Plate Tectonic and Ocean Bathymetry

Effects of Volcanic eruptions on the solar incoming radiation

Agung1963

Pinatubo1991

Chichón1982

Pinatubo facts:•Earthquakes & evacuations prior to eruption•9 hours eruption with 300 meters of mountain loss•15 and 30 million tons of sulfur dioxide gas.•Tropical Storm Yunya triggers rainfall of ashes (33 cm layers) •200 – 800 deaths•Ashes reaches stratosphere (34 km high) a cooling up to 0.73 C

Cartoon of Volcanic Impacts on the Earth Heat BudgetRobock, Reviews of Geophysics, 38, 2 / May 2000

Volcanic Impacts on Ocean and Climate

1. Warmer Stratosphere and Cooler earth surface if eruption reaches stratosphere

2. Stronger JET stream in the Northern Hemisphere and warmer winter on continents (non-linear effects)

3. Diurnal Cycle may be reduced in amplitude

4. Hypothesis that Volcanic eruptions may trigger El Nino? Theoretical basis:* perturbation in the heat budget may lead to a reduction in the trade winds.

* uniform cooling in the tropics results in an east-west asymmetric response in the Sea Surface Temperature leading to a reduction in the trades.

Feedbacks:ENSO/Climate change Atmospheric Circulation or Ice Loading change Litoshperic Stresses Eruptions!

The Physiography of the North Atlantic Ocean Floor

http://topex.ucsd.edu

continental margins

deep oceanbasins midoceanic

ridges

Mid-Oceanic ridges & Hydrothermal Vents

Mid-Oceanic ridges are also a source of geo-heating …

The Ocean Circulation is generally considered to be forced by wind stress, heat and freshwater fluxes at the sea surface.

However

Sources of heat to our planet:•solar radiation 100 W m-2

•geothermal inputs 0.05-0.2 W m-2

•Tides (small)

Estimates of the Effects of Geothermal Heating on the mean temperature profiles in the World Ocean

Atlantic Ocean

IndianOcean

Changes in the Vertical Circulation of the Ocean

(Thermohaline Circulation)

Why ocean bathymetry?

•How do we measure bathymetry?

•Why is ocean bathymetry important?

Questions:

How do we measure bathymetry?

What does it mean to be at an altitude of 4000 m?

It mean that I am 4000 m above the Mean Sea Level (MSL)

Model of the shape of the Earth

http://www.esri.com/news/arcuser/0703/geoid1of3.html http://en.wikipedia.org/wiki/Geoid

geoid: The equipotential surface of the Earth's gravity field which best fits, in a least squares sense, global mean sea level (MSL)

The height of the Earth surface

Why ocean bathymetry?

Ocean Circulation and ClimateHeat Transport affected by topography!

Ocean Circulation and ClimateOcean Currents take different paths!

Ocean Circulation and ClimateDeep ocean mixing and pathways

Ocean Circulation and ClimateMixing energy and dissipation of tides!

Ocean Circulation and BiologySeamounts ….

Societal impactsTsunami

Societal impactsGas and oil extraction

1) Reading material on Class Website

Satellite Topography and Oceanography from Space

2) Homework #2 assigned.

Due next Wed. Sept. 15, 2010

Before you go …

31.03 g/cm WATER

A

B C

30.95 g/cm

31.00 g/cm

31.10 g/cm

h=5 cm

h=10 cm

h=1 cm

Figure 1

31.03 g/cm WATER

A

B C

30.95 g/cm

31.00 g/cm

31.10 g/cm

h=5 cm

h=10 cm

h=1 cm

Figure 1

Understanding Isostacy and BuoyancyExercise

31.03 g/cmw

WATER Level

A

31.00 g/cmA

Lake Bottom

w w wp gh [ ]A A A wp g h h

Ah

h

( )out w Ah h h h

wh

31.03 g/cmw

WATER Level

A

31.00 g/cmA

Lake Bottom

w w wp gh [ ]A A A wp g h h

Ah

h

( )out w Ah h h h

wh

WATER Level

2D rDiameter

2 ( )3out

out out

hV h r

We know the Vout.

To find hout we can use the formula for the volume of a partial sphere given by:

outh

center

r

Now solving for hout may not be easy since it involves a cubic polynomial, however you can plot hout vs. Vout and read the approximate value of hout of the graph.

outV

h

0.85outh cmV

outh

WATER Level

2D rDiameter

2 ( )3out

out out

hV h r

We know the Vout.

To find hout we can use the formula for the volume of a partial sphere given by:

outh

center

r

Now solving for hout may not be easy since it involves a cubic polynomial, however you can plot hout vs. Vout and read the approximate value of hout of the graph.

outV

h

0.85outh cmV

outh