8: Ocean Dust Flashcards
Name the six main inputs of matter into the oceans?
Aeolian dust, organisms, turbidities, ice rafted debris, landslides, bottom water currents
What is the largest input of dust into the oceans at present day?
Sahara and Gobi deserts
What % sediment bulk in Central North Pacific is from dust?
75%
Why is African desert dust welcomed in S. America?
Acts to fertilize the soils there
A dust plume from Gobi occurred on April 4th, by what date did it reach Asia, Pacific and America?
7th, 10th, 13th
What three things can paleoclimatic changes in aridity/rainfall tell us (derived from spatial and temporal distribution of paleo-dust)
Vegetation changes, human impacts, migration of dust belts with time
What four things can time and spatial distribution of dust tell us about paleoclimate?
Record of aridity/rainfall, indication of changes in wind patterns, validation of climate models, grain size indication of wind speed/distance to source
What four ways has dust been shown to respond to climate?
Emission, transport, deposition, post-depositional weathering
Is there more or less Aeolian dust during a glacial (by what factor)?
Increase in dust 2-5x more
What three factors cause the change in dust flux during a glacial?
Location/extent of dust sources, transport path, trapping efficiency of depositional zone
In terms of dust transport, how can we infer changes in paleo-dust particle size?
Changes in pressure gradients and therefore wind speed/gustiness
How does a changing transport path effect paleo-dust distribution?
Length of path and direction of particle rain-out
How can dust in the atmosphere directly effect climate?
Radiative effects
How can dust in the atmosphere indirectly effect climate (two ways)
Modification of clouds (cloud condensation nuclei), ocean uptake of CO2 by Fe fertilization.
What are the radiative properties of haematite and goethite?
High radiative effect, high absorptivity of insolation at short wave lengths
What is the climatic effect of radiative scattering by dust?
Widespread cooling – increased upwards radiance
How does iron fertilization in the ocean work?
Increased iron in ocean increases productivity of marine photo-plankton – increases CO2 uptake
Name four ways in which the source of loess can effect the dust magnetic properties?
Mineralogy of rock, aridity/seasonal aridity, episodic volcanic sources, human sources.
What are the two ways in which transportation can change loess?
Grain size/mineralogy (denser grains settle first), concentration from source
Which magnetic mineral dominated in glacial periods?
Haematite/goethite
Which magnetic mineral dominated in interglacial periods and why?
Magnetite – increase in biogenic magnetite?
What are the three main parameters that are found to be significant in Saharan dust?
High HIRM, low s-ratio, high %Xfd
What is the amount of Arabian Sea Dust dictated by?
Air pressure difference
What is Arabian Sea Dust caused by?
Strong monsoonal climate
