Weather Whys, February 10, 2013

More temperature see-saw in February; Lake Superior and the Upper Great Lakes
Lake levels decline over the winter season. There is usually reduced precipitation directly in the Lake, considerable evaporation and reduced runoff from the surrounding basin. Lake Superior, as a result of spring runoff and rainfall during the spring and summer seasons typically recovers about 30 cm (one foot) by late summer. The Lake is presently about 30 cm (one foot) below its February average. The Greatest Lake is currently 60 cm (two feet) below its long term average.

All the Great Lakes are below their long term average, although the super winter storm during the last couple of days will help water levels in Lake Ontario and Erie. There are obvious direct implications of unusually low water levels. These include reduced fish spawning, reduced loads on ships, reduced wetlands and, not to overuse the negative word “reduced” – increased beaches and increased potential for problems with drinking water supply.

Lake Superior has been lower than its long term average since 1998. Some people talk of a cycle which will rescue the situation. The history of Superior (from 1860) suggests – don’t hold your breath.

Lake Superior was at or near record low levels during 1924 to 1926. This was followed by a recovery over three years. Higher than average levels occurred from the late 1930s to the mid-1950s several times. These peak levels were related to the Long Lac and Ogoki diversions and a number of high precipitation years. There is little variation from the mid-1950s to the later 1990s. Minor and brief peaks take place once per decade in the second half of the 20th Century.

In other words, nothing comparable in duration plus a recovery occurs in past records.

Record low water levels in Lakes Michigan and Huron are in the news these days. The historical highs and lows in Lake Superior and Michigan/Huron are not identical but the 15-year period of low water is shared by all the upper Great Lakes.

The city of Chicago is especially vulnerable to the record low level of Lake Michigan. The problems include threats to drinking water and the likelihood that water flow will reverse direction in a river and canal system if Lake Michigan levels decline any more.

The upper Great Lakes are critically low. There is some policy discussion in the US but little in Canada. Oddly enough, some of the discussion south of the border uses a recent study conducted in Canada. This study notes that if all Great Lakes “cargo were moved to trucks, it would spur a 533 per cent increase in greenhouse gases [and increase] particulate emissions by 85 percent”.


This discussion vacuum in Canada is suspicious.