Oxygen isotope ratios indicate the temperature of past environments. Two oxygen isotopes are used: 16O, which is lighter, and 18O, which is heavier. 16O water evaporates faster than 18O water. During ice ages, the 16O water evaporated more readily and was trapped on land as glacial ice. Seas then become 16O-depleted and 18O-enriched (the 18O/16O ratio increased). Shells grown in this sea water The oxygen isotope record is preserve the 18O/16O ratio. read from glacial ice (left) and fossil shells in sediment (right).  Fig. 19.9a Natural short-term climate change: the Holocene Little Ice Age The Holocene, comprising the past 15,000 years, starts with the warming that led to deglaciation. Medieval Warm Period Climate has fluctuated across the Holocene. Early Holocene warming was interrupted by a cooling event (Younger Dryas ~10,500 B.C.E.). Holocene Maximum Climate warming reached a peak at 5,000 to 6,000 years ago called the Holocene Maximum. During the Middle Ages, the climate was again Younger Dryas warm (the Medieval Warm Period). A cold period known as the Little Ice Age lasted from 1500 to 1800 C.E. Climate has warmed since 1800 C.E.  Fig. Bx.19.1 Global climate change: the role of greenhouse gases. Most of the incoming visible light from the Sun penetrates the atmosphere and warms Earth’s surface. This absorbed energy is released from the surface as infrared (thermal) energy. Certain gases, including H2O, CO2, CH4, in Earth’s atmosphere absorb thermal energy and reradiate it, warming the lower atmosphere. This is called the greenhouse effect because it operates in a manner similar to the way glass traps heat in a horticultural greenhouse. Global climate change: the role of greenhouse gases Without greenhouse gases, Earth would be a dead, frozen world. Water (H2O) is the most important greenhouse gas (~15 º C), followed by carbon dioxide (CO2). Any process that increases the amount of greenhouse gases warms the atmosphere. Any process that removes greenhouse gases cools the atmosphere.  Fig. 19.13a, b Human impact on the Earth System: recent global warming The graph shows temperature This graph is of the change in global average reconstructions during the past 2,000 temperature since 1880. Both the southern and years. Each color represents the results of northern hemispheres show warming. a study from a different location. Average land & shallow ocean water temperatures (Fig 19.18)  p -from Berkeley Earth  Human Impact on the Earth System Prehistoric humans had a very small impact. Today, however, humans are a powerful force of planetary change, rivaling or exceeding some natural processes. Human impact stems from exponential population growth aided by revolutions in industry, agriculture, technology, and medicine, fueled by accessible natural resources.  Recent Global Warming: Human Greenhouse Gases ▪ Human greenhouse gas emissions have steadily increased since the start of the industrial revolution. CO2 in the atmosphere has steadily climbed since the first direct measurements in 1958. The annual oscillation reflects CO2 removal by plants in the northern-hemisphere summer. In 1958, CO2 was ~315 ppm; in 2010, it had risen to ~390 ppm. Measuring CO2 in glacial ice, researchers have discovered that CO2 in 1750 was only 280 ppm. Saturated water vapour content  Fig. 19.13c Human impact on the Earth System: recent global warming From ice-core studies, CO2 concentration was found to have varied from 180 to 280 ppm throughout glacial advances and retreats. The current value of 415 ppm is beyond the range of natural variation for the last 800,000 years.  4th edition,Fig. 19.15c, 19.16 Human impact on the Earth System: recent global warming Colors represent anomalies (differences relative to the average temperature of the period from 1950 to 1980). Redder areas are warmer; blue areas are cooler. The position of anomalies changes over time. It is interesting to note that not all change is warming, although warming dominates. Measured values of near-surface ocean water temperatures are rising.  Fig. 19.14b, d Human impact on the Earth System: recent global warming Thousands of published observations suggest that, yes, warming has occurred. Arctic summer sea ice coverage has decreased dramatically. Valley glaciers worldwide have been retreating rapidly. The Muir Glacier, Alaska, retreated 12 km between 1941 and 2004. p p  Fig. 19.15a Human impact on the Earth System: recent global warming Below are model calculations of the extent of global warming with variation in the input amount of CO2. Even the low emissions model shows substantial warming.  Fig. 19.15a Human impact on the Earth System: recent global warming Below are model calculations of the extent of global warming with variation in the input amount of CO2 as predicted in 1988.  Fig. 19.15a Human impact on the Earth System: recent global warming Below are model calculations of the extent of global warming with variation in the input amount of CO2 as predicted in 1988.  Fig. 19.15b Human impact on the Earth System: recent global warming Computer models do not predict equal warming everywhere. The greatest impact is predicted to be in the Arctic.  Fig. 19.16c Human impact on the Earth System: recent global warming If global warming continues, sea level will continue to rise. Many people live within a meter of sea level. A sea level rise of 1 or 2 m could inundate portions of the world where 20% of the human population lives.  Sea level changes (left >100m rise since glacial maximum; right current observed trend in cm) p Ocean acidification A chemical model can be constructed based upon: 1.Partial pressure of CO2 2.Observed pH of ocean water 3.Observed carbonate and bicarbonate concentrations in ocean http://www.beachapedia.org/Ocean_Acidification Current forest cover vs. 8,000 years ago "While we live surrounded by unknown unknowns, we live on the basis of unknown knowns - intractable facts that we prefer to forget. We'd do better to confront these awkward realities and muddle through more intelligently. We humans are sturdy and resilient animals, with enormous capacities of creativity and adaptability, but consistently realistic thinking seems to be beyond our powers. This may well be the biggest unknown known of them all - in an age that prides itself on its advancing knowledge and superior understanding, we're as anxious as ever to avoid facing up to our actual condition.." - John Gray (BBC, “A Point of View” http://www.bbc.com/news/magazine-25680144 )  The long term/billions of years Earth atmospheric carbon dioxide concentration trend has been…? A) up B) unchanged C) down D) orders of magnitude downwards E) unknown  Which of the following is a unidirectional global change? A) rock cycle B) cooling of the Earth by mantle convection C) hydrologic cycle D) sea level change E) none of the above  Sea level on Earth is currently rising relative to the continents due to …? A) expansion of water due to global warming B) collision of the Indian plate with Asia C) melting of ice on the continents D) slowing of seafloor spreading E) both A) and C)