its not. This has NOTHING to do with global warming two issues are at work here. Rebounding land from the last ice age and improved dredging of the sea channels. With improved dredging of the sea channels water is flowing out of the lakes faster. The rate of flow out of the lakes has exceeded the replenishment rate from rainfall.
EDIT: For those who did not know or do not beleive the part about the channels, the US Army Corpse of Engineers performed an in depth survey and found that this is the case. If you search and find thier report you will pre and post flow rates etc. Basically, they messed up. Now they are working on plans to limit the dredging but still support commerce.
Glacial Isostatic Adjustment is the main reason why the lakes water levels are lowering not global warming. It is well documented that most northern hemisphere post glacial locations still experience a 1 mm uplift per year. However, the land is raising and lowering every year on every spot of the globe depending on a meriad of variables such as land movement, horizontal crustal motion, changes in global sea levels, the Earth's gravity field, induced earthquakes and changes in the rotational motion. Changes in sea level are one of the factors that influence the depth of lakes, so that would be the only way that global warming could have an effect. Most areas saw rises of almost 4 inches per year for the first 1500 years after the glaciers melted.
Various things from the needs of the Port of Montreal to winds that push water up or down river control the water level in the St. Lawrence. The port needs enough water to operate properly, so when levels get low, like the recent years, water is held back by dams to build up the Lake Ontario water levels. This will leave my brother's boat in Alexandria Bay NY in mud sometimes, for example. I kayak there a few times a year, and you can see how much lower the river is recently from the water marks on the shorelines, rocks and boathouses. But you can learn a little about it at my first reference, and get a little "local color" with my second, because there are water wars going on.
Just a little background information - the Great Lakes are slowly pouring southward as the Canadian Shield rebounds from the weight of the ice in the last ice age. As the land rebounds, the northern edges of the lakes are lifted faster and higher than the southern, causing the lakes to spill south. As a kid, my family vacationed on Lake Ontario near Henderson Harbor in the late 50's, early 60's, and we stayed in the same place, an actual "little red schoolhouse that had been purchased and moved to the shore for summer rentals. We would go out the back door onto a tiny wooden porch, walk about 10-20 feet on level sand , then the sand sloped down a few feet in a little hill to the lakeshore. A brother went by there while working in the area a couple years ago, and the water is lapping at the bottom of that little wooden porch now. Needless to say, the Port of Montreal is north of the lake, so the water is literally pouring away from the port. It's easier to dam the lake than keep moving the port facilities every decade or so.
************EDIT:
Notice nothing in my answer has anything to do with global warming.
http://www.ijc.org/loslr/en/background/
http://www.northcountrypublicradio.org/n...
First, the Great Lakes are inland lakes and although there maybe could be rising eventually with ocean water making it's way through the St Lawrence, that is a long way off.
The great Lakes are replenished by rain fall and snow melt. Regardless of the lakes level this only accounts for @ 1% of their volume. Increases in temp produces more evaporation, which wont always come back to the lake. In addition, much of the nation has had serious heat waves and drought has been increasing in the Great Lakes states
If Antarcticice studied for years, he might understand half of what I know about a geology but that is doubtful because he has demonstrated a lack of ability to learn. No brag just fact.
I took your question as a good question. Why shouldn't glacier melting increase the water levels in the Great Lakes? They were formed by glaciers after all and if glaciers are all melting, why not?
I thought Joe gave a good answer as well as others.
It certainly has nothing to do with human emissions of CO2 but it does have to do with warming. Global warming is meaningless gibberish that isn't defined. We warmed in our current interglacial which caused the continental glaciers to recede back north. Now we have the isostatic rebound with the land slowly moving upwards to compensate for the lost weight. It is certainly rebounding in the lake as well not just the surrounding land. The lakes were dug out by glaciers.
Humans are using a lot of that water as well but I don't know what effect that has.
Honestly, I don't know the answer to your question with any certainty. I do know the land near the Great Lakes is rebounding upwards but I suspect there are many things at play.
With the lack of understanding this question seems to propose, all I can say is, is that you Jim
The Great Lakes are, well Lakes and the St. Lawrence Seaway is the canal system that connects them to the sea, again sea level is not really at play. Lake Ontario feeds into the seaway but the lake is 74m above sea level.
Lake water levels are not affected by sea level rise, they depend on rain and snow melt in the local area, if the lakes are lower then that suggests less feed in of water, not the point I'm guessing you wanted.
Given that would suggest lower snowfall, which deniers keep trying to, well, deny !
I don't really understand this childish obsession deniers have with trying to claim sea level is not rising, when there is solid evidence that it is.
http://climate.nasa.gov/key_indicators#s...
In fact more than a decade ago scientists suggested one of the outcomes of AGW could be a lowering of the great lakes Lake Ontario which feeds the St. Lawrence River and in turn the Seaway.
http://www.ec.gc.ca/stl/default.asp?lang...
(the above dates back to ~2000)
When Jeff M gets back from searching for the missing heat, get him to go out and find the missing water.
Hm, has anyone thought that Nestle's bottling plant might be taking more water than is being replenished in the area?
they are lowering, since in North America, the groundwater levels have dropped, causing less sea level rise. this was identified by a canadian scientist Richard Peltier
Shouldn't the water levels be getting higher with all the ice melting? Help!
