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Southern Alaska, USA
Reference
Wiles, G.C., Barclay, D.J., Calkin, P.E. and Lowell, T.V. 2008. Century to millennial-scale temperature variations for the last two thousand years indicated from glacial geologic records of Southern Alaska. Global and Planetary Change 60: 115-125.

Description
Wiles et al. used temperature-sensitive climate proxy records with tree-ring, lichen and radiocarbon dated histories from five land-terminating non-surging glaciers located just above the Gulf of Alaska (about 60N between 140 and 150W) for the last two millennia to "identify summer temperature as a primary driver of glacial expansions." This work provided evidence for the Medieval Warm Period that consisted of "soil formation and forest growth on many forefields in areas that today are only just emerging from beneath retreating termini," which suggests that the Medieval Warm Period was likely both warmer and longer-lived than what we have so far experienced during the Current Warm Period. They also report that "tree-ring chronologies show that forest growth on these forefields was continuous between the 900s and 1200s" at the Sheridan, Tebenkof and Princeton glaciers.