SMMR data over Antarctica have been statistically analysed for four different periods of 1 year (1981) and compared to geophysical data such as surface temperature, snow-accumulation rate and topography. The spatial variations of the microwave signature are stable with time. Although the ten channels are highly correlated, principal-component analysis reveals the importance of polarization and frequency. The difference between brightness temperatures at the two polarizations is found to be dependent on the atmospheric water-vapour fluxes over the ice sheet, which modify the temperature-accumulation ratio and therefore the snow stratification. The brightness-temperature gradient with frequency is related to the topography of the central plateau area. A more important subsidence over diverging areas could explain the different structure of the accumulated snow.

Annual total precipitation and the annual accumulation on the Greenland ice sheet are evaluated and presented in two maps. The maps are based on accumulation measurements of 251 pits and cores obtained from the upper accumulation zone and precipitation measurements made at 35 meteorological stations in the coastal region. To construct the accumulation map, the annual precipitation was split into solid and liquid precipitation components. Annual total precipitation exceeding 2500mmw.e. occurs on the southeastern tip of Greenland, while the minimum precipitation is estimated to occur on the northeastern slope of the ice sheet. The mean annual precipitation for all of Greenland is 340 mm w.e. The largest annual accumulation of about 1500 mm w.e. is found on the glaciers in the southeastern corner of Greenland, while the smallest accumulation is found on the northeastern slope of the ice sheet west of Danmarkshavn. The mean accumulation on the Greenland ice sheet is estimated at 310mmw.e. The regional difference in accumulation is examined with respect to the 850hPa(mbar) level circulation. The present surface topography is found to play an important role in determining regional accumulation on the ice sheet.

The Greenland ice sheet is modelled to simulate its extent and volume in warmer climates, and to find out whether the ice sheet would re-form on the ice-free bedrock under present climatic conditions. The ice-sheet model is a three-dimensional thermo-mechanical model with a fine-resolution grid. The bedrock surface beneath the ice sheet was mapped using radio-echo-sounding measurements by the Electromagnetic Institute, Copenhagen. The model experiments show that increased temperature will result in ice-margin retreat, but the ice sheet is relatively stable; it takes a temperature rise of at least 6 deg for the ice sheet to disappear completely, which indicates that the ice sheet probably survived the last interglacial. Furthermore, it appears that the Greenland ice sheet is not a mere relict ice mass from a previously colder climate but that the ice sheet will still re-form on the bare bedrock under the present, or even slightly warmer, climatic conditions.

Trapridge Glacier, Yukon Territory, Canada is a subpolar surge-type glacier. It last surged in the 1940s and is now in the late stages of quiescence. Since 1969, when the glacier was first surveyed, a large wave-like bulge has formed near the glacier terminus. Our surveys from 1969–89 show the profile evolution that has accompanied the formation and downflow propagation of this feature. Ice-temperature measurements taken in 1980–81 established that the bulge was forming at the boundary between thick warm-based ice lying up-glacier from the bulge, and thin cold-based ice lying down-glacier from it. The bulge is propagating at roughly 30 m a−1 and thick ice has now completely overridden the region once covered by thin cold-based ice that we instrumented in 1980–81. In 1987, and again in 1988, the geographical positions of the 1980 measurement sites were redrilled and instrumented with new thermistor cables. Comparison of the 1980–81 data with that from 1987–88 shows that this region of the glacier has undergone a dramatic change in geometry and thermal regime. Water penetration into surface crevasses has warmed the 15-m ice temperature by roughly 2°C. The zone of transition from warm- to cold-based ice is migrating down-glacier but at a slower rate than that of the bulge feature. The transition from warm-based to cold-based ice appears to cause a discontinuity in the flow that resembles a transition from flow over a sliding boundary to flow over an adhering boundary. The discontinuity in the flow field is associated with anomalies in the temperature field and appears to be the source region for an englacial structure formed from subglacial sediment. This structure was not present in 1980–81 and is thought to have the geometry of a thrust fault or recumbent fold.

Deep-drilling operations in glaciers require a fluid to maintain hydrostatic equilibrium and prevent closure due to plastic flow of the ice. Many past practices have employed various fluid mixtures using fuel oil as the base. The case for butyl acetate is presented here as an adequately dense and environmentally safe drilling fluid. Results from the 1990 drill season are highly favorable.

Salt-water ice was imaged in a 2Tesla, horizontal 310 mm bore NMR imaging system at 85 MHz. 50 mm diameter ice cylinders were placed in a temperature-controlled chamber in the NMR system and imaged at temperatures from −20° to 0°C. Paramagnetic Cu2SO4 at a low concentration was added to the solution, from which one ice sample was crystallized in order to decrease the NMR relaxation time of the entrapped brine in the ice cylinder and thereby speed up image acquisition. The Cu2SO4-spiked sample displayed what appears to be small brine pockets/channels which resemble larger drainage channels seen in thin plates of sea ice. The brine channels/pockets seen by NMR contracted as the temperature decreased. NMR imaging of salt ice appears to be an excellent way to visualize ice structure.