El Niño, ice cover, and Great Lakes phosphorus: Implications for climate warming

Abstract

Phosphorus concentrations in a 19‐year record of the Lake Huron outflow (Laurentian Great Lakes of North America) were negatively correlated with the extent of Great Lakes winter ice cover. The highest phosphorus concentrations (2–3 times higher than normal) occured during 1983,1987, and 1992 in response to strong El Niño‐related moderation of winter air temperatures. The 1983 winter air temperature anomaly of +2.5°C (the mildest winter in the record) is well within the output of predicted temperature increaces by general circulation models for the Great Lakes basin under a 2× CO2 climate warming scenario. Lake data from strong El Niño years, when contrasted with other years having near‐normal winter temperatures and ice cover, can thus serve to identify some previously unanticipated impacts of global warming on lake water quality. I suggest that global warming may have important implications for eutrophication control in the Great Lakes.