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We present a simulation of the New Zealand Southern Alps icefield at the Last Glacial Maximum (LGM, c. 30,000–20,000 calendar years ago (ka)) in an attempt to constrain the climate of that period. We use a 500 m-resolution ice-sheet model parameterised using empirical glaciological, climatological and geological data specific to the model domain to simulate the entire Southern Alps icefield. We find that an LGM cooling of at least 6–6.5 °C is necessary to bring about valley glaciers that extend beyond the mountains. However, climate–topography thresholds related to the elevation and hypsometry of individual catchments control the gradient of the rate of glacier expansion in the domain, and in order to remain within geologically reconstructed LGM limits we find that the LGM cooling was most likely associated with a precipitation regime up to 25% drier than today. Wetter-than-present scenarios give rise to equilibrium line depressions and ice extents that are incompatible with empirical evidence. These results perhaps indicate that either the westerly air masses affecting New Zealand during the LGM were drier than today, or that they were weaker or zonally displaced with respect to present.

Retreat of the Last Glacial Maximum (LGM) Antarctic ice sheet is thought to have been initiated by changes in ocean heat and eustatic sea level propagated from the Northern Hemisphere (NH) as northern ice sheets melted under rising atmospheric temperatures. The extent to which spatial variability in ice dynamics may have modulated the resultant pattern and timing of decay of the Antarctic ice sheet has so far received little attention, however, despite the growing recognition that dynamic effects account for a sizeable proportion of mass-balance changes observed in modern ice sheets. Here we use a 5-km resolution whole-continent numerical ice-sheet model to assess whether differences in the mechanisms governing ice sheet flow could account for discrepancies between geochronological studies in different parts of the continent. We first simulate the geometry and flow characteristics of an equilibrium LGM ice sheet, using pan-Antarctic terrestrial and marine geological data for constraint, then perturb the system with sea level and ocean heat flux increases to investigate ice-sheet vulnerability. Our results identify that fast-flowing glaciers in the eastern Weddell Sea, the Amundsen Sea, central Ross Sea, and in the Amery Trough respond most rapidly to ocean forcings, in agreement with empirical data. Most significantly, we find that although ocean warming and sea-level rise bring about mainly localized glacier acceleration, concomitant drawdown of ice from neighboring areas leads to widespread thinning of entire glacier catchments—a discovery that has important ramifications for the dynamic changes presently being observed in modern ice sheets.

Due to the difficulty of field characterization, one is often forced to employ hydrological models in order to determine estimates of aquifer recharge. A Geographical Information System (GIS) and Digital Elevation Model (DEM) may provide the basic support for such hydrological models. Unfortunately, despite the availability of these tools, the values of many parameters within distributed models remain uncertain for application to real world problems. Using the Bisagno basin (100 km2) in the Liguria region of Italy, the role of model parameter uncertainty on estimates of recharge to the Bisagno Aquifer is demonstrated. Uncertainty estimation is achieved through Monte Carlo simulations with the aid of the Generalised Likelihood Uncertainty Estimation procedure of Beven & Binley (1992).