Katherine Klink, Associate Fellow

Modeling Regional Climate-Vegetation Interactions During the Holocene in the Upper Great Lakes Region

Climate and vegetation in the Upper Great Lakes region (Minnesota, Wisconsin, and Michigan) have been influenced not only by continental-scale movement of air masses but also by substrate types and regional features such as the Great Lakes and the prairie-forest border. For a better understanding of Holocene climate-vegetation interactions in the Upper Great Lakes region, regional models of climate (RegCM2) and flora/vegetation (STASH and FORSKA) were used to evaluate land surface-atmosphere interactions for the present day and for 11,000 (11k), 6k, and 3k years ago. Output from these models was linked to a pollen dispersion model (POLLSCAPE), and the results compared to observed fossil pollen from a high-quality, welldated regional pollen database. The similarity of predicted and observed pollen assemblages were used to evaluate climate predictions. When disagreements occurred, their patterns in space and time helped to identify sources of error, and sensitivity studies continued to be used to evaluate the modeling strategies.

Another project involves the temporal and spatial characteristics of surface winds. Although the wind field is an important feature of the surface climate and is routinely reported by weather observers, little effort has been devoted to compiling a data set that describes these characteristics. This research focuses on temporal analyses of mean wind speeds and on measures of dispersion (such as variance and interquartile ranges). It involves using wind observations in the upper Midwest to evaluate the spatial and temporal variability in wind speed patterns. Some stations (e.g., LaCrosse, Wisconsin) show distinct periods of higher and lower wind speeds over the period, while other stations (e.g., Rochester, Minnesota) have a more or less monotonic upward trend in speed. There also is evidence that the statistical distribution of wind speeds observed at several sites has changed over time, and this has implications for wind energy generation.