East central North America climates during marine isotope stages 3-5

Long-term, high-resolution stalagmite carbon and oxygen isotope records from eastern North America (ENA) provide a midlatitude history of relative changes in moisture availability and climate states during the last interglacial and glacial inception (127.7 to 41.6 ka before present). The West Virginia carbon record shows low-amplitude variability at orbital time scales, superimposed on a long-term asymmetric pattern similar to global sea level changes. Relative moisture availability peaked at ~114 ka, and following a brief dry interval at ~96 ka, moisture availability gradually decreased. The almost linear change in moisture availability over ENA may reflect gradual changes in midlatitude zonal circulation as the polar cell and Laurentide Ice Sheet expanded or decreased. In contrast, our oxygen record is precession modulated and in phase with spring insolation, perhaps due to changes in precipitation seasonality. The separate pacings by eccentricity (carbon) and precession (oxygen) expose an underlying complexity that will be a challenge to explain.