By Meredith Rodriguez
Most years, the Coast Guard's vessels start spending their nights in Calumet Harbor around the end of February. This year, they remained in heated garages until recent weeks, safely away from the shrinking but still formidable ice cover on Lake Michigan that has been moving with the wind in and out of Chicago's harbors.
"Yesterday it looked clear," Mark Stevens, commanding officer at the Coast Guard's Calumet Harbor, said recently. "Then this morning, when I got to the office, there was all this ice blown back."
Farther out on the Great Lakes, while the Soo Locks that connect Lake Superior to the lower Great Lakes opened on schedule last week to make way for commercial ships coming out of their winter hibernation, ice breaking that started earlier than ever this season on Dec. 6 is also expected to extend well into May, according to Glen Nekvasil, president of the Lake Carriers' Association.
"With the ice being as thick as it is, we're going to need more than a couple of sunny days to loosen it up," Nekvasil said. "If this is like 1994, the Coast Guard would be breaking ice in St. Mary's River until May 18, and this looks to be every bit as bad as '93-'94."
The Great Lakes community can take the unrelenting inconveniences of this brutal winter in stride, however, as it looks forward to the much-needed benefit it is expected to bring to lake levels this spring.
"We'll see the effect of this harsh, snowy winter play out over the next several months," said Keith Kompoltowicz, chief of watershed hydrology at the Army Corps of Engineers Detroit District. As the record-breaking 93.29 percent ice cover that peaked on Lake Michigan in March breaks, and as the snowpack around the Michigan Basin that was 30 percent higher this year than any time in the past decade melts, water levels will undergo a stronger-than-usual seasonal rise, according to Kompoltowicz.
The lake is expected to rise 14 inches by August, according to predictions for the next six months by the Corps of Engineers, announced last month.
The rise comes after water levels on the Great Lakes _ and particularly the unified Lake Michigan-Huron system _ have languished below their long-term average for 14 years. Water levels have always fluctuated, but they have never in their 95-year recorded history remained below average for so long.
Lake Michigan reached a record low in January 2013, 2.78 feet below the lake's long-term average.
"It was certainly an extreme situation," Kompoltowicz said of last year. "Any time you set a record low, it certainly garnered a lot of attention."
Unlike previous lows that could largely be attributed to varying rainfall, this recent low has largely been attributed to increased evaporation due to climate change, according to Andrew Gronewold, a hydrologist with the National Oceanic and Atmospheric Administration's Great Lakes Environmental Research Laboratory.
This year's ice cover decreased that evaporation by acting as a shield between water and air, but more importantly and often overlooked, it is now acting as an ice cube as it melts, keeping water temperatures low and contributing to lower evaporation into fall, according to John Lenters, an environmental scientist who published a paper on evaporation on the Great Lakes earlier this year.
"The effect of a (ice) cap is less important than the delaying of next year's evaporation season," Lenters said.
Evaporation happens when cool air meets warm water, Lenters said. While the high evaporation season would usually arrive in July or August, this year it might be as late as September, a delay that could make as much as a 10-inch difference, he said.
In addition to runoff and evaporation, precipitation creates the greatest impact on lake levels, and that is the least predictable element.
"The big wild card is what rainfall will do," Lenters said. "It's hard to forecast that very far out in advance because it's highly dependent on weather systems coming in from outside the weather basin."
While drought contributed to the record-low water levels in January 2013, Lenters said, rain was plentiful last spring when the lake rose 20 inches, instead of the average 12 inches. If rainfall is as heavy as last year, Kompoltowicz said, Lake Michigan could rise as much as 20 to 22 inches in the coming months.
Higher levels will improve the health of wetlands and wildlife around the lakes, scientists say. When water levels are as low as they were, fish species that run up rivers and creeks to spawn can't, according to Edward Rutherford, research fishery biologist at NOAA's Great Lakes Environmental Research Laboratory. Higher water levels likewise expand the habitat for fish eggs along the coast, he added.
When low water levels keep wetlands dry over a long period of time, invasive plant species begin to take over, according to Kurt Kowalski, a wetland ecologist with the USGS Great Lakes Science Center.
"They might start creeping down the slope," Kowalski said, "until water levels come back up and flood them out."
Variation in water levels that the lake will experience this year is ideal for wetlands, Kowalski said. When dry areas flood out, the new plant life that formed above water creates welcome protection for fish from predators.
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