Little ice age history of Tzeetsaytsul Glacier, Tweedsmuir Provincial Park, British Columbia

This paper describes lichenometric and dendroglaciological investigations o f Little Ice Age (LIA) deposits at Tzeetsaytsul Glacier, Tweedsmuir Provinc ial Park, British Columbia. The glacier originates from an icefield on the northeast flank of Tzeetsaytsul Peak and terminates in a moraine-dammed lak e. A stream draining the lake has incised the moraine dam and flows through nested moraines into a second lake. Two end moraines near the lower lake r ecord separate advances, with numerous morainic ridges found between the tw o lakes. A locally calibrated Rhizocarpon geographicum growth curve was con structed and provides relative ages for all the moraines. Absolute dates fr om wood fragments collected from within the morainic debris were determined by matching their annual growth ring patterns to a local Abies lasiocarpa tree-ring chronology. The outermost terminal moraine was deposited by a 17t h century advance that culminated in ca. 1700. Following subsequent recessi on, Tzeetsaytsul Glacier readvanced to build a second terminal moraine by t he mid-1800s. Recession of this glacier occurred within 40 years and by 193 5 the glacier was beginning to cake into the uppermost lake. The research s hows that the most recent LIA advance of Tzeetsaytsul Glacier was not the m ost extensive, and that multiple events characterized the late-LIA. Applica tion of the Rhizocarpon growth curve indicates a previously unreported 17th century advance at other glaciers in the region. These findings serve to r einforce the synchroneity of late-LIA glacier fluctuations within the coast al cordillera of NW North America suggesting that they record regional clim ate forcing.