Subaquatic Dust Deposits - Mineral Dust: A Key Player in the Earth System - page 440

d 18 O (‰ PDB)
(Lisiecki & Raymo, 2005)

d 18 O (‰ VSMOW)
(NGRIP, 2005)

d 18 O (‰ PDB)
(Shanahan et al., 2009)

2 3456 - 4 8 -44 -40 -36 -32 - 1 0 1 2 3 4 5

0 0 0

1

10 500

2

1000

20

3

30 1500

4

40 2000

5

2500

50

6

7 60 3000

0 20 40 60

wt.% dust ODP885/886
(Snoeckx et al., 1995)

100 80 60 40 20 0 20 30 40 50 60 70

vol.% dust GeoB9501
(Mulitza et al., 2010)

vol.% dust GeoB9508
(Mulitza et al., 2008)

Fig. 17.4 Comparison of marine dust records at three different time scales. All black plots depict
• 18 O records, which are used as global temperature proxy. From left to right these are the global
• 18 O stack by Lisiecki and Raymo ( 2005 ), the • 18 O record from the Greenland NGRIP ice core
(NorthGRIP community members 2004 )andthe• 18 O record from Lake Bosumtwi by Shanahan
et al. ( 2009 ). Note the scales of the time axes changing from left to right from myr, kyr to yr
before present. The grey records depict dust records defined as the non-soluble fraction of marine
sediments from Snoeckx et al. ( 1995 ), Mulitza et al. ( 2008 ) and Mulitza et al. ( 2010 ), respectively.
Note that the x-axis of the Mulitza et al. 2008 record is reversed

easily recognised in these sediments by a downwind decrease in both dust particle
size and dust flux. The same conclusion can be drawn from satellite observations
of the modern Saharan dust plume travelling westward over the equatorial North
Atlantic Ocean; Figure 17.5 also shows how the aerosol index of the Total Ozone
Mapping Spectrometer (TOMS) locates both the presently most active dust sources
in northwest Africa but also how the modern Saharan dust plume over the Atlantic
Ocean is centred at about 12 ı N. These downwind gradients in both flux and particle
size are key issues in the role that wind-blown dust may have as a player of
environmental change.
The sediment archive that can be found on the sea floor is always a mixture of
various components like erosion products from land, plankton and algal remains
from the surface ocean and biogenic components from the sea floor. The erosion
products from land are transported to the ocean by rivers, winds and ice. On nearly
all parts of the sea floor in the (sub)tropical oceans, the land-derived fraction is -
in the absence of ice - a mixture of river load and wind-blown dust. Even when
nowadays no active river systems are present, environmental conditions throughout