An Arctic Perspective on 20th Century Warming
Dr. Gifford Miller, INSTAAR and Geological Sciences, University of Colorado, Boulder
Abstract: As the planet has warmed over the past century, Arctic temperatures have increased at 2 to 3 times the global rate, with documented reductions in sea ice, glacier size, and snowcover, reflecting the strong positive feedbacks operating in the polar regions. However, the extent to which recent Arctic warming has been anomalous with respect to long-term natural climate variability remains uncertain. We use radiocarbon measurements on rooted tundra plants exposed by recent ice-cap retreat to provide a millennial perspective on summer temperature change. Over 300 14C dates on plants entombed beneath ice in Arctic Canada demonstrate that 5000 years of regional summertime cooling has been reversed, with 100-year average summer temperatures now higher than during any century in more than 45,000 years, including peak warmth of the early Holocene when solar energy in summer was 9% greater than present. Our results suggest that anthropogenic increases in greenhouse gases have led to unprecedented Arctic warmth, with implications for lower latitudes through sea-level rise and changes in Northern Hemisphere atmospheric circulation.
Biography: Gifford Miller is Professor of Geological Sciences and Fellow of the Institute of Arctic and Alpine Research (INSTAAR) at the University of Colorado, Boulder, where he also serves as Associate Director. His research focuses on utilizing the record of the recent geological past, primarily in hot and cold deserts, to gain a better understanding of Earth’s climate system, and the role of humans in the Earth System. He has long-standing research programs in the Eastern Canadian Arctic, Australia, Iceland, and Svalbard.
Giff focuses primarily on the Late Quaternary, with a goal of gaining a better understanding of Earth’s climate system. His early research was dominantly in the cold deserts of the Polar Regions, with current field projects in the Eastern Canadian Arctic, Svalbard, Iceland and West Greenland, where his research group focuses on abrupt climate change and placing current summer warming in a millennial perspective. In mid-career Miller became interested in hot deserts and monsoon systems while working in North Africa. He has focused on the Australian Summer Monsoon, causes of megafaunal extinction and the footprints of human colonization in Australia for the past 25 years. Recently, his research group expanded the megafuanal extinction work to Madagascar, where he is evaluating the extinction of the Elephant Bird, Aepyornis.
Landscape Evolution of Colorado
Late Neogene Tectonic and Volcanic Fragmentation and Middle Pleistocene Climate-Driven Drainage Integration of the Southern Rocky Mountains
Cal Ruleman, Geology and Environmental Change, USGS
Synopsis: The southern Rocky Mountains have long been a focus for lithologic, structural, and geomorphic studies. Building on this previous work using newly developed geomorphic, chronologic, geodetic, geophysical, and pedologic analyses, I am developing a unified model to: (1) explain the timing and mechanism for regional middle Pleistocene incision; (2) determine regional correlations; and, (3) resolve discrepancies between bedrock and surficial geologists. I will highlight recent work on diamictons and Quaternary deposits in the San Luis Valley, Sawatch Range, and upper Arkansas valley. Through this work I have developed the following geomorphic sequence: (1) deposition of extensive Rocky Flats-correlative alluvium on adjacent Rocky Mountain piedmonts and continued tectonically-induced aggradation within Rio Grande rift basins (>640 ka); (2) eruption of the Lava Creek B tephra at ~640 ka; (3) subtle landscape dissection and deposition of inset Verdos-correlative alluvium (~621-478 ka); (4) San Luis basin spillover and integration into Rio Grande and widespread deposition of diamicton on Poncha Pass and around the perimeter of high altitude mountains (478-374 ka); and, (5) intermountain deep-canyon incision and adjacent Front Range and San Juan Basin piedmont incision and widespread deposition of Slocum-correlative alluvium on flanking piedmonts (~374-191 ka). All younger deposits and landforms are deeply inset into the topography and easily distinguishable.
Full Abstract:The southern Rocky Mountains have long been a focus for lithologic, structural, and geomorphic studies. Building on this previous work using newly developed geomorphic, chronologic, geodetic, geophysical, and pedologic analyses, I am developing a unified model to explain the timing and mechanism for regional middle Pleistocene incision, determine regional correlations, and resolve discrepancies between bedrock and surficial geologists. Recent work within the San Luis Valley, Sawatch Range, and upper Arkansas Valley demonstrate a linkage between the Lake Alamosa highstand ~385 ka, maximum basin fill elevation, and deposition of the first Pleistocene diamicton above generally finer-grained deposits of the Santa Fe Group and Dry Union Formation. These boulder diamictons have been previously mapped around the region as QTd or Tg (Quaternary-Tertiary diamicton or Tertiary gravel) depending on the breadth of geologic time the author was familiar with and focusing on. They were also generally interpreted to be the result of rapid tectonic uplift. The presence of ~640 ka Lava Creek B ash in the underlying, lower-energy deposits of the Santa Fe Group provides a maximum age for the diamicton and indicates a <640ka dramatic change in the basin-fill sedimentology leading to deposition of coarse axial gravels linking previously closed, and disconnected intermountain basins adjacent to the high elevations. We interpret these sedimentologic and geomorphic relationships to indicate the regional onset of major middle Pleistocene glacial episodes younger than MIS 16, ~676-621 ka. Within the San Luis Valley, maximum aggradation elevation, basin integration processes, and incision into the Rio Grande gorge occurred even later, <420 ka (MIS 12), coeval to placement of the first diamicton on Poncha Pass. Poncha Pass is where intermountain tectonically-fragmented basin stratigraphy meets the Front Range piedmont Pleistocene stratigraphy along the Arkansas River and through the Royal Gorge. Regional geologic mapping and topographic correlations demonstrate that similar relationships (i.e., coarse bouldery deposits with a silty clay matrix capping interfluves and overlying/pre-dating deeply incised topography) exist in the Aspen region and across South Park, along the Black Canyon of the Gunnison and Eagle River, and potentially adjacent to any region above 3600 m (~12,000 feet).
The geomorphic sequence is as follows: 1) deposition of extensive Rocky Flats-correlative alluvium on adjacent Rocky Mountain piedmonts and continued tectonically-induced aggradation within Rio Grande rift basins (>640 ka)(>MIS 16); 2) eruption of the Lava Creek B tephra from the Yellowstone caldera complex ~640 ka; 3) subtle landscape dissection and deposition of inset Verdos-correlative alluvium containing Lava Creek B ash on piedmonts (i.e., Front Range/Denver , San Juan, Wind River, and Bighorn Basins)(~MIS 15-13, ~621-478 ka; 4) San Luis basin spillover and integration into Rio Grande and widespread deposition of diamicton on Poncha Pass and around the perimeter of high altitude mountains (MIS 12-11, 478-374 ka); 5) intermountain deep-canyon incision and adjacent Front Range and San Juan Basin piedmont incision and widespread deposition of Slocum-correlative alluvium on flanking piedmonts (MIS 11-7, ~374-191 ka). All younger deposits and landforms are deeply inset into the topography and easily distinguishable. Coeval to glacially-induced middle Pleistocene Southern Rockies incision, Great Plains neotectonics and the evolution of the Arkansas River-Sand Creek-South Platte fluvial system can be directly related to the timing of Laurentide “Kansan” glaciation, the southernmost and most expansive Laurentide icesheet during the Pleistocene. Tentative correlations suggest that Front Range Bear and Clear Creek drainages have the same geomorphic sequence, explaining peculiar deposits and geomorphic relations between Green and North and South Table Mountains and the Continental Divide.
Biography:Cal Ruleman studied geology at the University of Montana and Montana State University and has been performing geological investigations for the last twenty years in various tectonic and geomorphic settings including Montana, Idaho, Wyoming, Nevada, Colorado, New Mexico, Alaska, Suriname, South America, Afghanistan, and Nepal. He joined the U.S. Geological Survey in 2007. His work has ranged from Archean to Holocene with a focus on geomorphology and landscape evolution. In addition to geologic mapping, paleoseismology, and geomorphic analyses, he employs various Quaternary relative and absolute dating techniques including pedology, 3He-, 10Be-, and 26Al-surface exposure dating, and U-Th soil carbonate dating techniques to resolve geologic problems. His geologic mapping and investigations within the Rocky Mountains from western Montana to northern New Mexico address: 1) temporal and spatial migration of intermountain neotectonics, 2) the timing and process of gorge formation and deep incision below glaciated regions, 3) timing of Last Glacial Maximum ~22 ka and rates of deglaciation, 4) timing of onset and sequence of major Pleistocene glaciations of North America, and 5) bedrock structural development of the region over multiple tectonic episodes. Building upon the lithologic, structural, and geomorphic findings of our predecessors, he combines newly developed geomorphic, chronologic, geodetic, paleoseismologic, geophysical, and pedologic analyses to develop unified models explaining the timing and mechanism for regional middle Pleistocene incision, quantifying geomorphic processes, determining regional correlations, and attempting to resolve discrepancies between traditional bedrock and surficial geologists.
The Far-Reaching Effects of Wastewater Injection: Recent Case Studies of Anthropogenic Earthquakes
Will Yeck, National Earthquake Information Center, USGS
Abstract: Anthropogenic earthquakes, primarily the result of deep fluid injection, currently contribute significantly to the overall earthquake hazard in the Central and Eastern United States. While the majority of these induced earthquakes currently occur in Oklahoma, Colorado has a long record of injection induced earthquake sequences that form the basis of our broader understanding of the phenomenon. The connection between fluid injection and seismicity was first observed in the early 1960’s when a series of damaging earthquakes near Denver occurred due to the injection of waste fluids at the Rocky Mountain Arsenal. In response to these earthquakes, the USGS led an induced seismicity experiment in the late 1960’s in Rangely, Colorado, that confirmed the hypothesis that seismicity correlates with increased fluid pressure. Since 1991, the Bureau of Reclamation has been monitoring induced earthquakes associated with fluid injection at Paradox Valley and has observed earthquakes up to ~20 km from the causative well. Elsewhere in Colorado, wastewater injection has increased the rate of earthquakes in the Raton Basin since 2001, including a damaging M 5.3 earthquake in 2011. Most recently, a 2014 M 3.2 earthquake was induced by wastewater injection near Greeley, Colorado, and rapid mitigation efforts were employed to prevent continuing seismicity.
The lessons learned from the case examples of Colorado-induced earthquakes give insight into the wide-scale induced seismicity in Oklahoma. Since the early 2000s, the rate of earthquakes in Oklahoma has increased dramatically, including the occurrence of significant and damaging events. Since 2011, Oklahoma has experienced four moderate sized (M5-6) earthquakes, three of which occurred in 2016. In contrast, only two moderate sized events, in 1882 and 1952, are historically documented. Combining observations from induced earthquakes in Colorado and Oklahoma, we now have a large dataset to evaluate the effectiveness of commonly employed mitigation strategies. Key observations from moderate sized earthquakes in Oklahoma include: (1) the existence or extent of causative fault is often unknown prior to an earthquake’s occurrence, (2) induced earthquakes often occur with little to no foreshock activity, and (3) moderate sized earthquakes can occur at large distances (>15 km) from high-rate injection wells. The combination of these observations demonstrates the difficulties in mitigating associated earthquake hazards. In 2015, Oklahoma began regional mitigation strategies aimed at reducing the volume of injected fluid. The rate of earthquakes decreased in 2016 compared to 2015, which suggests that reducing volumes can reduce the earthquake rate. Still, 2016 hosted three moderate sized events and therefore had a substantially larger cumulative moment release as compared to previous years. The combination of detailed real-time monitoring, detailed source characterization research, and evaluation of yearly hazard estimates will continue to improve our understanding of the hazard presented by induced events.
Speaker Biography: William Yeck is a research geophysicist with the U.S. Geological Survey National Earthquake Information Center, located at the Geologic Hazards Science Center in Golden, Colorado. His research focuses on improved real-time detection and characterization of earthquake sources, anthropogenic seismicity within the United States, and better spatio-temporal characterization of damaging earthquake sequences for long-term hazard assessment. Will received his B.S. in Physics at the University of Wisconsin – Madison and a Ph.D. in Geophysics at the University of Colorado at Boulder. His Ph.D. research primarily addressed issues of crust and upper mantle structure and the associated kinematic evolution of the Rockies during the Laramide orogeny. During his Ph.D., Will worked at the U.S. Bureau of Reclamation studying earthquakes induced by fluid injection at Paradox Valley, Colorado.
Simple, Serious, and Solvable: The Three S’s of Climate Change
Scott Denning, Atmospheric Sciences, Colorado State University
Thursday, April 20, 2017
Synopsis: Simple, Serious, and Solvable: The Three S’s of Climate Change
Climate Change is Simple. Heat in minus heat out equals change of heat. When Earth absorbs more heat than it emits, the climate warms. There is no doubt that adding CO2 reduces Earth’s heat emission and therefore causes global warming.
Climate Change is Serious. In addition to more drought, a warmer climate will include heavier rainfall during extreme events. Warmer ice sheets release more water the oceans, which also expand as they get warmer. These two influences raise sea levels, threatening coastlines everywhere. Without strong policy, these impacts will become more and more severe, almost without bound.
Climate Change is Solvable. Preventing catastrophic climate change will require abundant and affordable energy to be made available to people everywhere without emitting any CO2 to the atmosphere. This will require both the development of energy efficient infrastructure and very rapid deployment of non-fossil fuel energy systems, especially in the developing world.
Abstract: Simple, Serious, and Solvable: The Three S’s of Climate Change
Climate Change is Simple. Heat in minus heat out equals change of heat. When Earth absorbs more heat than it emits, the climate warms. When it emits more than it absorbs, the climate cools. This simple principal explains why day is warmer than night, summer is warmer than winter, and Miami is warmer than Minneapolis. It also explains why adding CO2 to the air causes global warming. The absorption of thermal infrared radiation by CO2 was first measured 150 years ago, has since been confirmed thousands of times by labs all over the world, and is extremely well understood. There is no doubt at all that adding CO2 reduces Earth’s heat emission and therefore causes global warming.
Climate Change is Serious. Warmer average temperatures are associated with dramatic increases in the frequency of extremely hot weather. Warmer air evaporates more water from soils and vegetation, so even if precipitation doesn’t change the demand for water will increase with warmer temperatures. Adding water vapor to the air also means there is more water available for heavy rains when the right conditions occur: this means that in addition to more drought, a warmer climate will include heavier rainfall during extreme events. Warmer ice sheets release more water the oceans, which also expand as they get warmer. These two influences raise sea levels, threatening coastlines everywhere. Higher seas imply much more frequent coastal flooding, requiring abandonment long before mean sea level reaches coastal infrastructure. Without strong policy, these impacts will become more and more severe almost without bound, growing to become the most serious problems in the world and lasting for many centuries after fossil fuels are abandoned. The consequences of unchecked climate change to the global economy are unacceptable.
Climate Change is Solvable. Preventing catastrophic climate change will require abundant and affordable energy to be made available to people everywhere without emitting any CO2 to the atmosphere. This will require both the development of energy efficient infrastructure and very rapid deployment of non-fossil fuel energy systems, especially in the developing world. From an engineering perspective, both objectives are eminently feasible with mature technologies. Economically, the clean energy transition will be expensive, involving roughly 1% of the global economy. This cost is comparable to previous development achievements such as indoor plumbing, rural electrification, the global internet, and mobile telecommunications. Our descendants will better lives by developing and improving their infrastructure just as our ancestors did.
Speaker Biography: Professor Scott Denning received his B.A. in Geological Sciences from the University of Maine in 1984, and his M.S. and Ph.D. degrees in Atmospheric Science from Colorado State University in 1993 and 1994. He studied radiometric geochronology, surface water geochemistry, and mountain hydrology before becoming interested in global climate and biogeochemical dynamics. After a two-year postdoctoral appointment modeling global sources and sinks of atmospheric CO2, he spent two years as an Assistant Professor in the Donald Bren School of Environmental Science and Management at the University of California at Santa Barbara. He joined the Atmospheric Science faculty at Colorado State University in 1998, and has served as Director of Education for the Center for Multiscale Modeling of Atmospheric Processes (CMMAP) since 2006. He does a lot of outreach about climate change, and takes special delight in engaging hostile audiences.