Lake level fluctuation since 1860 and future predictions.
Image: National Oceanic and Atmospheric Administration (NOAA) Great Lakes Environmental Research Laboratory
LANSING — A changing climate in the Great Lakes region should worry the shipping industry if it leads to lower water levels that reduce how much cargo can be shipped, according to a recent federal report.
The National Climate Assessment released in early May reports that the winter of 2012 — 2013 had the least ice coverage on the Great Lakes since 1963. Lower ice leads to more evaporation and that means water levels decline, said Anne Clites, a physical scientist at the National Oceanic and Atmospheric Administration’s (NOAA) Great Lakes Environmental Research Laboratory.
That’s part of a long-term trend that didn’t hold true this past winter.
This year’s extensive ice cover may make a small impact by reducing evaporation and raising this summer’s water levels. Cooler temperatures reduce evaporation.
But this year is an outlier, Clites said. The long-term trend shows a steady decrease in ice cover and an increase in evaporation.
Most lakes get to their highest levels in July, August or September, said Clites. They start going down in the fall, when most evaporation occurs.
The two factors driving water levels are precipitation and evaporation, said Clites.
If the ice cover continues to decrease, it will leave exposed lake surfaces that provide moisture to fuel rain and snow, said Elizabeth Gibbons, a project manager at the Great Lakes Integrated Science and Assessment Center, a collaboration of theUniversity of Michigan and Michigan State University that examines adaptations to climate change in the region. It is part of a network of NOAA Regional Integrated Sciences and Assessments Centers. Most climate models project that evaporation from the Great Lakes will outpace increases in precipitation, she said.
“With more water leaving the basin than there is returning, the result could be less water remaining in the Great Lakes,” said Gibbons. “Changing evaporation from the lake and land surfaces is still an active area of research, however, understanding the balance of precipitation with evaporation is one of the largest sources of uncertainty to projections of lake levels.”
Clites’ group reports a significant increase in evaporation over the past 13 years that coincides with a decrease in ice coverage.
The consequences could be severe.
The lowering of water levels results in a severe dip of the amount of cargo that can be shipped, said Glen Nekvasil, vice president of the Lake Carriers’ Association.
Draft refers to how deep a ship sits in the water. Depending on the ship size, there can be a loss of 50 to 270 tons of cargo for every inch of draft that is lost, said Nekvasil.
The reduction of shippingcould halt or slow production throughout the region, said Nekvasil. Shipping is the region’s main transportation for raw materials.
Many power plants get their coal via the lakes, he said. Steel mills get their iron ore this way.
Ships are very sensitive to the fluctuation of lake levels, said Gibbons. The typical 1,000 — foot freighter loses about $30,000 of revenue for each inch of lost draft, she said.
“Since freighters typically carry as much as they possibly can and still safely navigate the shallowest sections of their route, even a small decline in long-term lake levels can be costly,” said Gibbons. “Marinas and harbors, particularly those in shallow areas or those that utilize aging infrastructure, may be critically affected and unable to function in low -level years.”
Nekvasil says the solution is dredging out the sediment and mud that is found in these harbors. This past winter was one of the harshest winters in the century. It will result in more water, but dredging is still required, he said.
“To get the system back to the depth that it was supposed to be we would have to remove 18 million cubic yards of sediment,” Nekvasil said.
That’s enough to fill a string of typical 15-yard mulch trucks from Muskegon Mich, to Beijing, China.
On the positive side for shipping, the report says that reduced ice cover extends the shipping season.
But it’s not enough to offset the other problems, Nekvasil says.
Other factors, like maintenance on the ports and ships prevents a long season extension, said Nekvasil. Ships run 24-7 and they must periodically be brought in for maintenance.
Brent Lofgren, another physical scientist at NOAA’s Great Lakes Environmental Research Laboratory, says there is plenty of cause for concern.
“The climate change effects on lake levels is still a matter of considerable uncertainty, but uncertainty is something we should be concerned about because it means the possibility of several different outcomes we might need to anticipate.”