Km3 Of Ice Research Articles

Research into the Hansbreen, a tidewater glacier in Spitsbergen

Abstract The data presented are the results of Soviet‐Polish field studies made on Hansbreen in 1989. Data from geodetic surveys show that between 1936 and 1989 the glacier retreated approximately 900 m and thinned in its lower part by an average of 50 m. Over this same period its volume shrank by 1.25 km3 of ice, i.e., by 0.46 m/ yr of water equivalent. The annual mass balance of the glacier in 1988–1989 was ‐540 g/cm2; of this ‐350 g/cm2, or 65% of the total, was lost by iceberg calving. Thus in 1988–1989 the glacier lost 30.55 million m3 of water, 20 million m3 of which was by iceberg calving. In the year of observations the equilibrium line lay at a height of 325 m and the accumulation zone accounted for 0.53 of the total area. According to data from surface radio echo soundings 75% of the area of the glacier bed lies below sea level, at depths of up to 102 m. Three overdeepened basins were detected in the glacier bed; the intervening bars might act as stabilization levels in the course of retreat. Th...

Evidence from Antarctic ice cores for recent increases in snow accumulation

LARGE uncertainties exist in the present knowledge of the mass budget of the Antarctic ice sheet, because of a lack of data on the rates of both ice outflow and snow accumulation1. Present estimates indicate that both the outflow and the net accumulation are approximately equal to 2,000 km3 of ice per year (equivalent to about 6 mm of sea level)2. The temporal variation of accumulation rate is central to determinations of the mass budget, because accumulation can change rapidly in response to short-term climate variations, whereas ice flow varies only on longer timescales. Here we present time series showing changes in the net rate of snow accumulation since 1806 along a 700-km segment of East Antarctica. The accumulation record was derived from the thicknesses of annual layers in ice cores, deduced from seasonal variations in oxygen isotope ratio and in ice-crust stratigraphy. We find a significant increase in the accumulation rate following a minimum around 1960, leading to recent rates that are about 20% above the long-term mean. If this recent increase is widespread, as suggested by shorter-term accumulation data from across a large part of Antarctica, the positive imbalance (5–25% of the mass input) shown in recent studies of the ice sheet's mass budget1 may have existed only since the late 1960s. We estimate that this increase in accumulation rate should contribute to a lowering of sea level of 1.0–1.2 mm per year.

The seasonal and global behavior of water vapor in the Mars atmosphere: Complete global results of the Viking Atmospheric Water Detector Experiment

The water vapor content of the Mars atmosphere was measured from the Viking Orbiter Mars Atmospheric Water Detectors (MAWD) for a period of more than 1 Martian year, from June 1976 through April 1979. Results are presented in the form of global maps of column abundance for 24 periods throughout each Mars year. The data reduction incorporates spatial and seasonal variations in surface pressure and supplements earlier published versions of less complete data. Column abundances vary between 0 and about 100 precipitable microns (pr μm), depending on location and season, while the entire global abundance varies seasonally between an equivalent of about 1 and 2 km3 of ice. The first appearance of vapor at nonpolar latitudes as northern summer approaches and the drop in abundance at mid‐latitudes as summer ends both strongly imply the existence of a seasonal reservoir for water within the regolith. There appear to be no net annual sources away from the poles that contribute significant amounts of water. However, the strong annual gradient of vapor from north to south implies a net annual flow of vapor toward the south. This southward flow may be balanced by a northward flow during the global dust storms, by transport in the form of clouds or adsorbed onto dust grains, or during other years. The perenially cold nature of the south polar residual cap, along with the relatively large summertime vapor abundances over the cap, implies a net annual condensation of vapor onto the cap. Comparison with earlier (Earth‐based) observations of vapor in the south during the local summer indicates that all of the seasonal CO2 cap may sublime away in some years to reveal the water ice cap which must lie underneath, with corresponding large southern summer vapor abundances. The global distribution of the annual average abundance of vapor correlates well with Martian topography, as might be expected for a uniform constant atmospheric mixing ratio. If this topographic effect is divided out, the resulting residual map correlates well with maps of surface albedo and thermal inertia; this correlation may be related to the control exerted by the surface and subsurface temperatures on the adsorption/desorption process and on the atmospheric temperature profile and, hence, the vapor holding capacity of the atmosphere.