Learn More
24. The Claremont gap in the NE varve chronology separated varves from the lower (NE varves 2701 through 6352) and upper (NE varves 6601 through 7750) Con-necticut River valley (Glacial Lake Hitchcock). Ridge et al. (22) linked the two sequences (lower NE varve 6012 ϭ upper NE varve 6601) to correct this gap. The Hudson Valley gap (NE varves 5600 through(More)
We show that the escape of hydrogen from early Earth's atmosphere likely occurred at rates slower by two orders of magnitude than previously thought. The balance between slow hydrogen escape and volcanic outgassing could have maintained a hydrogen mixing ratio of more than 30%. The production of prebiotic organic compounds in such an atmosphere would have(More)
Some of the global warming from anthropogenic greenhouse gases is offset by increased reflection of solar radiation by clouds with smaller droplets that form in air polluted with aerosol particles that serve as cloud condensation nuclei. The resulting cooling tendency, termed the indirect aerosol forcing, is thought to be comparable in magnitude to the(More)
Homogeneous freezing of nitric acid hydrate particles can produce a polar freezing belt in either hemisphere that can cause denitrification. Computed denitrification profiles for one Antarctic and two Arctic cold winters are presented. The vertical range over which denitrification occurs is normally quite deep in the Antarctic but limited in the Arctic. A 4(More)
In situ measurements of the relative humidity with respect to ice (RHi) and of nitric acid (HNO3) were made in both natural and contrail cirrus clouds in the upper troposphere. At temperatures lower than 202 kelvin, RHi values show a sharp increase to average values of over 130% in both cloud types. These enhanced RHi values are attributed to the presence(More)
The martian valley networks formed near the end of the period of heavy bombardment of the inner solar system, about 3.5 billion years ago. The largest impacts produced global blankets of very hot ejecta, ranging in thickness from meters to hundreds of meters. Our simulations indicated that the ejecta warmed the surface, keeping it above the freezing point(More)
Center for Atmospheric Research (NCAR) mesoscale dynamical model and used to simulated cirrus clouds during the First ISCCpCa) Regional Experiment (FIRE) project. One of our goals in performing one-dimensional studies is to develop the microphysics for these three-dimensional simulations. However, since the microphysics itself is computationally very(More)