First investigation of perennial ice in Winter Wonderland Cave, Uinta Mountains, Utah, USA

Abstract

Abstract. Winter Wonderland Cave is a solution cave at an elevation of 3140 m above sea level in Carboniferous-age Madison Limestone on the southern slope of the Uinta Mountains (Utah, USA). Temperature data loggers reveal that the mean annual air temperature (MAAT) in the main part of the cave is −0.8 ∘C, whereas the entrance chamber has a MAAT of −2.3 ∘C. In contrast, the MAAT outside the cave entrance was +2.8 ∘C between August 2016 and August 2018. Temperatures in excess of 0 ∘C were not recorded inside the cave during that 2-year interval. About half of the accessible cave, which has a mapped length of 245 m, is floored by perennial ice. Field and laboratory investigations were conducted to determine the age and origin of this ice and its possible paleoclimate significance. Ground-penetrating-radar (GPR) surveys with a 400 MHz antenna reveal that the ice has a maximum thickness of ∼ 3 m. Samples of rodent droppings obtained from an intermediate depth within the ice yielded radiocarbon ages from 40±30 to 285±12 years. These results correspond with median calibrated ages from CE 1560 to 1830, suggesting that at least some of the ice accumulated during the Little Ice Age. Samples collected from a ∼ 2 m high exposure of layered ice were analyzed for stable isotopes and glaciochemistry. Most values of δ18O and δD plot subparallel to the global meteoric waterline with a slope of 7.5 and an intercept of 0.03 ‰. Values from some individual layers depart from the local waterline, suggesting that they formed during closed-system freezing. In general, values of both δ18O and δD are lowest in the deepest ice and highest at the top. This trend is interpreted as a shift in the relative abundance of winter and summer precipitation over time. Calcium has the highest average abundance of cations detectable in the ice (mean of 6050 ppb), followed by Al (2270 ppb), Mg (830 ppb), and K (690 ppb). Most elements are more abundant in the younger ice, possibly reflecting reduced rates of infiltration that prolonged water–rock contact in the epikarst. Abundances of Al and Ni likely reflect eolian dust incorporated in the ice. Liquid water appeared in the cave in August 2018 and August 2019, apparently for the first time in many years. This could be a sign of a recent change in the cave environment.