Retrospective simulation of lake-level rise in Lake Bonney based on recent 21-year record: indication of recent climate change in the McMurdo Dry Valleys, Antarctica

The physical and chemical characteristics of Lake Bonney, a permanently ice-covered closed basin lake in Taylor Valley, Antarctica are influenced significantly by local climate. The rising lake-levels of the past thirty years indicate a recent change in the local climate. We explored the significance of twentieth century changes in lake-level as a climate-change indicator by using a hydrologic model for the basin and a Monte Carlo simulation based on the variability in the available 30 yrs of hydrologic record. We compared the lake-level in the retrospective simulations with a measurement surveyed by Robert Scott's party in 1903. All the retrospective simulations based on the observed inflows yielded estimates that the lake was dry in 1903. It was necessary to remove 6 yrs from the observed 21-yr record for the retrospective simulation to match the measured 1903 lake-level for 50% of the simulations. From these analyses, we conclude that the period from 1969 to the present has had greater availability of solar radiation for meltwater generation, possibly brought about by changing cloud-cover patterns and coupled with a gradual warming trend. A third simulation indicated that an annual increase in inflow of about 3% between 1903 and 1973 would be required to match the 1903 measurement.