Transcript 5 major reservoirs 5 major reservoirs: atmosphere, terrestrial biosphere, oceans (and ocean critters), sediments, earth’s interior.

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
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What causes long-term climate changes?
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Volcanic gases trap heat, promote global warming.
Mid-Cretaceous rifting and expanded mid-ocean ridges.
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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
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Methods of Study.
Paleoclimates – Investigations of past climatic variation.
 Computer simulations – Modeling past and future changes.
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Essentials of Geology, 3rd edition, by Stephen Marshak
Chapter 19: Global Change in the Earth System
Global Climate Change
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Paleoclimates – Past climates are indicated by datable
Earth materials that are climate sensitive.
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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
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Paleoclimatic evidence:
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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
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Paleoclimates:
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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
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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.
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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
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Paleoclimates:
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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
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Paleoclimates:
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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
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Global warming – Human GHG additions alter climate.
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CO2 in the atmosphere has steadily climbed since 1958.
In 1958, CO2 was ~ 315 ppm; in 2000, CO2 was ~ 370 ppm.
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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
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Thursday, 8:00 am
This Room
Will cover and readings and lectures on:
Groundwater
 Glaciers
 Earth System/Climate Change
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Essentials of Geology, 3rd edition, by Stephen Marshak
Chapter 19: Global Change in the Earth System
Glacial Sediment Transport
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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
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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
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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