AGU journal highlights -- July 23, 2008(rogressively earlier each year. Most stu...)

Date:7/24/2008

rogressively earlier each year. Most studies of the risk associated with early blooming use simple increases in monthly mean temperatures to represent future climate scenarios. However, both the average and the variation of daily temperatures are forecast to increase in future climate scenarios; such variation in temperatures increases the risk that early bud-breaks are followed by damaging frost. To study such frost risk to vegetation, Rigby and Porporato developed a probabilistic model that represents bud-break in the context of fluctuating but warming temperatures. After calibrating this model to temperature data from Durham, N. C., the authors find that model results show that frost risk is equally sensitive to increases in daily temperature fluctuations (which serves to increase frost risk) as to increases in average temperatures (which serves to decrease frost risk).

Title: Spring frost risk in a changing climate

Authors: J. R. Rigby and Amilcare Porporato: Department of Civil and Environmental Engineering, Duke University, Durham, North Carolina, U.S.A.

Source: Geophysical Research Letters (GRL) paper 10.1029/2008GL033955, 2008; http://dx.doi.org/10.1029/2008GL033955

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4. Martian mineral layers offer tempting clues

Clay minerals such as montmorillonite and other smectites have been previously detected in layered outcrops in and around the Martian outflow channel Mawrth Vallis. Wray et al. additionally identify kaolinite and oxide minerals such as hematite in the Mawrth Vallis outcrops and find that these diverse minerals occur in distinct stratigraphic horizons, implying either that they formed over time under different environmental conditions or that they have distinctly different sediment sources. The authors observe that this pattern of layers occurs on both sides of the outflow channel and on its floor, with aluminum-rich clay-bea
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Contact: Peter Weiss pweiss@agu.org 202-777-7507 American Geophysical Union Source:Eurekalert

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