The former procedure would generally underestimate this longer term change. 

 (Author) . 



135 HANDS, E. B. 1984. "The Great Lakes as a Test Model for Profile 

 Response to Sea-Level Changes," US Army Corps of Engineers, CERC (Coastal 

 Engineering Research Center), Miscellaneous Report, CERC-84-14, pp 26. 



The average annual water level on Lake Michigan rose 0.8 m between 1967 

 and 1973 causing adjustments in nearshore processes and topography. Assuming 

 2 mm/year as a typical rate for sea- level rise, it would take 400 years to ob- 

 serve similar adjustments on an ocean beach. The rapid rise in average water 

 level is one of several features that makes the Great Lakes useful for testing 

 concepts of shore response to sea- level changes. 



The key assumption in the Bruun concept of response to sea- level rise is 

 that the same average beach profile is reestablished relative to the higher 

 water elevation. This assumption was confirmed by detailed measurements over 

 a 9-year period of 25 beach and offshore profile transects along 50 km of Lake 

 Michigan shoreline. Complete profile adjustment lagged 3 years behind the 

 water level change. 



A simple equation was developed expanding Bruun' s concept to account for 

 (a) gains and losses of sediment from causes other than the water level varia- 

 tion, (b) erosion of different size sediments in the receding shoreface, not 

 all of which would be stable in the shore zone, and (c) accretion of beach 

 material during falling water levels. 



The expanded Bruun sediment balance approach reduces the problem of 

 estimating long-term shore response to sea-level rise to the simpler problem 

 of determining an appropriate closure depth for the responding profile. In 

 the Great Lakes, this closure depth can be estimated as about twice the 5 -year 

 return-period wave height for the site under consideration. Use of a closure 

 estimate based on a Froude Number, similar to Hallermeier ' s offshore limit, 

 may improve transfer of the expanded Bruun approach to those areas of the 

 ocean shore exposed to longer period storm waves. (Author). 



136 HANSEN, J., JOHNSON, D., LACIS , A., LEBEDEFF, S., LEE, P., RIND, D., 

 RUSSELL, G. 1981. "Climate Impact of Increasing Atmospheric Carbon Dioxide,' 

 Science . Vol 213, No. 4511, pp 957-966. 



The global temperature rose by . 2° C between the middle 1960 's and 

 1980, yielding a warning of 0.4" C in the past century. This temperature 

 increase is consistent with the calculated greenhouse effect due to measured 

 increases of atmospheric carbon dioxide. Variations of volcanic aerosols and 

 possibly soar luminosity appear to be primary causes of observed fluctuations 

 about the mean trend of increasing temperature. It is shown that the 

 anthropogenic carbon dioxide warming should emerge from the noise level of 

 natural climate variability by the end of the century, and there is a high 

 probability of warming in the 1980's. Potential effects on climate in the 

 21st century include the creation of drought-prone regions in North America 

 and central Asia as part of a shifting of climatic zones, erosion of the West 



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