A Mass Balance Model of Lyell and Maclure Glaciers in Yosemite National Park

Abstract:

The Lyell and Maclure glaciers, two historically important glaciers of Yosemite National Park, have been rapidly retreating since the late 1800's. I attempted to quantify the water balance of two basins containing these glaciers. Water inputs were calculated by applying snow pillow data and two precipitation vs. elevation slope models. Water outputs consisted of a simplified evapotranspiration model and stream runoff data. Fifty-six linear combinations of precipitation and evaporation were used to develop water balance models. Most of these models predicted melt rates from the two glaciers outside of empirical observations. However, both the Lyell Glacier Basin and the Lyell Fork of the Tuolumne Basin water balance spreads had notable Kolmogorov-Smirnov test statistics: Lyell Glacier with p = 0.34 for 2013 and p = 0.37 for 2014, and Lyell Fork with p = 0.45 for 2009. The basin containing Lyell Glacier had a water balance spread of between $-1,105\times{10^3}m^3$ and $+58\times{10^3}m^3$ (interquartile range) with a mean of $-564\times{10^3}m^3$ for the 2013 hydrologic year, and between $-1,137\times{10^3}m^3$ and $+21\times{10^3}m^3$ (interquartile range) with a mean of$-583\times{10^3}m^3$ for the 2014 hydrologic year. The Lyell fork of the Tuolumne basin containing both Lyell and Maclure Glaciers had a water balance spread of between$-14,350\times{10^3}m^3$ and $+7,454\times{10^3}m^3$ (interquartile range) with a mean of $-2,426\times{10^3}m^3$ for the 2009 hydrologic year. Variations observed in water balance models for Lyell Glacier in this study are an order of magnitude larger than the expected melt signal, and two orders of magnitude for the Lyell Fork of the Tuolumne water balance models.