Lakes beneath the ice sheet: The occurrence, analysis, and future exploration of Lake Vostok and other Antarctic subglacial lakes

Airborne geophysics has been used to identify more than 100 lakes beneath the ice sheets of Antarctica. The largest, Lake Vostok, is more than 250 km in length and 1 km deep. Subglacial lakes occur because the ice base is kept warm by geothermal heating, and generated meltwater collects in topographic hollows. For lake water to be in equilibrium with the ice sheet, its roof must slope ten times more than the ice sheet surface. This slope causes differential temperatures and melting/freezing rates across the lake ceiling, which excites water circulation. The exploration of subglacial lakes has two goals: to find and understand the life that may inhabit these unique environments and to measure the climate records that occur in sediments on lake floors. The technological developments required for in situ measurements mean, however, that direct studies of subglacial lakes may take several years to happen

Geometric evolution and ice dynamics during a surge of Bakaninbreen, Svalbard

AbstractBakaninbreen, Svalbard, started surging in 1985 and developed a steep surge front where fast-moving ice impinged on stagnant non-surging ice. This front, which was 20- 25 m high in 1985, became a steep and heavily crevassed feature about 60 m high. The surge continued through 1986-95. Annual surge-front propagation rate was 1.0 1.8 km a−1during 1985-89; this rate dropped considerably during 1989 95 and the front became less steep. Front propagation occurred largely by longitudinal compression and vertical extension of the ice and the effects of over-riding appear minor. Ice velocities were slower than the average propagation rate of the front. The surge affected Bakaninbreen in four zones: (1)Upper regionwhere extensive flow, fast propagation rates and negative vertical strain occurred, resulting in widespread crevassing and stranded blocks tens of metres above the post-surge ice surface, (2)Mid-glacierregion where initial strong compression was associated with ice thickening which started before the arrivai of the surge front. Horizontal strain rates were very low but vertical strain rates were tip to 300 mmd−1. As (he front passed, the horizontal velocity increased and about 500 m behind it became extensive. Negative vertical strain and ice down-draw occurred as ice velocities dropped, (3)Surge frontwhere ice velocity was high but vertical strain remained positive associated with compression. (4)Lower regionbelow the iront where only compression occurred, resulting in the formation of a fore bulge, a thickening of the ice of up to 50 m above pre-surge levels. The fore bulge affected the whole 1.7 km below the, now halted, surge front. The glacier has not advanced, Bakaninbreen’s surge was characterized by a long active phase, approximately 10 years, low ice velocities and low basal shear stresses compared to glaciers in lower latitudes, and an indistinct surge termination.</jats:p

Conflicts of interest in the use of Antarctica

The International Geophysical Year of 1957–58 demonstrated the effective use of the Antarctic for peaceful international scientific activity, and the Antarctic Treaty of 1961 acknowledges the important contribution of science. The pre-eminent position accorded to science has been vindicated: 30 years of intensive research have shown the intimate connections and controlling influences of Antarctica on the principal environmental systems of planet Earth (climate, ocean circulation and sea level

The heat budget of the Ross drainage basin

Integration of the thermodynamic equation over an entire drainage basin yields a fairly simple expression for the steady-state heat balance. This stems from the fact that dissipative heating can be calculated directly from the release of gravitational energy. When mass balance, surface temperature and geothermal input are known, the mean ice temperature at the grounding line can be obtained as a residual. The procedure is applied to the drainage basin feeding the Ross Ice Shelf. The resulting mean outlet temperature is -16.2 oC. The heating rates making the balance turn out to be (in 0.0001 K/yr): dissipation 8.2, advective flux divergence -13.5 and geothermal heating 5.3. The method also reveals how the mean outlet temperature depends on mass balance, surface elevation, etc

Regime of the Filchner-Ronne Ice Shelves, Antarctica

Seismic, radio-echo, TWERLE balloon and oceanographic data of the Filchner-Ronne ice shelves are analysed. A large thin area in the central Ronne Ice Shelf is found to differ from the morphology of the Ross and Filchner ice shelves. This area is partly filled by basal saline ice, which can be attributed to regional regelation caused by oceanic circulation