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To predict the future contributions of the Antarctic ice sheets to sea-level rise, numerical models use reconstructions of past ice-sheet retreat after the Last Glacial Maximum to tune model parameters.sup.1. Reconstructions of the West Antarctic Ice Sheet have assumed that it retreated progressively throughout the Holocene epoch (the past 11,500 years or so).sup.2-4. Here we show, however, that over this period the grounding line of the West Antarctic Ice Sheet (which marks the point at which it is no longer in contact with the ground and becomes a floating ice shelf) retreated several hundred kilometres inland of today's grounding line, before isostatic rebound caused it to re-advance to its present position. Our evidence includes, first, radiocarbon dating of sediment cores recovered from beneath the ice streams of the Ross Sea sector, indicating widespread Holocene marine exposure; and second, ice-penetrating radar observations of englacial structure in the Weddell Sea sector, indicating ice-shelf grounding. We explore the implications of these findings with an ice-sheet model. Modelled re-advance of the grounding line in the Holocene requires ice-shelf grounding caused by isostatic rebound. Our findings overturn the assumption of progressive retreat of the grounding line during the Holocene in West Antarctica, and corroborate previous suggestions of ice-sheet re-advance.sup.5. Rebound-driven stabilizing processes were apparently able to halt and reverse climate-initiated ice loss. Whether these processes can reverse present-day ice loss.sup.6 on millennial timescales will depend on bedrock topography and mantle viscosity--parameters that are difficult to measure and to incorporate into ice-sheet models.Radiocarbon dating of sediment cores and ice-penetrating radar observations are used to demonstrate that the West Antarctic Ice Sheet has not retreated progressively during the Holocene epoch, but has instead showed periods of retreat and re-advance., Author(s): J. Kingslake [sup.1] , R. P. Scherer [sup.2] , T. Albrecht [sup.3] , J. Coenen [sup.2] , R. D. Powell [sup.2] , R. Reese [sup.3] , N. D. Stansell [...]

Emerging monitoring methods will allow scientists to keep an eye on many more volcanoes. Emerging monitoring methods will allow scientists to keep an eye on many more volcanoes., Author(s): Alexandra Witze Author Affiliations: How AI and satellites could help predict volcanic eruptions Agung volcano on the Indonesian island of Bali erupts in November 2017. [see PDF for image] [...]

Bird migration is influenced by weather, making it hard to predict when birds will pass through a particular place on their route. A model that forecasts bird migrations has been developed using radar data and weather information.The development of a system to predict bird-migration movements., Author(s): Mary AbrahamAuthor Affiliations:Bird forecasting by radar Credit: P. Choui/Getty [see PDF for image]A male Baltimore Oriole flaps his wings as he takes flight from a branchRelated [...]