Per the images above, on February 13th, 2014, Great Lakes Ice Coverage was 88.4%. On February 14th, Ice Coverage dropped to 80.2 %, and has expanded only slightly to 81.4% in the two days since. The reason for this drop in Ice Coverage does not appear to be related to temperature, as it has remained below freezing over the Great Lakes during the period in question:
The most likely cause of the decrease in Great Lakes Ice Coverage is wind, which compacted the Lake Ice, thus decreasing coverage. However, anthropogenic influences may also have played a role. Let us take a look.
“Sections of the lakes, which hold nearly one-fifth of the freshwater on the world’s surface, harden almost every winter. That freezing keeps the Coast Guard’s fleet of nine icebreakers busy clearing paths for vessels hauling essential cargo such as heating oil, salt and coal. But over the past four decades, the average ice cover has receded 70 percent, scientists say, probably in part because of climate change.”
“For Coast Guard icebreaker teams, it’s all business. They’ve logged four times more hours this season than the average for the same period in recent years, said Kyle Niemi, spokesman for the agency’s Cleveland district headquarters.
The 240-foot-long Mackinaw began its duties Dec. 16 – several weeks earlier than usual – and worked nonstop until Feb. 8, when traffic slowed enough to allow a break.”
“A 35-year Coast Guard veteran who has spent 12 years on the lakes, Davanzo said this winter is the toughest he’s experienced because the ice came so soon and is so thick and widespread, and the weather has been constantly bitter.
The Mackinaw, commissioned in 2006 to replace an older vessel with the same name, is designed specifically for duty on the Great Lakes. It’s propelled by two “Azipod” thrusters that can spin 360 degrees and fire jets of water at adjacent ice, weakening it. Sometimes the crew will drive the ship’s bow onto an ice sheet to crack it with sheer weight. Or they’ll go backward, chopping up ice with the propeller blades.
When the going gets tough, there’s the battering-ram option – hurling the reinforced hull directly against walls of ice that can be several feet thick.”
“The workload typically drops sharply after navigational locks on the St. Marys River, the link between Lakes Superior and Huron, close in mid-January and most large cargo haulers dock for winter. But the ice was so thick this year that a number of freighters were still struggling to complete final deliveries days later. Even now, demand for road salt and heating oil in the Midwest is keeping some icebreakers busy.”
“If the weather stays like this,” he said, “we could be breaking ice all the way to the middle of May.” AOL
If you look at the following image from Feb. 6, 2014 of Lake Huron facing towards Port Huron, Michigan on the right, and Sarnia, Ontario on the left, you’ll note the icebreaker/ship trail on the left side of the image:
It appears that the icebreaker/ship may have created a weakened portion of the ice, which may be more susceptible to breakage and movement due to winds. Additionally, in the background of the image you can see steam rising from industrial production and you can see that lake ice hasn’t formed in the inlet and areas along the coast. This leads us to our second potential anthropogenic influence, i.e. waste heat.
“Many large thermoelectric power plants were built on the shores of the Great Lakes because the lakes provide easy access to the large volumes of water require for plant cooling. Thermoelectric power generation is the largest use of water in the Great Lakes basin (72% of all water use in 2005), with the majority used as cooling water.” “Most Great Lakes coastal power plants use once-through cooling technology. Plants withdraw water using large underwater pipes, sometimes located up to 1000 meters offshore, circulate the water through their plants, and then discharge heated water back to the lake.” Great Lakes Mapping
“Our analysis includes 114 coastal power plants located within 2 km of the Great Lakes shoreline on the assumption that these plants draw water directly from the Lakes or from major tributaries just upstream of their confluence with the Lakes.” “”It is evident that apart from heat discharged with combustion gases from a coal-burning plant and any difference in thermal efficiency which affects the amount of heat to be dumped in the cooling system, there is no real difference in the amount of water used for cooling nuclear power plants, relative to coal-fired plants of the same size.” World Nuclear.org
“Cooling to condense the steam and discharge surplus heat.” “If the power plant is next to the sea, a big river, or large inland water body it may be done simply by running a large amount of water through the condensers in a single pass and discharging it back into the sea, lake or river a few degrees warmer and without much loss from the amount withdrawn. That is the simplest method. The water may be salt or fresh. Some small amount of evaporation will occur off site due to the water being a few degrees warmer.” “The amount of water required will be greater than with the recirculating set-up, but the water is withdrawn and returned, not consumed by evaporation. In the UK the water withdrawal requirement for a 1600 MWe nuclear unit is about 90 cubic metres per second (7.8 GL/d).”
“Any nuclear or coal-fired plant that is normally cooled by drawing water from a river or lake will have limits imposed on the temperature of the returned water (typically 30°C) and/or on the temperature differential between inlet and discharge. In hot summer conditions even the inlet water from a river may approach the limit set for discharge, and this will mean that the plant is unable to run at full power. In mid 2010 TVA had to reduce power at its three Browns Ferry units in Alabama to 50% in order to keep river water temperatures below 32°C, at a cost of some $50 million to customers. This was the same week when Rhine and Neckar River temperatures in Baden-Wuerttemberg approached the critical 28°C, and nuclear and coal-fired plants were threatened with closure. In August 2012 one unit of Millstone power station in Connecticut was closed because the seawater in Long Island Sound exceeded 24°C.”
“In France, all but four of EdF’s nuclear power plants (14 reactors) are inland, and require fresh water for cooling. Eleven of the 15 inland plants (32 reactors) have cooling towers, using evaporative cooling, the other four (12 reactors) use simply river or lake water directly. With regulatory constraints on the temperature increase in receiving waters, this means that in very hot summers generation output may be limited.*
* For instance at Bugey, the maximum increase in water temperature in summer is 7.5ºC normally, and 5.5ºC in summer, with maximum discharge temperature 30ºC (34ºC in summer) and maximum downstream temperature 24ºC (26ºC allowed for up to 35 summer days). For plants using direct cooling from the sea, the allowed temperature increase offshore is 15ºC.”
“Dredging in the St. Clair River has increased the flow capacity out of Michigan and Huron. There are also three man-made diversions that manipulate the amount of water entering and the leaving the Great Lakes, the most notorious of which is the 113-year-old Chicago canal, which carries the city’s wastewater into the Mississippi.” “But the water lost from the Great Lakes at Chicago is more than compensated for by two Canadian diversions that channel water out of the Hudson Bay watershed and into Lake Superior.” Journal Sentinel Online
In terms of the impact of dams and reservoirs on water temperatures, “the altered chemistry of reservoir water affects the ecology of a diminished river for many kilometers downstream, leading to greater climactic ramifications. When the Krasnoyarskaya Dam (one of the world’s most powerful at 6000 MW) was built on the Yenisei River, its designers predicted that warm water releases from the reservoir would prevent the river from freezing for about 20 kilometers downstream. However, the unfrozen stretch of water extends 200-300 kilometers from the dam, which in the depths of the Siberian winter, causes thick freezing fog to cloud the city of Krasnoyarsk.” Pacific Environment
While there is no definitive evidence, there appears to be circumstantial evidence that there may be anthropogenic influences on Great Lakes Ice Coverage. What do you think, are there anthropogenic influences impacting Lake Ice Coverage? If so, which anthropogenic influences do you think have a significant impact?