Glacial equilibrium line–based relationship for paleoclimate reconstructions (Sierra Nevada, USA)

Abstract

AbstractWe use PRISM climatic data (1981–2010) and Landsat images (2012–2013) to establish an empirical relationship linking annual temperature and precipitation to the equilibrium line altitude (ELA) of glaciers in the Sierra Nevada (36–41°N, California, USA). For this, we determined the present-day ELAs of 57 glaciers and the local 0°C isotherms elevation Iso0, averaged over the 1981–2010 period. The difference, for each glacier, is Y, the normalized snowline altitude (Y = ELA – Iso0). We then empirically calibrated a logarithmic relationship between this normalized snowline altitude and mean annual precipitation using data from partially covered glaciers. Our calibration is statistically distinct from that previously established for the tropical and midlatitude Andes (Fox and Bloom [1994], Journal of Geography (Chigaku Zasshi), 103, 867–885; Condom et al. [2007], Global and Planetary Change, 59, 189–202). This new relationship for North America is an easy-to-use tool to permit paleoclimatic reconstructions from paleo-ELAs. For a specific paleoglacial site, paleotemperature can be computed knowing the paleoprecipitation range, and vice versa. We also performed a test showing that, if precipitation is well known, the uncertainty associated with paleotemperature is about 1°C (1σ).