Summer dryness due to an increase of atmospheric CO2 concentration

To investigate the hydrologic changes of climate in response to an increase of CO₂-concentration in the atmosphere, the results from numerical experiments with three climate models are analyzed and compared with each other. All three models consist of an atmospheric general circulation model and a simple mixed layer ocean with a horizontally uniform heat capacity. The first model has a limited computational domain and simple geography with a flat land surface. The second model has a global computational domain with realistic geography. The third model is identical to the second model except that it has a higher computational resolution. In each numerical experiment, the CO₂-induced change of climate is evaluated based upon a comparison between the two climates of a model with normal and four times the normal concentration of carbon dioxide in air. It is noted that the zonal mean value of soil moisture in summer reduces significantly in two separate zones of middle and high latitudes in response to the increase of the CO₂-concentration in air. This CO₂-induced summer dryness results not only from the earlier ending of the snowmelt season, but also from the earlier occurrence of the spring to summer reduction in rainfall rate. The former effect is particularly important in high latitudes, whereas the latter effect becomes important in middle latitudes. Other statistically significant changes include large increases in both soil moisture and runoff rate in high latitudes of a model during most of the annual cycle with the exception of the summer season. The penetration of moisture-rich, warm air into high latitudes is responsible for these increases.     

SO2 from episode 48A eruption,Hawaii: Sulfur dioxide emissions from the episode 48A East Rift Zone eruption of Kilauea volcano,Hawaii

An SO₂ flux of 1170±400 (1) tonnes per day was measured with a correlation spectrometer (COSPEC) in October and November 1986 from the continuous, nonfountaining, basaltic East Rift Zone eruption (episode 48A) of Kilauea volcano. This flux is 5–27 times less than those of highfountaining episodes, 3–5 times greater than those of contemporaneous summit emissions or interphase Pu'u O'o emissions, and 1.3–2 times the emissions from Pu'u O'o alone during 48A. Calculations based on the SO₂ emission rate resulted in a magma supply rate of 0.44 million m³ per day and a 0.042 wt% sulfur loss from the magma upon eruption. Both of these calculated parameters agree with determinations made previously by other methods.     

Equilibrium response of thermohaline circulation to large changes in atmospheric CO2 concentration

This study evaluates the equilibrium response of a coupled ocean–atmosphere model to the doubling, quadrupling, and halving of CO₂ concentration in the atmosphere. Special emphasis in the study is placed upon the response of the thermohaline circulation in the Atlantic Ocean to the changes in CO₂ concentration of the atmosphere. The simulated intensity of the thermohaline circulation (THC) is similar among three quasi-equilibrium states with the standard, double the standard, and quadruple the standard amounts of CO₂ concentration in the atmosphere. When the model atmosphere has half the standard concentration of CO₂, however, the THC is very weak and shallow in the Atlantic Ocean. Below a depth of 3 km, the model oceans maintain very thick layer of cold bottom water with temperature close to –2 °C, preventing the deeper penetration of the THC in the Atlantic Ocean. In the Circumpolar Ocean of the Southern Hemisphere, sea ice extends beyond the Antarctic Polar front, almost entirely covering the regions of deepwater ventilation. In addition to the active mode of the THC, there exists another stable mode of the THC for the standard, possibly double the standard (not yet confirmed), and quadruple the standard concentration of atmospheric carbon dioxide. This second mode is characterized by the weak, reverse overturning circulation over the entire Atlantic basin, and has no ventilation of the entire subsurface water in the North Atlantic Ocean. At one half the standard CO₂ concentration, however, the intensity of the first mode is so weak that it is not certain whether there are two distinct stable modes or not. The paleoceanographic implications of the results obtained here are discussed as they relate to the signatures of the Cenozoic changes in the oceans.An erratum to this article can be found at