Persistence of coherence of ice-off dates for inland lakes across the Laurentian Great Lakes region

摘要

Ice phenologies, dates of ice-on and ice-off on lakes and rivers, provide information on climate change and variability. These long-term records indicate that lakes and rivers are sensitive to climatic change and variability. A symposium on ice phenologies of lakes as a climate indicator was held at the 27th Congress of the International Association of Theoretical and Applied Limnology in Dublin and published in the Verhandlungen (Magnuson et al. 2000b). Ice records have been especially useful because they can be long, over 150 years in length, and occur broadly around the Northern Hemisphere. In some areas, such as Finland (Kuusisto Elo 2000), Sweden (Weyhen-meyer et al. 2004), and the Great Lakes region of North America (Magnuson et al. 2005a, b), lakes with records of moderate length are common enough so that spatial patterns in dynamics can be analyzed. In some cases, records are sufficient to examine global, or at least intercontinental, trends (Magnuson et al. 2000a) and dynamics (Livingstone 2000, Magnuson et al. 2004). Our purpose here is to examine the spatial patterns of temporal coherence or synchrony in time series of ice-off dates between lakes in the Laurentian Great Lakes region. In particular, we (1) compare the coherence within and between four states and one province bordering the Great Lakes, (2) describe the persistence and decline of coherence between lakes with increasing latitudinal and longitudinal distances between them, and (3) suggest explanations for the observed pattern of coherence at multiple spatial scales. Coherence, as quantified here, is the shared variance between two time series. Discussions of coherent dynamics between lakes are reviewed in Magnuson Kratz (2000) and Magnuson et al. (2005b).