Retreating Glacier In Patagonia Uncovers 400 Year Old Forest

By Paul Homewood

h/t agfosterjr

 

Yesterday we looked at the Exit Glacier in Alaska, where the retreating ice had uncovered remains of a medieval forest. Today we will have a look at the Glaciar Jorge Montt in  Patagonia, where forest remains have also been uncovered, these dated to about 460 years ago.

 

 

Little Ice Age Advance and Retreat of Glaciar Jorge Montt, Chilean Patagonia.

By A Rivera et al.

ABSTRACT

Glaciar Jorge Montt, one of the main tidewater glaciers of the Southern Patagonian Icefield (SPI), has experienced the greatest terminal retreat observed in Patagonia during the past century, with a recession of 19.5 km between 1898 and 2011. This retreat has revealed trees laying subglacially until 2003. These trees were dated using radiocarbon, yielding burial ages between 460 and 250 cal yrs BP. The presence of old growth forest during

those dates indicates that Glaciar Jorge Montt was upvalley of its present position before the commonly recognized Little Ice Age (LIA) period in Patagonia. The post-LIA retreat was most likely triggered by climatically induced changes during the 20th century; however, Glaciar Jorge Montt has responded more dramatically than its neighbours. The retreat of Jorge Montt opened a 19.5 km long fjord since 1898, which reaches depths in excess of 390 m.

http://www.clim-past.net/8/403/2012/cp-8-403-2012.pdf

   

As the photo below makes clear, the tree remains were found right at the edge of where the glacier stood as recently as 2010. For trees to grow in this position, it is likely that the edge of the glacier at the time was a distance uphill of its present position.

It seems also extremely unlikely that these are the only tree remains under the present glacier, and that many more will be revealed as/if the glacier continues to retreat. Lonnie Thompson, for instance, finds that, on the Quelccaya Glacier in Peru, temperatures peaked in the 14thC, two centuries before these trees were growing.

 

One other interesting comment made in the study:-

 

“During the LIA the glacier advanced to most likely stabilize at the 1898 position”

   

As we find elsewhere, glaciers were reaching their maximums just at the time we started studying them.

 

Footnote

There is plenty of evidence throughout South America of a Little Ice Age, preceded by a Medieval Warming Period that may have been warmer than the current period.

For instance, here.