This is an interesting chart that shows levels back to 1870. It indicates to me that over that 136 years the highs have not been as high and the lows have been lower. The trend if there is one would show a general drop of about 3ft over that period of 136 years. If that trend were projected back to 1639 or 367 yrs that would mean a total sustained drop of over 8ft since that time.Hunter and Kidd appear to have been measuring at low ebbs on the cycle and hence there estimates of 10-12ft may seem extreme to some.
3 comments:
While reading a 1995 publication of the Friends of Ste Marie titled Before and Beyond Ste Marie it came upon a statement re water levels based on a 1990 study by Roger Chittenden that show that the water levels were some 3 meters higher than the are today.
FYI - http://www.citizenscientist.ca/ClimateChangeCD/sec4/422c.htm
Did anyone take into consideration "Postglacial Rebound"? If we use Argus, D. F.; Peltier, W. (2008) research - http://adsabs.harvard.edu/abs/2008AGUFM.G31A0646A as a given. We can use Agonquin Park rebound as a reference point. If the rebound for the area is the same as the park's (2.5mm/year) we can calculate the landform being almost a meter lower (.985m) in 1615 than it is today. (2009 - 1615)= 394 years * 2.5mm. So, with the land meter lower we would have a slight variation in shoreline and water intrusion into estuaries and rivers which may help in pinpointing locations of communities.
Thank you for the comment re post glacial rebound and its impact on water levels.
Some discussion on this has taken place and there is little doubt that this rebound effect has altered the shorelines of this region and must be kept in mind when one is trying to determine the cause of the apparent change in water levels that has taken effect over the past four centuries.
Whether the land has risen or the water dropped the result is the same - what the shoreline was in the 1600s is different than it is now and the water level is lower.
The question becomes now - by how much and the answer seem to be by about 3 metres. This result should influence where we look for shoreline sites and the landing places of the 1600s on Southern Georgian Bay. There is no doubt in my mind that the contour of Huronia was different than what we see today - in some areas, substantially.
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