January 9 lecture

Question 1

What is the First reason why the ocean is difficult to study?

Answer 1

“Seeing”

Water is a more efficient absorber of electromagnetic radiation than the atmosphere, meaning that we cannot see most of the ocean Optically

Question 2

Is radar and other oceanography instruments effected by the oceans ability to absorb electromagnetic radiation?

Answer 2

Yes, Radar and Sonar still use portions of the electromagnetic spectrum to examine the ocean.

Question 3

What is the second reason why the ocean is difficult to study? ( 3 things included )

Answer 3

“Inaccessibility”

• We can’t breathe water
• The ocean is very deep with the avarge depth being almost 4km
• Most of the ocean is remote from the sea surface

Question 4

Why is it hard to sample deep ocean water?

Answer 4

In order to take a sample of deep ocean water you must lower an instermant on a wire to reach the depth, and this can take hours.

Question 5

Why are Ships a reason why studying the ocean is difficult?

Answer 5

Sea ships are slow, moving around 20km/hr, meaning that it takes long periods of time to reach distant parts of the ocean.

Question 6

What is the cost of one day of operation for a Deep ocean ship?

Answer 6

$40,000

Question 7

What is the third reason why it is difficult to study the ocean?

Answer 7

“Pressure”

- Ocean pressure incenses by 1-atm every 10m you descend

Question 8

What would the atmospheric pressure be at 110m depth?

Answer 8

12x the pressure than at sea level.

Question 9

Why are submersible instruments a reason for why it is difficult to study the ocean?

Answer 9

They need to be disgined to survive great amounts of pressure, thus meaning that they cost lots of money.

Question 10

What is the Fourth reason for why it is difficult to study the ocean? ( kinda three things in one )

Answer 10

Conductivity/Corrosion/Fouling

Question 11

How does conductivity affect how difficult it is to study the ocean?

Answer 11

Because sea water conducts electricity, it can cause short circuits to electrical equipment, meaning we need special water tight electrical items

Question 12

how does corrosion affect how difficult it is to study the ocean?

Answer 12

Seawater is corrosive, Meaning that special metals must be used so that they do not rust or corrode.

Question 13

What is fouling? and how dose it affect how hard it is to study the ocean?

Answer 13

It is when sea creatures grow on equipment.

This casuses difficulties for instruments with moving parts

Question 14

What is the 5th reason why it is difficult to study the ocean?

Answer 14

“Wave motion”

The dynamic movement of the oceans surface.

Question 15

How does wave motion affect how difficult it is to study the ocean? ( three things )

Answer 15

It causes problems with working on moving ships:

• Seasickness
• Deploying instruments
• Rapidly changing conditions

Question 16

What was the original method for measuring Bathymetry?

Answer 16

You would let out rope with a weight on the end until it hit the bottom.

It was called Sounding

Question 17

What unit was originally used to measure depth when sounding?

Answer 17

they used Fathoms = the length on a sailors outstretched arms defined as 6ft

shown with a tied knot every six feet to measure it

Question 18

How was sounding adapted over time? What changes did they make?

Answer 18

The rope was later changed to piano wire with a weight at the end, deployed with a wench

Question 19

What is the biggest problem with measuring bathynetry?

Answer 19

Determining when the weight hit the bottom.

Question 20

Why is it hard to determine when the weight hit the bottom? ( two things )

Answer 20

• It can take multiple Km of line, and it can continue to pull after it has struck bottom.
• Currents can cause the weight to drift sideways increasing the measured distance.

Question 21

What is echo sounding?

Answer 21

It is a method of measuring Bathymtery where you transmit bursts of 10-30 kHz of sound and listen for the echo of the sea floor.

Question 22

How do you measure distance using Echo sounding?

Answer 22

2 x Distance = Velocity x time

Question 23

What are the limitations of Echo sounding?

Answer 23

• Tracks are not well distributed

- Arvarges over some region of the ocean

Question 24

Why is data collected from Echo Sounding usually inaccurate?

Answer 24

The sound cone spreads out the deeper it gets, and if the sea floor is uneven it will measure the average depth, thus making accurate readings unattainable.

Question 25

What is Multibeam Echo sounding?

Answer 25

A modern Bathymetry measuring method, using multiple simultaneous sound frequencies to more accurately measure sea depth.

Question 26

What is seabeam?

Answer 26

It is the first Multibeam Echo Sounder

maps sea floor strips of up to 60km wide.

Question 27

What is Side Scan Sonar?

Answer 27

A device that can be towed behind a boat, that accurately measures bathymetric data

Question 28

How can we use satellites to measure the seas topography?

Answer 28

The satellite measures the sea surface topography, can measure the hight of the sea surface up to 3- 6 cm accuracy.

Question 29

how can satellites tell if there is an under sea mountain or crevasse.

Answer 29

Since rock is denser than water and heavier it has a higher gravitational attraction, the sea surface is slightly higher over these spots.

Question 30

What is the reason behind how water is higher about undersea mountains

Answer 30

The undersea mountain is pulling water towards it, making it pile up over it, rising the sea surface.