Notes

Outline

Earth System Climate (ESS200A)

Course Description A general description of the Earth climate system and  its subcomponents: the atmosphere, ocean, land surface, ice, and solid earth.

Course Outline: Climate System

Syllabus Week 1-2: Atmosphere  (Chapters 3 and 4) Global Energy Cycle Basic Structure and Dynamics General Circulation in the Troposphere General Circulation in the Stratosphere Week 3: Ocean (Chapter 5) Basic Structure and Dynamics Surface Ocean Circulation: Wind-Driven Deep Ocean Circulation: Density-Driven Week 4: land surface and Cryosphere  (Handout) Land Surface Properties (Soil and Vegetation) Surface Energy and Water Balance Sea Ice and Land Ice Climate Roles of Land Surface and Ice

ATMOSPHERE (Outline)  Global Energy Balance  Basic Dynamics  General Circulation in the Troposphere  General Circulation in the Stratosphere  Climate Variability in the Troposphere and Stratosphere  Climate Feedback Processes in the Atmosphere

Global Energy Cycle

Temperature and Pressure

Thermal Energy to Kinetic Energy

Balance of Force in the Horizontal

Properties of the Three Cells

The Three Cells

The Three Cells

Global Distribution of Deserts

Jet Streams Near the Western US

East-West Circulation

How Many Monsoons Worldwide?

Stratosphere: Circulation and Temperature

Satellite View of the Ozone Hole

Stratospheric Sudden Warming  Every other year or so the normal winter pattern of a cold polar stratosphere with a westerly vortex is interrupted in the middle winter.  The polar vortex can completely disappear for a period of a few weeks.  During the sudden warming period, the stratospheric temperatures can rise as much as 40°K in a few days!

Oceans - Outline  Basic Dynamics       From atmospheric winds to oceanic currents       Ekman transport       Geostrophic Currents  Surface Ocean Circulation: Wind-Driven       Subtropicl gyre       Boundary current  Deep Ocean Circulation: Density-Driven      Thermohaline conveyor belt

Subcomponent: Global Oceans

Mixed Layer Processes

Six Great Current Circuits in the World Ocean

Characteristics of the Gyres Currents are in geostropic balance Each gyre includes 4 current components:       two boundary currents: western and eastern       two transverse currents: easteward and westward Western boundary current (jet stream of ocean)        the fast, deep, and narrow current moves warm water polarward  (transport ~50 Sv or greater) Eastern boundary current       the slow, shallow, and broad current moves cold water equatorward (transport ~ 10-15 Sv) Trade wind-driven current        the moderately shallow and broad westward current (transport ~ 30 Sv) Westerly-driven current        the wider and slower (than the trade wind-driven current) eastward current

Step 1: Surface Winds

Step 2: Ekman Layer (frictional force + Coriolis Force)

Ekman Transport

Step 3: Geostrophic Current (Pressure Gradient Force + Corioils Foce)

Thermohaline Circulation

Thermohaline Conveyor Belt

Land Surface - Outline  Climate Role  Surface Energy Balance  Surface Water Balance  Vegetation (Canopy)  Soil (moisture)

Climate Role 1: Albedo è Energy Cycle

Climate Role 2: Transpiration è Water Cycle

Cryosphere – Outline

Why is Ice Important to Climate? Surface ice of any depth is a much more effective reflector of solar radiation than the underlying surface. Sea ice is a good insulator and allows air temperature to be very different from that of the seawater under the ice. At present, year-round ice covers 11% of the land area and 7% of the world ocean.

Solid Earth - Outline  Internal Structure of the Solid Earth Theory of Plate Tectonics History of Plate Tectonics

Tectonic-Scale Climate Change The faint young Sun paradox and its possible explanation. Why was Earth ice-free even at the poles 100 Myr ago (the Mesozoic Era)? What are the causes and climate effects of changes in sea level through time? What caused Earth’s climate to cool over the last 55 Myr (the Cenozoic Era)?

History of Plate Tectonics

Earth’s Thermostat – Chemical Weathering Chemical weathering acts as Earth’s thermostat  and regulate its long-term climate. This thermostat mechanism lies in two facts:       (1) the average global rate of chemical weathering depends on the state of Earth’s climate,       (2) weathering also has the capacity to alter that state by regulating the rate which CO2 is removed from the atmosphere.

Tectonic Control of CO2 Input – The Seafloor Spreading Rate Hypothesis During active plate tectonic processes, carbon cycles constantly between Earth’s interior and its surface. The carbon moves from deep rock reservoirs to the surface mainly as CO2 gas associated with volcanic activity along the margins of Earth’s tectonic plates. The centerpiece of the seafloor spreading hypothesis is the concept that changes in the rate of seafloor spreading over millions of years control the rate of delivery of CO2 to the atmosphere from the large rock reservoir of carbon, with the resulting changes in atmospheric CO2 concentrations controlling Earth’s climate.

Tectonic Control of CO2 Removal – The Uplift Weathering Hypothesis The uplifting weathering hypothesis asserts that the global mean rate of chemical weathering is heavily affected by the availability of fresh rock and mineral surfaces that the weathering process can attack. This hypothesis suggests that tectonic uplifting enhances the exposure of freshly fragmented rock which is an important factor in the intensity of chemical weathering. This hypothesis looks at chemical weathering as the active driver of climate change, rather than as a negative feedback that moderates climate changes.

Climate Change and Variation - Outline Climate Sensitivity and Feedback Past Climate Change El Nino-Southern Oscillation Ozone Depletion

Slide 43

El Nino-Southern Oscillation (ENSO) ENSO is a interannual (year-to-year) climate variability in the eastern tropical Pacific Ocean. ENSO is found to have profound impacts on global climate.

1997-98 El Nino

The 1997 Ozone Hole