Mass balance, runoff and surges of Bering Glacier, Alaska

Abstract

Abstract. The historical net, ablation and accumulation daily balances, as well as runoff of Bering Glacier, Alaska are determined for the 1951-2011 period with the PTAA (precipitation-temperature-area-altitude) model, using daily precipitation and temperature observations collected at the Cordova and Yakutat weather stations, together with the areaaltitude distribution of the glacier. The model mean annual balance for this 61 yr period is −0.6 m w.e., the accumulation balance is +1.4 and the ablation balance is −2.0 m w.e. Average annual runoff is 2.5 m w.e. Periodic surges of this glacier transport large volumes of ice to lower elevations where the ablation rate is higher, producing more negative balances and increasing runoff. Runoff from Bering Glacier (derived from simulated ablation and precipitation as rain) is highly correlated with four of the glacier surges that have occurred since 1951. Ice volume loss for the 1972-2003 period measured with the PTAA model is 2.7 km 3 w.e. a −1 and closely agrees with losses for the same period measured with the geodetic method. It is proposed that the timing and magnitude of daily snow accumulation and runoff, both of which are controlled by the glacier's area-altitude distribution and are calculated with the PTAA model, can be used to determine the probability that a glacier will surge.

Brief Communication: On the magnitude and frequency of Khurdopin glacier surge events

“…Surging glaciers cyclically store ice mass at elevation during periods of quiescence and discharge it down-glacier during periods of activity, making it difficult to differentiate between the influences of external climatic forcing and internal ice dynamics on individual glacier behaviour. Variations in the distribution of ice volume with elevation may also impact on short-term glacier mass balance (Tangborn, 2013), although recent work in the Pamir and Karakoram found no significant difference between the mass balances of surge-type and non-surge-type glaciers over a 10-year period (Gardelle et al, 2013).…”

What glaciers are telling us about Earth's changing climate

“…Linear regressions of model vs. measured annual balances yields R 2 values of 0.20 to 0.70 (Table 1). Application of the model to Bering Glacier in Alaska demonstrated a close agreement with ice volume loss for the 1972-2003 period measured with the geodetic method (Tangborn, 2013). The first application of the model was for the rapidly retreating Columbia Glacier in Alaska (Tangborn, 1997).…”

“…The PTAA model (Precipitation-Temperature-Area-Altitude) is dependent on the cli-mate history that is embedded in the glacier's surface configuration (its area-altitude distribution) and relies on the internal consistency of mass balance variables, for ex-ample the relationship between snowline elevation and glacier balance. Detailed ex-planations of the model and how it functions are provided in Tangborn (1997Tangborn ( , 1999Tangborn ( , 2013, and Tangborn and Rana, (2000). In the PTAA model, snow and ice ablation is calculated at each elevation interval from the observed daily mean temperature and the diurnal temperature range, based on the temperature lapse rate that is also calculated from temperature observations.…”

A new sub-grid surface mass balance and flux model for continental-scale ice sheet modelling: testing and last glacial cycle

“…We use the positive degree day method described in Tarasov and Peltier (1999) to compute accumulation and ablation from monthly mean temperature and precipitation. A constant environmental lapse rate adjusts the temperature to the ice surface elevation.…”