Hydrothermal structure of a polythermal glacier in Spitsbergen by measurements and numerical modeling

Abstract

Thickness of the upper cold ice layer in the ablation area of the polythermal glacier Grønfjordbreen (Spitsbergen) was estimated by means of numerical modeling. The results were compared with data of radio-echo sounding of the same glacier obtained in 1979 and 2012. Numerical experiments with changing water content in the lower layer of temperate ice and surface snow cover thickness made possible to compare calculated and modeled cold ice thicknesses and to estimate their changes for 33‑year period caused by regional climate change. According to data of radio-echo sounding, thickness of the cold ice layer decreased, on average, by 34 m. Numerical modeling shown similar results: the cold ice layer became thinner by 31 m and 39 m at altitudes 100–300 a.s.l. under the snow cover thickness of 1 m and 2 m. We explain this by rising of annual mean air temperature by 0,6 °С as compared to data of the nearest meteorological station Barentsburg in the same period. We believe that changes in cold ice layer thickness in polythermal glaciers can be used for estimation of changes in such regional climatic parameter as mean air temperature at different altitudes of the glacier surface in the ablation area.

Distribution of cold and temperate ice and water in glaciers at Nordenskiöld Land, Svalbard, according to data on ground-based radio-echo sounding

“…RES data obtained on depth of CTS and thickness of cold ice layer can be used as boundary conditions for numerical modelling and estimation of regional climate changes. This approach was applied for Grønfjordbreen, using the data on CTS depth change for a 33-year period , when the average thickness of the cold ice layer decreased by 34 m. Comparison of calculated and modelled cold ice thicknesses have shown (Sosnovsky et al 2016) that such a change could have occurred in the ablation area of the glacier due to regional climate warming by 0.6°С and this estimate is close to the measured increase in annual mean air temperature at nearest weather station.…”

Snow Thickness on Austre Grønfjordbreen, Svalbard, From Radar Measurements and Standard Snow Surveys

“…По данным радиолокационных измерений в режиме common offset, средняя скорость рас пространения радиоволн в снежном покрове V ср определялась по формуле (2) . Для её вычисления использованы данные измерений общей толщи ны Н В снежного покрова и времени запаздыва ния τ B отражений от подошвы снежного покрова в точках снегомерной съёмки и вблизи шурфов (см .…”

“…Снежный покров существенно влияет на локальный и региональный климат, термиче ский режим подстилающих пород [1][2][3], баланс массы ледников, а также ледниковый и речной сток [4,5] . Основные его параметры -толщи на, структура и плотность -определяют снего запасы и теплоизолирующие свойства снежного покрова .…”