Laurentian Great Lakes double-CO2 climate change hydrological impacts

Abstract

The Great Lakes Environmental Research Laboratory has developed conceptual daily models for simulating moisture storages in and runoff from the 121 watersheds draining into the Laurentian Great Lakes, over-lake precipitation into each lake, and the heat storages in and evaporation from each lake. We combine these components as net basin supplies for each lake to consider climate change scenarios developed from atmospheric general circulation models (GCMs). Recent scenarios of a doubling of atmospheric CO 2, available from the Goddard Institute for Space Studies, the Geophysical Fluid Dynamics Laboratory, and Oregon State University are considered by making changes in historical meteorological data similar to the changes observed in the GCMs, observing the impact of the changed data in the model outputs, and comparing outputs to model results using unchanged data, representing comparison to an unchanged atmosphere. This study indicates a 23 to 51% reduction in net basin supplies to all the Great Lakes; there is significant variation in the components of these supplies among the three GCMs. The basins various moisture storages become dryer and the lakes are warmer with associated hydrological impacts.

Present and future Laurentian Great Lakes hydroclimatic conditions as simulated by regional climate models with an emphasis on Lake Michigan-Huron

“…Annual minima and maxima were extracted by looking at the windows spanning from May to April, and from January to December, respectively, in order to ensure an appropriate extreme detection. The resulting annual minima and maxima series were then fitted to the Generalized Extreme Value (GEV) distribution (Coles 2001). From the fitted GEV distribution, the probability of exceedance (p) of a given NBS extreme quantile (z p ) can be estimated (often called the return value or return level).…”

“…For example, the 100-year return level, or 0.99 quantile of the probability distribution, has a 1 % chance of being exceeded in a given year. Note that GEV parameters are estimated using the Maximum Likelihood estimation (Coles 2001). We assume that the NBS time series over the present and future (2041-2070) time windows is stationary.…”

“…Therefore, the GEV parameters, and hence the probability of extreme events, are treated as a constant over each time-window. Results of the analysis are summarized in the so-called return level curves (return levels versus return periods), which are associated with 95 % confidence intervals (Coles 2001). Figure 5 shows the return level curves and associated confidence intervals of the present and future climates (green and red lines, respectively) for the Lake Michigan-Huron NBS minima (Fig.…”

Assessment of impact of climate change on water resources: a long term analysis of the Great Lakes of North America

“…Specifically, in the Great Lakes Basin, both empirical and aerodynamic techniques have been used to estimate evaporation, and studies conducted by Cohen (1986Cohen ( , 1990, Sanderson (1987), and Croley (1990Croley ( , 2004 have found that evaporation would be significantly increased under climate change scenarios. Sanderson andSmith (1990, 1993) used the Thornthwaite model and Smith and McBean (1993) used the HELP model and predicted twenty to thirty percent increases in potential evaporation and approximately a 15% increase in actual evaporation to occur.…”

“…However, the Great Lakes basin represents a drainage area of 770 000 km 2 in the United States and Canada (Croley, 1990). Since the water surface area is 244 000 km 2 (US EPA, 2005); it follows that the Great Lakes drain land areas only twice that of their surface area.…”