Interactions between ice and ocean observed with phase-sensitive radar near an Antarctic ice-shelf grounding line

摘要: Precise measurements of basal melting have been made at a series 14 sites lying within few kilometres the grounding line Ronne Ice Shelf, Antarctica, where ice thickness ranges from 1570 to 1940 m. The study was conducted over course 1 year and included detailed survey horizontal deformation, as well phase-sensitive radar vertical displacement both internal reflecting horizons ice-shelf base. Results surface show that long-term viscous strain rate is modulated tidal frequencies by (probably) elastic strains order 10−5 per metre elevation. similar modulation thinning/thickening shelf, with oscillations up centimetres in range. trends determined points moving flow are consistent steady-state profile. Vertical rates shelf were relative motion reflectors. At two observations sufficient discern effect bending about neutral 60% way down column. Coincident imply Poisson's ratio 0.5, this combined asymmetric gives rise observed thickness. number found be linear function depth. For an unexpected result. It can attributed presence significant shear stresses set close still adjusting flotation. Additional arising firn compaction upper layers shelf. additional assumption density only time since burial steady accumulation. With spatial temporal fluctuations accurately quantified it possible estimate base response. Differences between calculated reflector arise because melting. Derived melt ranged −0.11 ± 0.31 2.51 0.10 ma−1, mean 0.85 m a−1 standard deviation 0.69 a−1, showed no signs sub-annual variability. There obvious global correlation either or distance line, although tended decrease downstream along each flowlines studied. Previous estimates region obtained indirectly locally equilibrium broad range values. Only those lower end published directly measured reported here.