LAKE BONNEVILLE SPIT ORIENTATION AND PLACEMENT OF THE PLEISTOCENE JET STREAM

During the last glacial maximum (LGM), the jet stream over North America is believed to have been split into two branches by the continental ice sheet. While the precise location of the southern branch of the jet stream is suggested by general circulation models, field evidence to validate model output has been elusive. As part of a larger project to use geomorphic features to understand continental climates of the Pleistocene of North America, the geomorphology of small mountain ranges that were islands in the middle of Lake Bonneville of the eastern Great Basin have been examined in detail. Spits of the Bonneville and uppermost Provo levels in these mountain ranges are oriented in a persistent southerly direction. Spit orientation is best explained as the result of strong northerly winds caused by the atmospheric high pressure cell of the continental ice sheet and passage of low pressure, extratropical storms south of Lake Bonneville. The continental divide may have played a role in channeling these winds in a southerly direction. If this hypothesis is correct, the North American jet stream tracked south of Lake Bonneville as recently as 14,500 radiocarbon years before the present, well past the height of the LGM.