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 CO 2 cycle?

Can mountains change the global climate?

More recent (Pleistocene, Holocene) Climate in last 1.8 million years (Pleistocene) repeated glacial cycles. 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 – 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. 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. Distribution of continents toward high latitudes. Sea-level flux by mid-ocean-ridge volume changes. Sea-level flux by mid-ocean-ridge volume changes. Oceanic currents. Oceanic currents. – Atmospheric chemistry. Changes in greenhouse Changes in greenhouse gas concentrations. – Carbon dioxide (CO 2 ). – Methane (CH 4 ).

Essentials of Geology, 3 rd edition, by Stephen Marshak Chapter 19: Global Change in the Earth System 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 CO 2 in rock weathering.  Leads to overall climatic cooling.  Uplift of the Himalayas attended Cenozoic cooling.

Causes of Climate Change Short-term causes (10’s to 100’s ka) – Govern advances and retreats. 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. 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. These variations lead to excess warming or cooling. Ice ages result when cooling effects coincide. Ice ages result when cooling effects coincide.

Causes of Climate Change Short-term causes, con’t – Govern advances and retreats. Short-term causes, con’t – Govern advances and retreats. – Changes in albedo (reflectivity). – Volcanic Activity – Sunspot activity – Oceanic thermohaline circulation changes. – atmospheric CO 2 concentrations.

Essentials of Geology, 3 rd edition, by Stephen Marshak Chapter 19: Global Change in the Earth System Global Climate Change  Methods of Study.  Paleoclimates – Investigations of past climatic variation.  Computer simulations – Modeling past and future changes.

Essentials of Geology, 3 rd 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, 3 rd 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, 3 rd edition, by Stephen Marshak Chapter 19: Global Change in the Earth System Global Climate Change  Paleoclimates:  Oxygen isotopes – Two isotopes: 16 O and 18 O.  16 O water evaporates faster than 18 O water. During ice ages…  16 O in seawater evaporates faster.  This water is trapped on land as ice.  Seas become 16 O depleted, 18 O enriched.  18 O/ 16 O increases in remaining seawater.  Shells grown in this sea will reflect the altered 18 O/ 16 O ratio.

Essentials of Geology, 3 rd edition, by Stephen Marshak Chapter 19: Global Change in the Earth System Global Climate Change  Paleoclimates:  16 O water evaporates faster than 18 O water. During interglacials…  Melting ice returns water to oceans.  16 O returns to oceans.  18 O/ 16 O decreases.  Reflected in shells.  400 Ka of 18 O/ 16 O data are archived in polar-region ice cores.

Essentials of Geology, 3 rd 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 CaCO 3 shells mirrors oceanic 18 O/ 16 O.  Sea floor sediments preserve ocean chemistry changes.

Essentials of Geology, 3 rd 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.

Humans 1. Overview of Climate What Causes the Climate to Vary? Plate Tectonics Volcanic Activity Sun

Essentials of Geology, 3 rd edition, by Stephen Marshak Chapter 19: Global Change in the Earth System Anthropogenic Changes  Global warming – Human GHG additions alter climate.  CO 2 in the atmosphere has steadily climbed since  In 1958, CO 2 was ~ 315 ppm; in 2000, CO 2 was ~ 370 ppm.  Human additions of CO 2 and CH 4 outstrip natural removals.  Fossil fuel combustion (CO 2 ).  Rice-paddy decay (CH 4 ).  Cow flatulence (CH 4 ).

Essentials of Geology, 3 rd edition, by Stephen Marshak Chapter 19: Global Change in the Earth System Th & Friday Dr. Susan Kaspari (climate scientist)

Essentials of Geology, 3 rd 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, 3 rd 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, 3 rd 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, 3 rd edition, by Stephen Marshak Chapter 19: Global Change in the Earth System Depositional Landforms  End moraines form at the stable toe of a glacier.