Last Interglacial (MIS 5e) and Holocene paleohydrology and paleovegetation of midcontinental North America from Gulf of Mexico sediments

Abstract

Marine Isotope Stage (MIS) 5e experienced slightly higher insolation and lower global ice volume compared to the pre-industrial climate. We examined how these slight changes in global climate state during the MIS 5e influenced hydrologic and vegetation conditions in the Mississippi River Basin (MRB) in North America (NA) compared to the Holocene. To do this, we reconstructed paleohydrology and paleovegetation conditions during the last 150 ka using leaf waxes (n-alkanes) andtheir carbon (δ13Calk) and hydrogen (δ2Halk) isotopic compositions preserved in ODP 625B core from the northwestern Gulf of Mexico (GOM) near the MRB discharge area. In the early MIS 5e, climate may have been slightly wetter than the Holocene based on δ2Halk values that indicate higher warm and moist air mass contributions from the GOM and Atlantic. This is related to southern expansion of the Atlantic Warm Pool and northward shift of the ITCZ with increased warming that extended warm air masses from the GOM to the MRB resulting in a northward shift of the jet stream and precipitation belt over the NA continent. The climate may have become drier towards late MIS 5e with C4 grassland expansion, which were sustained through the MIS 5c. We speculate that this may be due to prolonged warm and dry climate conditions from early to mid MIS 5. There were notable increases in leaf wax export from western dry grasslands during deglaciation (13.5 ka) and