A Methodology to Estimate Year-Round Effects of Climate Change on Water Temperature, Ice and Dissolved Oxygen Characteristics of Temperate Zone Lakes with Application to Minnesota

Abstract

A deterministic, one-dimensional model has been developed and applied which simulates daily water temperature and dissolved oxygen (D.O.) profiles and associated ice covers and snow covers for dimictic and polymictic lakes of the temperate zone. The only lake parameters required as model input are surface area (As), maximum depth (HMAX), and Secchi depth is used as a meaSure of light attenuation and trophic state. All other lake characteristics required by the model are related to these three parameters. The relationships used were derived from Minnesota lake data, and hence the model is considered to be a regional model. The model is driven by daily weather data and operates year-round over multiple years (with initial water temperature and D.O. profiles specified on April 16 of the first year). Because of this specific feature, the model can be used to simulate the effect of different climate scenarios on lake water quality characteristics, i.e. water temperatures, D.O. concentrations, stratification, and ice cover characteristics. The model has been validated with extensive data from lakes in Minnesota and one Wisconsin lake. Standard errors between simulations and prediction of over 5,000 temperature/D.O. data pairs are I ADe for water temperature and 1.9 mg/I for D.O. In this report simulated lake characteristics are reported for past weather conditions, which were recorded at two stations in Minnesota from 1961 to 1979, and for climate conditions which are projected to exist if the atmospheric CO2 doubles. The projected changes in climate conditions were obtained from the output of the Canadian Climate Center Global Circulation Model (CCC GCvl) and the Goddard Institute of Space Studies at Columbia University (G1SS) GCM. The projected relative changes in climate parameters due to a doubling of atmospheric CO2 were applied to the past (1961-1979) weather record, and the resulting modified weather data time series were used as input to the lake simulations in order to project lake temperature and D.O. if the atmospheric CO2 doubles.