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Titel |
Observed 20th century desert dust variability: impact on climate and biogeochemistry |
VerfasserIn |
N. M. Mahowald, S. Kloster, S. Engelstaedter, J. K. Moore, S. Mukhopadhyay, J. R. McConnell, S. Albani, S. C. Doney, A. Bhattacharya, M. A. J. Curran, M. G. Flanner, F. M. Hoffman, D. M. Lawrence, K. Lindsay, P. A. Mayewski, J. Neff, D. Rothenberg, E. Thomas, P. E. Thornton, C. S. Zender |
Medientyp |
Artikel
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Sprache |
Englisch
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ISSN |
1680-7316
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Digitales Dokument |
URL |
Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 22 ; Nr. 10, no. 22 (2010-11-19), S.10875-10893 |
Datensatznummer |
250008900
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Publikation (Nr.) |
copernicus.org/acp-10-10875-2010.pdf |
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Zusammenfassung |
Desert dust perturbs climate by directly and indirectly interacting with
incoming solar and outgoing long wave radiation, thereby changing
precipitation and temperature, in addition to modifying ocean and land
biogeochemistry. While we know that desert dust is sensitive to
perturbations in climate and human land use, previous studies have been
unable to determine whether humans were increasing or decreasing desert dust
in the global average. Here we present observational estimates of desert
dust based on paleodata proxies showing a doubling of desert dust during the
20th century over much, but not all the globe. Large uncertainties
remain in estimates of desert dust variability over 20th century due to
limited data. Using these observational estimates of desert dust change in
combination with ocean, atmosphere and land models, we calculate the net
radiative effect of these observed changes (top of atmosphere) over the
20th century to be −0.14 ± 0.11 W/m2 (1990–1999 vs. 1905–1914).
The estimated radiative change due to dust is especially strong between the
heavily loaded 1980–1989 and the less heavily loaded 1955–1964 time periods
(−0.57 ± 0.46 W/m2), which model simulations suggest may have reduced
the rate of temperature increase between these time periods by 0.11 °C.
Model simulations also indicate strong regional shifts in precipitation and
temperature from desert dust changes, causing 6 ppm (12 PgC) reduction in
model carbon uptake by the terrestrial biosphere over the 20th century.
Desert dust carries iron, an important micronutrient for ocean
biogeochemistry that can modulate ocean carbon storage; here we show that
dust deposition trends increase ocean productivity by an estimated 6%
over the 20th century, drawing down an additional 4 ppm (8 PgC) of
carbon dioxide into the oceans. Thus, perturbations to desert dust over the
20th century inferred from observations are potentially important for
climate and biogeochemistry, and our understanding of these changes and
their impacts should continue to be refined. |
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