Characterizing the environmental and geochemical landscape of rock glacier outflows in the Intermountain West, USA

Abstract

Listen

Translate article

The global cryosphere is rapidly changing in response to climate warming.  Rock glaciers may be more resilient to climate change than their surface ice and snow counterparts.  However, unlike surface ice features, rock glaciers are comprised of complex mixtures of ice and locally sourced rock, which may be tightly connected to local hydrologic conditions.  This close hydrogeologic connection appears to underlie substantial variability in the environmental conditions of streams associated with rock glaciers, even within the same geographic region.  Here, we analyze 13 years of field data (2011-2023) from 10 rock glaciers and 13 related ice features from four mountain ranges in Wyoming and Utah, USA, to characterize the environmental and geochemical landscape of their outflows.  Specifically, we compare water temperature, geochemistry, conductivity, and isotopic signatures (δ18O and δD) across mountain ranges and ice features.  We find an average surface water temperature of 0.97 ± 1.1 °C across all 10 rock glacier sites from all 13 years; -0.80 ± 0.82 °C at five glacier fed sites, and 1.21 ± 1.88 °C at six snowmelt fed sites.  Preliminary data from two summers of observations also reveal a consistent positive trend in specific conductivity of two rock glacier-fed streams, typical of water transitioning from snowmelt-dominated to ice-melt dominated sources.  Our results highlight the considerable variability in these ecosystems, even within mountain ranges, and underscore the need for wider sampling to better contextualize and monitor them in the future.  This context is critical when considering whether rock glaciers will promote resiliency of coldwater habitat under climate change, and the degree to which their contribution to alpine hydrologic systems may affect biodiversity and drinking water quality as contributions from snow and glacier ice decrease.