A more thorough understanding of regional to hemispheric hydroclimate variability and associated climate patterns is needed in order to validate climate models and project future conditions. In this study, two annually laminated (varved) sediment records spanning the last millennium were analyzed from Rhode Island and New York. Lamination thickness time series from the two locations are significantly correlated to hydroclimate indicators over the period of instrument overlap, demonstrating their usefulness in reconstructing past conditions. Both records are correlated to climate teleconnection indices, most strongly the Pacific/North American (PNA) pattern, suggesting regional to hemispheric influences on hydroclimate. Such a linkage is interpreted to be due to tropospheric circulation patterns in which positive PNA periods are associated with meridional circulation, leading to the dominance of southern moist air masses in the Northeast United States. Alternatively, the zonal flow over North America associated with negative PNA periods produces dominant dry continental air masses over the region. A composite record from the two locations reveals variability of hydroclimate and atmospheric circulation over the late Holocene and shows similarities to previously published reconstructions of the circumpolar vortex and of the Aleutian Low-pressure system, supporting the hypothesized PNA linkage. The record is correlated to continental-scale droughts, many of which have been reconstructed in the American Southwest. These results demonstrate the PNA’s influence on hydroclimate over North America, and suggest that this teleconnected pattern may have a significant role in continental drought dynamics.
With growing use of numerical models to forecast lake conditions under future climates and other stressors, paleo-events in the history of the Great Lakes have greater potential for relevance. Past events and history may extend records of observations, provide estimates of the sensitivity of the lake system to stressing conditions, and contribute scenarios for model validation. Here we describe four examples that hold promise for improving understanding of the present and future Great Lakes: 1) using an event of lake closure to derive climate-hydrology sensitivity, 2) extending the record of lake-level history by examining beach ridge sequences, 3) investigating sedimentary black bands to indicate past anoxia at the lakebed in deep basins, and 4) deriving evidence of lake process teleconnections with atmospheric circulation.
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