The Great Lakes Freighters Carrying Michigan's Economy

Long before a Michigan-built vehicle rolls off a line, the raw material behind it often arrives by water. The Great Lakes shipping season — the months when freighters haul iron ore, limestone, grain, and coal across the inland seas — is one of the least visible and most important gauges of the state's industrial health.

Reading the tonnage

This season's cargo volumes have run strong, particularly for iron ore and stone, the inputs that feed steelmaking and construction. Higher tonnage is a leading indicator: freighters move material weeks or months before it becomes a finished product, so a busy shipping season tends to foreshadow a busy factory season.

"The lakes are a barometer," said port logistics manager Owen Delaronde. "When the boats are full, the plants downstream are about to be busy."

The seasonal squeeze

The fleet's great constraint is winter. Ice closes the locks and narrows the shipping window, forcing shippers to move a year's worth of certain materials in a compressed span. A strong season is good news; a strong season achieved without weather disruptions is better. So far, the water has cooperated — and Michigan's furnaces and job sites are the beneficiaries.