Numerical computations are performed with the three-dimensional polythermal ice-sheet model SICOPOLIS in order to investigate the possible impact of a greenhouse-gas-induced climate change on the Greenland ice sheet. The assumed increase of the mean annual air temperature above the ice covers a range from T = 1 C to 12 C, and several parameterizations for the snowfall and the surface melting ar...

We explore potential changes in Greenland ice sheet form and flow associated with increasing ice temperatures and relaxing effective ice viscosities. We define "thermal-viscous collapse" as a transition from the polythermal ice sheet temperature distribution characteristic of the Holocene to temperate ice at the pressure melting point and associated lower viscosities. The conceptual model of th...

Palaeo data suggest that Greenland must have been largely ice free during Marine Isotope Stage 11 (MIS-11). However, regional summer insolation anomalies were modest during this time compared to MIS-5e, when the Greenland ice sheet likely lost less volume. Thus it remains unclear how such conditions led to an almost complete disappearance of the ice sheet. Here we use transient climate-ice shee...

[1] We present glaciological and climatological characteristics of Hercules Dome, Antarctica (86 S, 105 W), which demonstrate its potential as a deep ice core site. Annual layering in dD ratios from a 72 m ice core collected by the US-ITASE 2002 traverse indicate accumulation rates of 0.16–0.20 m/yr ice equivalent over the last 300 years. Age control from stratigraphy seen in the radio-echo sou...

We studied electrostatic charging of ice films induced by the impact of 1−200-keV Ar+ ions and their subsequent discharging postirradiation. We derived the positive surface electrostatic potential from the kinetic energy of sputtered molecular ions and with a Kelvin probe. Measurements were performed as a function of film thickness, temperature, and ion energy. Charging requires that the projec...

The data obtained from field and geothermometric studies and also the REE composition of fluorites associated with lead mineralization at the Kamar-Mehdi mine are compatible with a structurally controlled, fissure filling, epigenetic, hydrothermal origin. Homogenization and last ice melting temperatures for primary fluid inclusions trapped in fluorite crystals indicate that the mineralizati...

[1] Key steps leading to the uptake of trace gases into atmospheric cloud ice particles include gas phase diffusion of trace gas molecules toward growing ice crystals and the kinetics of molecular interactions at the ice surfaces. In the case of nitric acid, laboratory studies and airborne field observations indicate uptake in growing ice films and cirrus ice particles above the thermodynamic s...