Ashton Robinson

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Using a new approach to force an ice sheet model, we performed an ensemble of simulations of the Greenland Ice Sheet evolution during the last two glacial cycles, with emphasis on the Eemian Interglacial. This ensemble was generated by perturbing four key parameters in the coupled regional climate-ice sheet model and by introducing additional uncertainty in(More)
In this paper, we propose a new sub-grid scale parameterization for the ice discharge into the ocean through outlet glaciers and inspect the role of different observational and palaeo constraints for the choice of an optimal set of model parameters. This parameterization was introduced into the polythermal ice-sheet model SICOPOLIS, which is coupled to the(More)
We present optical spectropolarimetry of the nuclei of 36 Seyfert 1 galaxies, obtained with the William Herschel and the Anglo–Australian Telescopes from 1996 to 1999. In 20 of these, the optical emission from the active nucleus is intrinsically polarized. We have measured a significant level of polarization in a further 7 objects but these may be heavily(More)
We present detailed scattering models confirming that distinctive variations in polarization across the broad Hα line, which are observed in a significant fraction of Seyfert 1 galaxies, can be understood in terms of a rotating line-emitting disc surrounded by a co-planar scattering region (the equatorial scattering region). The predicted polarization(More)
The findings of a nine-orbit calibration plan carried out duringHST Cycle 15, to fully determine the NICMOS camera 2 (2.0 μm) polarization calibration to high accuracy, are reported. Recently Ueta et al. and Batcheldor et al. have suggested that NICMOS possesses a residual instrumental polarization at a level of 1.2%–1.5%. This would completely inhibit the(More)
The impact of El Niño-Southern Oscillation (ENSO) on United States tornadoes has been a controversial topic in the last 15 years. Widely varied and contradicting conclusions exist regarding the topic, especially when attempting to correlate shifts in location of tornadoes to ENSO phase. For instance, Hagemeyer (1998) noted a tendency toward stronger, more(More)
The halfwidth of the P(16) CO2 laser transition has been measured over a temperature range from 373 to 620 K at pressures varying from 20 to 100 Torr. A Voigt profile line shape was fitted to the experimental absorption coefficient to determine the variation of halfwidth with temperature. The pressure broadened halfwidth varied as T(-0.56) over this(More)