Marine Science fall 2004 01/11:L628:200

Liz Sikes (office: 103 E) extension 932-6555 ext 518

Lecture outline September 28.

Reading Sverdrup et al., 2004 pp 83-85 (history of the continents) pp 33-36 (geologic time)

I. Climate Signals

A. Temperature

B. Oxygen isotopes as a recorder of climate

Case study: the ¹⁸O record

Fractionation occurs as a distillation. ¹⁸O records temperature and ice volume

II. Tectonic toˆ orbital control on climate

A. Tectonic control

Circum-equatorial versus circumpolar circulation controls overall climate

Cretaceous has circum-equatorial circulation that warms the globe.

Eocene to Oligocene gyres shift equatorward and circum-polar circulation begins.

The Antarctic continent is isolated by opening of Drake passage and glaciers begin to build up

Mid Miocene is when the deep circulation is circumpolar

Pliocene- Pleistocene closing the isthmus of Panama at about 3.0 Ma. Basins are set like present

- beginning of Northern hemisphere glaciation 2.5Ma.

B. Glacial (orbital) mode of climate cycling.

The beginning of glacial pulsing occurs after north-south circulation is set

Orbital forcing is driven by net changes in insolation

Feedbacks (e.g. greenhouse gases) can amplify the effect

Summary and concepts to know

Chemical proxies in the geological record can be used to interpret past climate.

Oxygen isotopes record temperature.

Climate History: Moving from a "green house" world to an "ice house" world.

Climate is controlled by plate tectonics over millions of years (long term)

The locations of continents controls currents and heat transport on the earth and so controls climate.

The second control on climate is: Orbital forcing

Orbital parameters control climate on time over thousands of years (shorter term).