Supporting evidence from the New York drumlin field that elongate subglacial bedforms indicate fast ice flow

Although drumlins and other subglacial bedforms are well-studied features, controls on their formation and morphometry have remained elusive. Of current interest is the hypothesis that elongate bedforms (length:width ratios ≥ 10) indicate fast ice flow, and perhaps the location of past ice streams. This hypothesis is explored by analysing drumlins from the New York State drumlin field. A subset of 548 drumlins between Oneida Lake and Lake Ontario was digitized using 10-m grid cell digital elevation data. Because bedform elongation is greatest along the axis of a reconstructed lobe and increases down flowline, elongate bedforms are best explained by fast ice flow. The swath of elongate bedforms between lakes Ontario and Oneida, the boundaries of which do not coincide with topography, may signify the location of an ice stream during deglaciation.