Short term cycle (days->years) Residence
time=(Storage)/(Flux) Long term cycle (millions of years)
Slide 4
Earths long term climate history: Is any of this due to the
long-term, geologic CO 2 cycle?
Slide 5
Can mountains change the global climate?
Slide 6
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.
Slide 7
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.
Slide 8
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 ).
Slide 9
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.
Slide 10
Causes of Climate Change Short-term causes (10s to 100s ka)
Govern advances and retreats. Short-term causes (10s to 100s ka)
Govern advances and retreats. Milankovitch Cycles changes in Earths
orbit
Slide 11
Causes of Climate Change Milankovitch cycles Climate variation
over 10s to 100s Ka predicted by cyclic changes in orbital
geometry. Milankovitch cycles Climate variation over 10s to 100s 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.
Slide 12
Causes of Climate Change Short-term causes, cont Govern
advances and retreats. Short-term causes, cont Govern advances and
retreats. Changes in albedo (reflectivity). Volcanic Activity
Sunspot activity Oceanic thermohaline circulation changes.
atmospheric CO 2 concentrations.
Slide 13
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.
Slide 14
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.
Slide 15
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).
Slide 16
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.
Slide 17
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.
Slide 18
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.
Slide 19
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.
Slide 20
Humans 1. Overview of Climate What Causes the Climate to Vary?
Plate Tectonics Volcanic Activity Sun
Slide 21
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 1958. 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 ).
Slide 22
Essentials of Geology, 3 rd edition, by Stephen Marshak Chapter
19: Global Change in the Earth System Th & Friday Dr. Susan
Kaspari (climate scientist)
Slide 23
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
Slide 24
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.
Slide 25
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.
Slide 26
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.