Freezing and Frostbite on Mount Everest: New Insights into Wind Chill and Freezing Times at Extreme Altitude

Abstract

Cold injury is an acknowledged risk factor for those who venture into high altitude regions. There is, however, little quantitative information on this risk that can be used to implement mitigation strategies. Here we provide the first characterization of the risk of cold injury near the summit of Mount Everest. This is accomplished through the application of a meteorological dataset that has been demonstrated to characterize conditions in the region as inputs to new parameterizations of wind chill equivalent temperature (WCT) and facial frostbite time (FFT). Throughout the year, the typical WCT near the summit of Everest is always <-30°C, and the typical FFT is always less than 20 min. During the spring climbing season, WCTs of -50°C and FFTs of 5 min are typical; during severe storms, they approach -60°C and 1 min, respectively; values typically found during the winter. Further, we show that the summit barometric pressure is an excellent predictor of summit WCT and FFT. Our results provide the first quantitative characterization of the risk of cold injury on Mount Everest and also allow for the possibility of using barometric pressure, an easily observed parameter, in real time to characterize this risk and to implement mitigation strategies. The results also provide additional confirmation as to the extreme environment experienced by those attempting to summit Mount Everest and other high mountains.

Environmental conditions at the South Col of Mount Everest and their impact on hypoxia and hypothermia experienced by mountaineers

“…During the spring climbing season, WCTs of −50°C and FFTs of 5 min are typical; while during severe storms, they can approach −60°C and 1 min, respectively. During the May 1996 ‘Into Thin Air’ storm, the instantaneous WCT and FFT approached values typically found during the winter months [17]. This work highlighted the crucial role that wind speed played in increasing the hypothermic stress near the summit and also confirmed that the previous estimate was biased low as a result of the assumption as to the magnitude of the wind speed in the region [16].…”

“…In addition, it must be emphasized that these expressions were derived at sea level and there are meteorological and physiological issues with applying them at altitude [16,17]. In particular, the convective heat loss is proportional to the square root of the Reynolds number, which in turn depends on the product of the air density and wind speed [25].…”

“…The measurements at the South Col were made at a height of 3 m (Table 1), and the scaling requires an effective increase of 50% in the wind speed in the expressions for WCT and FFT [23]. These two effects would cancel out to first order [17], and as a result, we have chosen to make no correction to the wind speed. In addition to these meteorological effects, the physiological effects of high altitude including hypoxia and dehydration can exacerbate the hypothermic stress as compared to sea level [2,26].…”

“…The first quantitative estimate of the risk of cold injury at high altitude has only recently been provided [17]. This was accomplished through the use of temperature and wind speed data extracted from global meteorological datasets of the sort that were validated previously with data from the Mount Everest region [15,18].…”

“…This study focused on two parameters: the WCT and the facial frostbite time (FFT), defined as the time it takes for facial flesh to freeze. Throughout the year near the summit of Mount Everest, it was shown that the typical WCTs and FFTs are always less than −30°C and 20 min, respectively [17]. During the spring climbing season, WCTs of −50°C and FFTs of 5 min are typical; while during severe storms, they can approach −60°C and 1 min, respectively.…”