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5 major reservoirs 5 major reservoirs: atmosphere, terrestrial biosphere, oceans (and ocean critters), sediments, earth’s interior Short term cycle (days->years) Residence time=(Storage)/(Flux) Long term cycle (millions of years) Earth’s long term climate history: Is any of this due to the long-term, geologic CO2 cycle? Can mountains change the global climate? More recent (Pleistocene, Holocene) Climate • in last 1.8 million years (Pleistocene) repeated glacial cycles. Glacial Consequences • Sea level – Ice ages cause sea level to rise and fall. – Sea level was ~ 100 m lower during the most recent Ice age – If ice sheets melted, coastal regions would be flooded. Causes of Glaciation (Climate Change) • Long-term causes (millions of years) – Set the stage for ice ages. – Plate tectonics – Controls factors that influence glaciation. • Distribution of continents toward high latitudes. • Sea-level flux by mid-ocean-ridge volume changes. • Oceanic currents. – Atmospheric chemistry. • Changes in greenhouse gas concentrations. – Carbon dioxide (CO2). – Methane (CH4). Long-Term Climate Change What causes long-term climate changes? Volcanic gases trap heat, promote global warming. Mid-Cretaceous rifting and expanded mid-ocean ridges. Orogenic uplift consumes CO2 in rock weathering. Leads to overall climatic cooling. Uplift of the Himalayas attended Cenozoic cooling. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 19: Global Change in the Earth System Causes of Climate Change • Short-term causes (10’s to 100’s ka) – Govern advances and retreats. – Milankovitch Cycles changes in Earth’s orbit Causes of Climate Change Milankovitch cycles – Climate variation over 10’s to 100’s Ka predicted by cyclic changes in orbital geometry. • These variations lead to excess warming or cooling. • Ice ages result when cooling effects coincide. Causes of Climate Change • Short-term causes, con’t – Govern advances and retreats. – Changes in albedo (reflectivity). – Volcanic Activity – Sunspot activity – Oceanic thermohaline circulation changes. – atmospheric CO2 concentrations. Global Climate Change Methods of Study. Paleoclimates – Investigations of past climatic variation. Computer simulations – Modeling past and future changes. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 19: Global Change in the Earth System Global Climate Change Paleoclimates – Past climates are indicated by datable Earth materials that are climate sensitive. Stratigraphic records – Sequences of rock strata. Depositional environments are often climate-sensitive. Coral reefs – Tropical marine. Glacial tills – Cold and continental. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 19: Global Change in the Earth System Global Climate Change Paleoclimatic evidence: Paleontological – Faunal assemblages reflect climate. Assemblage changes record climatic shifts. Pollen in pond sediments. o Spruce (colder) vs. hemlock (warmer). o Trees (colder, drier) vs. grasses (warmer, wetter). Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 19: Global Change in the Earth System Global Climate Change Paleoclimates: Oxygen isotopes – Two isotopes: 16O and 18O. 16O water evaporates faster than 18O water. During ice ages… 16O in seawater evaporates faster. This water is trapped on land as ice. Seas become 16O depleted, 18O enriched. 18O/16O increases in remaining seawater. Shells grown in this sea will reflect the altered 18O/16O ratio. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 19: Global Change in the Earth System Global Climate Change Paleoclimates: 16O water evaporates faster than 18O water. During interglacials… Melting ice returns water to oceans. 16O returns to oceans. 18O/16O decreases. Reflected in shells. 400 Ka of 18O/16O data are archived in polar-region ice cores. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 19: Global Change in the Earth System Global Climate Change Paleoclimates: Oxygen isotope ratios are preserved in carbonate shells. The oxygen in CaCO3 shells mirrors oceanic 18O/16O. Sea floor sediments preserve ocean chemistry changes. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 19: Global Change in the Earth System Global Climate Change Paleoclimates: Growth rings – Tree rings can easily be dated. Ring thickness reflects climatic changes. Wetter, warmer = thicker; drier, colder = thinner. Ring widths form time sequences. Overlapping sequences yield a time scale. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 19: Global Change in the Earth System 1. Overview of Climate What Causes the Climate to Vary? Plate Tectonics Volcanic Activity Sun Humans Anthropogenic Changes Global warming – Human GHG additions alter climate. CO2 in the atmosphere has steadily climbed since 1958. In 1958, CO2 was ~ 315 ppm; in 2000, CO2 was ~ 370 ppm. Human additions of CO2 and CH4 outstrip natural removals. Fossil fuel combustion (CO2). Rice-paddy decay (CH4). Cow flatulence (CH4). Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 19: Global Change in the Earth System Th & Friday Dr. Susan Kaspari (climate scientist) Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 19: Global Change in the Earth System Exam #6 Thursday, 8:00 am This Room Will cover and readings and lectures on: Groundwater Glaciers Earth System/Climate Change Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 19: Global Change in the Earth System Glacial Sediment Transport Glaciers carry sediment of all sizes – lots of it! Some sediment falls onto the ice from adjacent cliffs. Some sediment is entrained from erosion of the substrate. When glacial ice melts, this material is dropped. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 19: Global Change in the Earth System Sediment Transport on Ice Moraines – Unsorted debris dumped by a glacier. Lateral – Forms along the flank of a valley glacier. Medial – Mid-ice moraine from merging lateral moraines. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 19: Global Change in the Earth System Depositional Landforms End moraines form at the stable toe of a glacier. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 19: Global Change in the Earth System