8: Ocean Dust

Question 1

Name the six main inputs of matter into the oceans?

Answer 1

Aeolian dust, organisms, turbidities, ice rafted debris, landslides, bottom water currents

Question 2

What is the largest input of dust into the oceans at present day?

Answer 2

Sahara and Gobi deserts

Question 3

What % sediment bulk in Central North Pacific is from dust?

Answer 3

75%

Question 4

Why is African desert dust welcomed in S. America?

Answer 4

Acts to fertilize the soils there

Question 5

A dust plume from Gobi occurred on April 4th, by what date did it reach Asia, Pacific and America?

Answer 5

7th, 10th, 13th

Question 6

What three things can paleoclimatic changes in aridity/rainfall tell us (derived from spatial and temporal distribution of paleo-dust)

Answer 6

Vegetation changes, human impacts, migration of dust belts with time

Question 7

What four things can time and spatial distribution of dust tell us about paleoclimate?

Answer 7

Record of aridity/rainfall, indication of changes in wind patterns, validation of climate models, grain size indication of wind speed/distance to source

Question 8

What four ways has dust been shown to respond to climate?

Answer 8

Emission, transport, deposition, post-depositional weathering

Question 9

Is there more or less Aeolian dust during a glacial (by what factor)?

Answer 9

Increase in dust 2-5x more

Question 10

What three factors cause the change in dust flux during a glacial?

Answer 10

Location/extent of dust sources, transport path, trapping efficiency of depositional zone

Question 11

In terms of dust transport, how can we infer changes in paleo-dust particle size?

Answer 11

Changes in pressure gradients and therefore wind speed/gustiness

Question 12

How does a changing transport path effect paleo-dust distribution?

Answer 12

Length of path and direction of particle rain-out

Question 13

How can dust in the atmosphere directly effect climate?

Answer 13

Radiative effects

Question 14

How can dust in the atmosphere indirectly effect climate (two ways)

Answer 14

Modification of clouds (cloud condensation nuclei), ocean uptake of CO2 by Fe fertilization.

Question 15

What are the radiative properties of haematite and goethite?

Answer 15

High radiative effect, high absorptivity of insolation at short wave lengths

Question 16

What is the climatic effect of radiative scattering by dust?

Answer 16

Widespread cooling – increased upwards radiance

Question 17

How does iron fertilization in the ocean work?

Answer 17

Increased iron in ocean increases productivity of marine photo-plankton – increases CO2 uptake

Question 18

Name four ways in which the source of loess can effect the dust magnetic properties?

Answer 18

Mineralogy of rock, aridity/seasonal aridity, episodic volcanic sources, human sources.

Question 19

What are the two ways in which transportation can change loess?

Answer 19

Grain size/mineralogy (denser grains settle first), concentration from source

Question 20

Which magnetic mineral dominated in glacial periods?

Answer 20

Haematite/goethite

Question 21

Which magnetic mineral dominated in interglacial periods and why?

Answer 21

Magnetite – increase in biogenic magnetite?

Question 22

What are the three main parameters that are found to be significant in Saharan dust?

Answer 22

High HIRM, low s-ratio, high %Xfd

Question 23

What is the amount of Arabian Sea Dust dictated by?

Answer 23

Air pressure difference

Question 24

What is Arabian Sea Dust caused by?

Answer 24

Strong monsoonal climate

Question 25

Explain the Arabian Sea Dust phenomenon in terms of wind direction and productivity

Answer 25

North-Easterly winds in winter – dust from S. Asia, South-Westerly winds in summer induce high marine productivity

Question 26

When studying monsoon intensity, what magnetic parameter does dust content has the strongest relationship to?

Answer 26

Xlf – entirely paramagnetic

Question 27

What are the two components of the sediment system found when linking dust to monsoon intensity?

Answer 27

Diamagnetic carbonates, Paramagnetic minerals (Xlf high)

Question 28

How do we relate monsoon intensity, insolation and dust volume?

Answer 28

More dust transported when more solar energy (aridity), thus summer insolation which dictates the monsoon intensity

Question 29

In the Indian Ocean case study, what was the cause of susceptibility depletion below 0.2ma?

Answer 29

Iron oxide depletion as poor oxygen environment so organics used to obtain oxygen

Question 30

In terms of ocean floor dust, what two possible things could cause peaks in HIRM?

Answer 30

Dust peak or dissolution remanence