The Little Ice Age

17 11 2012

The Little Ice Age was the time period to follow the midevil warming period of the start of the last millennium. There was a significant cooling of the climate that caused this Little Ice Age where glaciers in the northwestern Canadian Rockies extended in the proglacial environment from approximately 1400-1600 A.D.

Figure 1. The graph above represents a simplistic idea of temperature variance of the Canadian Rockies over the last 1000 years. Note where the Midevil warming period begins and ends as well as the years Where the Little Ice Age begins.

Glaciers reached their maximum extent during the time frame of the Little Ice Age and show this evidence by moraines that are one of the most dominant landforms of the Canadian Rockies.  Dating these moraines has proven to be extremely difficult as the only way to date the fabric above tree line is through lichenonometry which is the study of lichens and lithobionts that grow on the surface of rocks within the moraines.  However, many of the glacier moraines are below tree line which allows scientists to study the dendrochronolgy of the moraines, or in layman’s terms the study of trees that are growing in post-glacial fields. Using this dating method the oldest tree along the edge of the glacial path is studied to determine how long it was before the retreat, also dead material that has been preserved in the glaciers is often carbon dated to show the age of morainal material. Many of the glaciers in the region can be studied over the last 100 years or so through aerial and ground photography. There are some errors within both dating methods of morainal material that have been accounted for approximately ±5 years.

Figure 2. The image above shows the Athabasica Glacier in the summer of 1917 and September of 1986. There is approximately a 1.5km retreat over the 70 year period, as well as a proglacial lake that was formed in the glacier valley due to the runoff of melt water from the glacier.

Many of the glacier forefields contain moraines that fall between the maximum extent of the Little Ice Age and the current glacier fronts. These moraines are mostly from the time frame between the late 1800’s and early 1900’s. The glacier fronts in the early 1900’s are very close to the moraines that represent the Little Ice Age maximum extent. The highest recessional rates were recorded in the early decades of the 1900’s with a slow downturn as some glaciers advanced slightly between 1950 and 1970. Over the last few decades we have seen another peak in recession of these glaciers, most likely due to climate change.

References

Images and Information

Luckman, Brian H. “The Little Ice Age in the Canadian Rockies.” Geomorphology 32.3-4 (2000): 357-84. Science Direct. Web. 15 Nov. 2012. <http://0-www.sciencedirect.com.skyline.ucdenver.edu/science/article/pii/S0169555X9900104X#&gt;.

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