Last Glacial Maximum and Late Holocene Eolian Fluxes: Readme file
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              World Data Center for Paleoclimatology, Boulder
                                and 
                   NOAA Paleoclimatology Program
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NOTE: PLEASE CITE ORIGINAL REFERENCE WHEN USING THIS DATA!!!!!

NAME OF DATA SET: Last Glacial Maximum and Late Holocene Eolian Fluxes
LAST UPDATE: 3/2001 (Original Receipt by WDC Paleo)  

CONTRIBUTOR: Karen E. Kohfeld and Margareta Hansson

IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2001-032

SUGGESTED DATA CITATION:
Kohfeld, K. E. and Hansson, M.  LGM and Late Holocene Eolian Fluxes 
from Ice Cores, Marine Sediment Traps, and Marine Sediments, 
IGBP PAGES/World Data Center for Paleoclimatology 
Data Contribution Series #2001-032.  
NOAA/NGDC Paleoclimatology Program, Boulder CO, USA. 


ORIGINAL REFERENCE: Mahowald, N., Kohfeld, K. E., Hansson, M., 
Balkanski, Y., Harrison, S. P., Prentice, I. C., Schulz, M., and 
Rodhe, H., 1999.  Dust sources and deposition during the 
Last Glacial Maximum and current climate: A comparison of 
model results with palaeodata from ice cores and marine sediments. 
Journal of Geophysical Research 104, 15, 895-15, 916.

GEOGRAPHIC REGION: Global
PERIOD OF RECORD: Last Glacial Maximum and Late Holocene

LIST OF FILES: Readme_DIRTMAP.txt (this file), 
DIRTMAP_Table1.doc, DIRTMAP_Table2.doc (Microsoft Word Format).
DIRTMAP Table1 – Dust deposition fluxes retrieved from ice cores
DIRTMAP Table 2a – Eolian Fluxes to Marine Sediments
DIRTMAP Table2b – Eolian Fluxes to Marine Sediment Traps


DESCRIPTION:  
Records of dust accumulation can be obtained from several paleoenvironmental 
archives, including ice cores, marine sediment records, lacustrine sediment 
records, and loess. The data here represent the first version of the DIRTMAP 
data base and include information from both marine sediments and ice cores. 
Table 1 includes information on dust concentrations (both particle number and mass), 
ice accumulation rates, and LGM/Current ratios for both concentrations and fluxes.  
Dust fluxes were only estimated where a mass concentration was provided.  
Table 2a represents dust (terrigenous) fluxes to modern marine sediment traps.  
Sites where sampling periods were less than 50 days (and therefore are likely 
to be biased to a seasonal estimate) are noted.  Table 2b provides information 
about dust (terrigenous) fluxes to surface sediments, and LGM/coretop ratios 
of dust fluxes.

ICE CORE DATA
Dust concentrations in the ice are measured by several different techniques 
and, as a result, are expressed in several different ways (e.g. total insoluble 
mass as measured by laser light scattering, Al concentration measured by atomic 
absorption, and Coulter Counter measurements of number particle concentrations). 
We assume that all the methods yield broadly comparable results, although there 
are differences in calculated ratios depending on whether mass- or number-based 
concentrations are used. Ice core dust deposition is expressed here as deposition 
fluxes and not dust concentration in the ice core. This ensures consistency with 
the marine sediment data. The disadvantage of converting ice core data from 
concentration to fluxes is that this calculation relies upon estimated ice 
accumulation rates.

We calculate LGM/current changes in dust deposition fluxes from changes of the 
dust concentration in the ice and changes of the snow accumulation rate, assuming
that the LGM snow accumulation rates were lower than Holocene rates by a factor 
of 2 on Antarctica and lower by a factor of 2-5 on Greenland. (Dust deposition 
fluxes are the dust concentrations times the ice accumulation rate.) In the ice 
core studies where only particle number concentrations were reported, only the 
ratio between LGM and current is shown because it is not straightforward to 
convert from number concentration to mass concentration. In two cases, the 
LGM/current concentration ratio is estimated from a reported figure 
(Hammer et al., 1985; Thompson et al., 1989; Thompson et al., 1995), 
while otherwise, the reported values are shown. The time intervals compared may 
vary between the different locations due to variations in reporting.

The LGM value is either the mean of the interval 15-30 kyr B.P. or the mean 
of samples from a shorter period within that interval. The current value is 
the mean for the Holocene (0-10 kyr B.P.) or the mean of samples from a 
shorter period within that interval. 

MARINE DATA
Eolian deposition rate data were compiled from the literature, for both sediment 
traps and marine sediments. Sediment trap eolian deposition rates were determined 
by eliminating organic carbon, carbonate, and opal from total particles, a general 
procedure which is described in(Honjo et al., 1982). Lithogenic fluxes in sediment 
traps are estimated according to (Wefer and Fischer, 1993):

Lithogenic flux = Total flux – (opal flux + carbonate flux + (2*organic carbon flux)).

In the Pacific Ocean, some fluxes were estimated from Al (Saito et al., 1992), 
assuming that terrigenous material is 8% Al. The data measures seasonal to annual 
fluxes, since the sediment traps were deployed for 176-1626 days, with the 
exception of two Pacific Ocean studies (Noriki and Tsunogai, 1986; Saito et al., 1992) 
which sampled mostly 14-30 day periods. 

Eolian accumulation rates (MAReol) for marine sediments are generally calculated as:

MAReol (g/m2/yr) = LSR (m/yr) x BD (g/m3) x f;

where LSR is linear sedimentation rate, BD is sediment bulk density 
(standard error = ±10-25%), and f is the measured eolian fraction of the sediment sample 
(standard error = ±10-40%). 

Sediment age models were determined using radiocarbon dates where available 
(Ruddiman, 1997; Sirocko and Lange, 1991), and the SPECMAP oxygen isotope time scale 
[e.g., (Imbrie et al., 1984) everywhere else. The samples represent average values 
over periods of several thousand years. The surface sediment samples generally 
represent the average for the Holocene, but the precise periods vary from data set 
to data set (e.g., 3-11 kyr B.P. in Atlantic Ocean (Ruddiman, 1997); 0-8 kyr B.P. 
in Indian Ocean (Sirocko et al., 1991)). For the LGM, the values given in Table 2b 
are averages for the interval 18 ±2 kyr B.P., except for sites derived from the 
(Ruddiman, 1997) and (Sirocko and Lange, 1991) studies which both give averages 
over the interval 15 to 25 kyr B.P. 

For full documentation (including references) see (Mahowald et al., 1999) or 
contact kek@bgc-jena.mpg.de.


REFERENCES:

Hammer, C. U., Clausen, H. B., Dansgaard, W., Neftel, A., Kristinsdottor, P., 
and Johnson, E. (1985). Continuous impurity analysis along the Dye 3 deep core. 
In "Greenland Ice Core: Geophysics, Geochemistry, and the Environment." 
(C. Langway Jr., H. Oeschger, and W. Dansgaard, Eds.), pp. 90-94. 
Geophys. Monogr. AGU, Washington DC.

Honjo, S., Manganini, S. J., and Poppe, L. J. (1982). Sedimentation of lithogenic 
particles in the open sea. Marine Geology 50, 199-220.

Imbrie, J., Hays, J. D., Martinson, D. G., McIntyre, A., Mix, A. C., Morley, J. J., 
Pisias, N. G., Prell, W. L., and Shackleton, N. J. (1984). The orbital theory of 
Pleistocene climate: support from a revised chronology of the marine d18O record. 
In "Milankovitch and Climate Part 1." (A. Berger, J. Imbrie, J. Hays, G. Kukla, 
and B. Saltzman, Eds.), pp. 269-305. NATO ASI Series C: Mathematical and Physical Sciences.
D. Reidel Publishing Company, Dordrecht.

Mahowald, N., Kohfeld, K. E., Hansson, M., Balkanski, Y., Harrison, S. P., Prentice, I. C., 
Schulz, M., and Rodhe, H. (1999). Dust sources and deposition during the Last Glacial 
Maximum and current climate: A comparison of model results with palaeodata from ice 
cores and marine sediments. Journal of Geophysical Research 104, 15,895-15,916.

Noriki, S., and Tsunogai, S. (1986). Particulate fluxes and major components of 
settling particles from sediment trap experiments in the Pacific Ocean. 
Deep-Sea Research 33, 903-912.

Ruddiman, W. F. (1997). Tropical Atlantic terrigenous fluxes since 25,000 yrs B.P. 
Marine Geology 136, 189-207.

Saito, C., Noriki, S., and Tsunogai, S. (1992). Particulate flux of Al, a component 
of land origin, in the western North Pacific. Deep-Sea Research 39, 1315-1327.

Sirocko, F., and Lange, H. (1991). Clay-mineral accumulation rates in the Arabian Sea 
during the late Quaternary. Marine Geology 97, 105-119.

Sirocko, F., Sarnthein, M., Lange, H., and Erlenkeuser, H. (1991). 
Atmospheric summer circulation and coastal upwelling in the Arabian Sea 
during the Holocene and the Last Glaciation. Quaternary Research 36, 72-93.

Thompson, L. G., Mosley-Thompson, E., Davis, M. E., Bolzan, J. F., Dai, J., 
Yao, T., Gundestrup, N., Wu, X., Klein, L., and Xie, Z. (1989). 
Holocene-late Pleistocene climatic ice core records from Qinghai-Tibetan plateau. 
Science 246, 474-477.

Thompson, L. G., Mosley-Thompson, E., Davis, M. E., Lin, P.-N., Henderson, K. A., 
Cole-Dai, J., Bolzan, J. F., and Liu, K.-b. (1995). Late Glacial Stage and Holocene 
tropical ice core records from Huascaràn, Peru. Science 269, 46-50.

Wefer, G., and Fischer, G. (1993). Seasonal patterns of vertical particle flux in 
equatorial and coastal upwelling areas of the eastern Atlantic. 
Deep-Sea Research 40, 1613-1645.