  The RICE experiment seeks observation of ultra-high energy (UHE; >100 PeV)
neutrinos interacting in Antarctic ice, by measurement of the radiowavelength
Cherenkov radiation resulting from the collision of a neutrino with an ice
molecule. RICE was initiated in 1999 as a first-generation prototype for an
eventual, large-scale in-ice UHE neutrino detector. Herein, we present updated
limits on the diffuse UHE neutrino flux, based on twelve years of data taken
between 1999 and 2010. We find no convincing neutrino candidates, resulting in
95% confidence-level model-dependent limits on the flux which improve on our
previous (2006) results by a factor of two. We also report on ice properties'
studies, including observation of radiowave reflections from layers internal to
the ice sheet. We observe correlations of these reflections with the local ice
flow direction, and also qualitatively verify the expected reduction in radio
frequency ice transparency with increasing depth/temperature. A new
experimental initiative (the Askaryan Radio Array, ARA) commenced at South Pole
in 2010-11 will improve the RICE sensitivity (per unit time) by approximately
two orders of magnitude.
