We now know that dust can travel great distances, even on an intercontinental scale. The purpose of this task is to investigate the role of dust in climate change, the role of dust in enhancement of primary productivity in the oceans, and the role of dust in soil formation. New modeling efforts by atmospheric scientists are demonstrating that depending on particle size and composition, dust can have either a warming or cooling effect on the atmosphere. Addition of dust can also increase primary productivity in the world's oceans, which in turn can draw down atmospheric carbon dioxide and result in a "reverse" greenhouse effect. Finally, it is now recognized that eolian addition to soils in many environments is a more important process than previously supposed. A major effort of this task is, therefore, to assess the degree to which dust has added to soils in North America, from the tropics to the Arctic.
Figure 17: Aerosol index maps (compiled from Nimbus 7 satellite imagery, using the Total Ozone Mapping Spectrometer (TOMS)) for January and July, 1988, showing seasonal shifts in the magnitude and location of African dust transport. Redrawn from data generated by the Ozone Processing Team at NASA's Goddard Space Flight Center.
Figure 18a: Aerial photograph of a part of St. Michael Island in western Alaska, showing Zagoskin Lake, other maar lakes and simplified geology.
Figure 18b: Depth plots of SiO2, CaO and MgO in Zagoskin Lake sediments, with gray-shaded bands showing the range of these values in Fairbanks, Alaska loesses and local St. Michael Island basalts. Calibrated radiocarbon ages are also shown. Note that the plots show that the lake sediments are similar to loess and differ greatly from the local bedrock, suggesting they are derived from a distant, wind-blown source. See Muhs et al., 2003, Quaternary Research.
Figure 19a: Examples of dust transport from mainland California and Baja California to the eastern Pacific Ocean and the California Channel Islands under recent Santa Ana wind conditions:
(a) Multi-angle Imaging SpectroRadiometer (MISR) image from the Terra spacecraft (orbit 11423), 9 February 2002 [courtesy of NASA/GSFC/LaRC/JPL, MISR Team]; (b) true-color image from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua spacecraft, 6 January 2002 [courtesy of Jeff Schmaltz, NASA/GSFC/MODIS Rapid Response Team];
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(c) false-color, nadir image from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua spacecraft, 27 November 2003; plumes from the mainland to the Channel Islands in this image consist of dust, but also ash from recently burned areas on the mainland [courtesy of Jacques Descloitres, NASA/GSFC/MODIS Rapid Response Team]. |
Figure 19b: Photographs of silt-rich surface mantles and associated features on San Clemente Island. (a) Alfisol with silt-mantle overlying clay-rich subsoil on marine terrace 2b, dated to approximately 120 ka. (b) hand specimens showing color contrast between silt-rich surface mantle and clay-rich subsoil of Vertisol on marine terrace 5, estimated to be approximately 575 ka. (c) biological (biogenic) soil crust on surface of silt mantle on Vertisol on terrace 5.
Figure 19c: Ternary plots showing relative proportions of immobile elements Scandium (Sc), Thorium (Th), and Lanthanum (La) in (a) silt fractions (53-2 µm), (b) clay fractions (< 2 µm), and (c) sand fractions (2000-53 µm) of silt mantles (open circles) on San Clemente Island, Santa Cruz Island, Santa Barbara Island, and East Anacapa Island. The plots show that silt, and perhaps much of the clay in these topsoils are derived from Mojave Desert dust and not the local bedrock.
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Figure 21: Young glacial moraines such as these (a and b) are common in the alpine zone above treeline in the Talkeetna Mountains of southern Alaska (see Figure 20 for location). The moraines are mantled with silt-rich soils (c) which abruptly overlie glacial till composed of the local granodiorite bedrock (d). The silts have a composition that differs from the bedrock, indicating that they have an exotic, eolian origin. Silt-rich soils such as these may be important for helping to sustain a rich tundra vegetation community. |
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Eolian History home page | Task 1 | Task 2
Muhs, D.R., 2001, Evolution of soils on Quaternary reef terraces, Barbados, West Indies: Quaternary Research, v. 56, p. 66-78. [DOWNLOAD PDF]
Muhs, D.R., Ager, T.A., Been, J., Bradbury, J.P., and Dean, W.E., 2003, A late Quaternary record of eolian silt deposition in a maar lake, St. Michael Island, western Alaska: Quaternary Research, v. 60, p. 110-122. [DOWNLOAD PDF]
Muhs, D.R., and Benedict, J.B., 2006, Eolian additions to late Quaternary alpine soils, Indian Peaks Wilderness Area, Colorado Front Range: Arctic, Antarctic and Alpine Research, v. 38, p. 120-130. [DOWNLOAD PDF]
Mahowald, N., Muhs, D.R., Levis, S., Yoshioka, M., Zender, C., and Rasch, P., 2006, Change in atmospheric mineral aerosols in response to climate: Last glacial period, pre-industrial, modern and doubled carbon dioxide climates: Journal of Geophysical Research, v. 111, D10202, doi: 10.1029/2005JD006653. [DOWNLOAD PDF]
Muhs, D.R., Budahn, J., Prospero, J.M., and Carey, S.N., 2006, Rare earth element geochemical evidence for Saharan dust inputs to soils of western Atlantic islands: Barbados, the Bahamas and Florida: Journal of Geophysical Research, in revision.
Muhs, D.R., Budahn, J., Reheis, M., Beann, J., Skipp, G., and Fisher, E., 2006, Airborne dust transport to the eastern Pacific Ocean off southern California: San Clemente Island revisited: Journal of Geophysical Research, in review.
Muhs, D.R., 2006, Eolian sediments and processes, in Gornitz, V. (Ed.), Encyclopedia of Paleoclimatology and Ancient Environments, Kluwer Academic Publishers, Dordrecht, The Netherlands, in press.
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Figure 20: True-color image of southern Alaska from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua spacecraft, taken 14 September 2003, showing study areas in the Talkeetna Mountains, Alaska Range, and St. Michael Island. Note dust plumes to the southeast of the Chugach Mountains [image courtesy of Jeff Schmaltz, NASA/GSFC/MODIS Rapid Response Team].