HR: 11:50h
AN: B32A-07 INVITED     [Abstracts]
TI: Effects of Aerosols on the Carbon Cycle and on Soil Moisture
AU: * Robock, A
EM: robock@envsci.rutgers.edu
AF: Rutgers University, Department of Environmental Sciences, 14 College Farm Road, New Brunswick, NJ 08901 United States
AU: Li, H
EM: hli@envsci.rutgers.edu
AF: Rutgers University, Department of Environmental Sciences, 14 College Farm Road, New Brunswick, NJ 08901 United States
AB: This talk gives two examples of the effects of aerosols on the carbon and hydrological cycles. Stratospheric aerosols from volcanic eruptions affect the biospheric carbon sink, which may affect the record of volcanic cooling seen in tree rings, and tropospheric aerosol trends (solar dimming) may have affected observed soil moisture trends in the Ukraine. The lack of a larger cooling in proxy records of climate change following large volcanic eruptions such as those of Tambora in 1815 and Krakatau in 1883 has long been a puzzle for climatologists. These records, however, may have been biased by enhanced tree growth for several years following each eruption induced by additional diffuse radiation caused by the stratospheric volcanic aerosol clouds from the eruptions. By comparing proxy reconstructions of climate with and without tree ring data, this effect is demonstrated for the five largest eruptions for the period 1750-1980. When proxy records of Northern Hemisphere climate change are corrected for this proposed diffuse effect, there is no impact on climate change for time scales longer than 20 years. However, it now appears that there was a hemispheric cooling of about 0.6°C for a decade following the unknown volcanic eruption of 1809 and Tambora in 1815, and a cooling of 0.3°C for several years following the Krakatau eruption of 1883. Observations from the longest data set of observed soil moisture available in the world, 47 yr of gravimetrically-observed plant available soil moisture for the top 1 m of soil, observed every 10 days for April-October for 141 stations from fields with either winter or spring cereals from the Ukraine for 1958-2004, show a positive soil moisture trend for the entire period of observation, with the trend leveling off in the last two decades. Using a land surface model forced with observed meteorology and modified solar insolation, we find that an observed downward trend in insolation for the first half of the period produced a downward trend in evaporation and contributed to the upward soil moisture trend.
DE: 0370 Volcanic effects (8409)
DE: 0428 Carbon cycling (4806)
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1866 Soil moisture
SC: Biogeosciences [B]
MN: Fall Meeting 2005