記錄 6 之 20
Record:   Prev Next
作者 Buenning, Nikolaus Howard
書名 The impact of hydrological and climatic variations on the oxygen-18 content of atmospheric carbon dioxide
國際標準書號 9781124386591
book jacket
說明 191 p
附註 Source: Dissertation Abstracts International, Volume: 72-02, Section: B, page: 0735
Advisers: David C. Noone; Darin Toohey
Thesis (Ph.D.)--University of Colorado at Boulder, 2010
The 18O composition of atmospheric CO2 is a potentially valuable tracer of global interactions between the hydrologic and carbon cycles. The observed 18O composition of atmospheric CO2 (hereafter deltaCa, where delta=( R/Rstandard-1) x 1000 and R is the molar ratio of heavy to light isotopes) does not show a clear long-term trend, though almost all monitoring stations observed an impressive decrease in deltaCa from 1992 to 1998. The cause(s) of this and other interannual deltaCa variations are still relatively unknown, and this work aims to better understand the driving mechanisms that caused the observed interannual deltaC a variations
Observed interannual deltaCa anomalies from Mauna Loa were correlated with anomalies of certain meteorological variables that could potentially affect deltaCa. Negative correlation existed between deltaCa and both relative humidity and precipitation amount within parts of the tropics. Positive correlations existed between deltaCa variations and the 18O content of precipitation for the same tropical regions. Rough estimates suggest that about 20% of the decrease in deltaCa during the 1990s was due to increases in relative humidity and about 80% of the decrease was due to decreases in the delta 18O value of precipitation (and likely a consequence of increases in the amount of precipitation)
A global model was constructed to simulate atmospheric CO2 and CO18O (and thus deltaCa). This model employed an isotopic land model (ISOLSM) and the Community Atmosphere Model (CAM). The model is used for a series of sensitivity experiments to better understand how both steady-state and interannual varying deltaCa respond to changes in relative humidity, delta18O values of precipitation and water vapor, temperature, and light levels. deltaCa responded the most to changes in the delta 18O values of precipitation and water vapor, with moderate responses to relative humidity changes. Model results suggest that the decrease in deltaCa during the 1990s was due primarily to decreases in the 18O composition of precipitation with a smaller a contribution from increased relative humidity. Thus, observations of deltaCa may become a powerful integrative tool in the coming decades for monitoring large scale changes in the hydrological cycle should it accelerate under a warming climate, as predicted
School code: 0051
Host Item Dissertation Abstracts International 72-02B
主題 Atmospheric Chemistry
Climate Change
Biogeochemistry
0371
0404
0425
Alt Author University of Colorado at Boulder. Atmospheric and Oceanic Sciences
記錄 6 之 20
Record:   Prev Next