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).

Essentials of Geology, 3rd 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 CO2 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. – 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.


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.


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).


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.



16O water evaporates faster than18O 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.



Oxygen isotope ratios are preserved in carbonate shells.The oxygen in CaCO3 shells mirrors

oceanic 18O/16O.Sea floor sediments preserve ocean

chemistry changes.



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 ClimateWhat Causes the Climate to Vary?

Plate Tectonics

Volcanic Activity

Sun


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).


Th & FridayDr. Susan Kaspari (climate scientist)


Exam #6 Thursday, 8:00 am This Room Will cover and readings and lectures on:

Groundwater Glaciers Earth System/Climate Change


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.


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.


Depositional Landforms

End moraines form at the stable toe of a glacier.

5 major reservoirs

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