Mountain glaciers respond to climate change by rapidly advancing or receding as temperatures vary, and this change in glacier extent controls hydrology, sediment transport, and deposition in rivers downstream.
The sedimentary record in glaciated catchments therefore represents an important archive with which to unravel past climate change. However, unlike rivers, whose flow is controlled entirely by land surface topography, glaciers are able to flow uphill and across ridgelines -- a process called "transfluence." Glacier advance and recession can result in drainage capture by transfluent ice flow, and so change catchment drainage areas and hydrological budgets.
Ann Rowan and colleagues use a 3-D glacier model of ice flow during the last glaciation in adjacent catchments in the Southern Alps of New Zealand to find that glacial-drainage capture is a more important control on hydrology and the sedimentary record than climate change alone.
These results from New Zealand demonstrate how scientists can use the sedimentary record to investigate past climate change both in this mid-latitude Southern Hemisphere location and in glaciated settings worldwide.
Paper: Ann V. Rowan et al., doi: 10.1130/G33829.1