AGU Journal Highlights -- Aug. 14, 2007

Authors: Kevin E. Trenberth and Aiguo Dai: National Center for Atmospheric Research, Boulder Colorado, U.S.A.

Source: Geophysical Research Letters (GRL) paper 10.1029/2007GL030524, 2007

9. Stomatal conductance and climate sensitivity to carbon dioxide

In order to fix carbon, plants transpire water and take up atmospheric carbon dioxide (CO₂) through stomata, which are small openings in leaves. The density of stomata on a leaf indicates the abundance of carbon dioxide in the atmosphere—high densities mean that CO₂ is scarce, while low densities mean that CO₂ is plentiful. This effect has previously been used to reconstruct CO₂ concentrations in the Earth's past. Now, by including the effect in a coupled vegetation-climate model, Kleidon finds that doubling the abundance of CO₂ in the atmosphere could increase land temperatures by 2.7ºC to 3.2ºC, depending on whether stomata adapt optimally or not at all. The model incorporates the assumption that stomata function optimally to maximize growth. If such stomata functioning is not assumed, climate model predictions of the expected rise in CO₂ will generally underestimate vegetative cover

Title: Optimized stomatal conductance and the climate sensitivity to carbon dioxide

Authors: A. Kleidon: Max-Plank-Institut für Biogeochemie, Jena, Germany.

Source: Geophysical Research Letters (GRL) paper 10.1029/2007GL030342, 2007

10. Indian Ocean response to anomalous conditions in 2006

The thermal structure of the equatorial Indian Ocean is characterized by warmer temperatures in the east and cooler temperatures in the west. During certain years, this pattern switches to anomalous conditions known as the Indian Ocean Dipole; one such dipole event occurred in 2006. From satellite observations over the oceans from that time, Vinayachandran et al. find that the eastern Indian Ocean not only exhibited colder sea surface temperatures, but also showed lower sea levels and higher chlorophyll content than normal. By contrast, the western Indian ocean was marked by warmer sea surface temperatures, higher sea level, and a steep, deeper thermocline. The authors model this event using an ocean general circulation model forced with satellite-derived wind data. Their reproductions match well with the actual event, and reveal that air-sea heat fluxes initiated the cold sea surface temperatures in the east, which were sustained by ocean dynamics. Similar fluxes fueled the warm surface temperatures in the west. The event reverted back to initial conditions in the fall of 2006.

Title: Indian Ocean response to anomalous conditions in 2006

Authors: P. N. Vinayachandran, Jaison Kurian, and C. P. Neema: Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore, India.

Source: Geophysical Research Letters (GRL) paper 10.1029/2007GL030194, 2007

11. Coastal notches and seismic uplift rates in Greece