SIMULATED CLIMATE-CHANGE EFFECTS ON DISSOLVED-OXYGEN CHARACTERISTICS IN ICE-COVERED LAKES

A deterministic, one-dimensional model is presented which simulates da ily dissolved oxygen (DO) profiles and associated water temperatures, ice covers and snow covers for dimictic and polymictic lakes of the te mperate zone. The lake parameters required as model input are surface area (A(S)), maximum depth (H-MAX), and Secchi depth as a measure of l ight attenuation and trophic state. The model is driven by daily weath er data and operates year-round over multiple years. The model has bee n validated with extensive data (5976 points). Standard error between simulated and measured dissolved oxygen is 1.9 mg/l. The model is appl ied to simulate effects of climate change on dissolved oxygen characte ristics of 27 lake classes in Minnesota. The projected climate changes due to a doubling of atmospheric CO2 are obtained from the output of the Canadian Climate Center Global Circulation Model (CCC GCM). Climat e change delays the ice formation and shortens the ice cover period. W inter anoxia, even in shallow lakes, therefore disappears under a proj ected 2 x CO2 climate condition. This eliminates winterkill in these l akes. Herein, the simulated DO characteristics have been plotted and i nterpolated graphically in a coordinate system with a lake geometry ra tio (A(S)(0.25)/H-MAX) On one axis and Secchi depth on the other. The lake geometry ratio expresses a lake's susceptibility to stratificatio n. To illustrate the effect of projected climate change on DO characte ristics, separate graphs are presented for values simulated with input s of past climate conditions (1961-79) and with a projected 2 x CO2 cl imate scenario. (C) 1997 Elsevier Science B.V.