CLIMATIC SENSITIVITY OF UPLAND ICE FIELDS DURING THE LAST GLACIAL MAXIMUM IN THE TAYLOR RIVER VALLEY, SOUTHERN SAWATCH RANGE, COLORADO

The Taylor River Glacier Complex (TRGC) consisted of multiple outlet lobes, supported wholly or in part by accumulation areas in cirque basins, small ice domes, and upland ice fields. During the local last glacial maximum (LLGM, ~22,500 ¹⁰Be yr B.P.) ice fields comprised a small fraction (not more than 20%) of the TRGC’s total accumulation area. However ice fields were the sole source of nourishment for several of the smaller outlet lobes, and therefore played an important role in the overall development of the TRGC. Given their lack of topographic protection, the ice fields would have been particularly susceptible to both incoming solar radiation and wind deflation of snow. Thus their relative contribution of ice to the TRGC varied significantly through time, increasing in magnitude just prior to, and then peaking during the LLGM. Ice field contribution diminished after LLGM as evidence by the fact that upland surfaces were ice free by ~15,600 (uncorrected) ¹⁴C yr B.P. while ice in the Taylor valley remained at its maximum extent until ~ 16,500 ¹⁰Be yr B.P.

A time-dependent “flow-band” model was used to test the sensitivity of the ice field components of the TRGC. Climatic forcing in the model used degree-day simulations of glacier mass balance. Modeling results support the idea that ice fields were rather transient features of the TRGC, developing late during glaciation and disappearing early during deglaciation. Results furthermore suggest that changes in temperature as little as 1 °C were sufficient to deglaciate upland surfaces.