Speaking about heat flow, ice fusion and temperature alterations

Abstract

Heat flow density measurements are difficult to obtain in Antarctica and Greenland due to climate and ice thickness in those regions. The works published about that subject shows that spatial distribution of the heat flux values is highly heterogeneous. Maximum and minimum values of heat flux vary with different authors and method used, but all of them say that East Antarctic is characterized by low heat flux values (45-85 mW m-2) with the lowest values found especially in the central part. The values obtained in West Antarctic (65-180 mW m-2) and in the Antarctic Peninsula (maximum of 170 mW m-2). In the work whose data is used high values were obtained in the West Antarctic Rift system ( maximum value of 130 mW m-2). Some local geothermal anomalies have been reported such as Lake Wilhams (285 mW m-2) or Siple Dome (69 mW m-2). Elevated heat flux values are obtained in volcanic regions and in regions with relatively recent tectonic activity, in West Antarctic. The east Antarctic is characterized by low values, however the Coastal part of Queen Mary Land, the Lambert Rift and Victoria Land, show higher values, suggesting Cenozoic processes in the region, including volcanism or extension. Ice fusion occurs near the base of the ice sheet. In order to study this phenomenon 13 places were chosen from two profiles in WA and EA ( Martos, Y. et al, 2017) with data related to heat flux, sub glacial topography and ice thickness. An average thermal conductivity of 2.35 W K-1 m-1 and density of 917.5 Kg m-3 were used for the ice. Relations between the amount of molten ice per year due to the heat flux, the altitude and the thickness of the ice were obtained. The effect of temperature alteration at the surface in the temperature of the ice was calculate considering different modes of temperature variation, using an average value of 1.3 X 10-6 m2 s-1 for the thermal diffusivity of the ice. The results obtained show differences in the two regions studied but the heat flow values used were found from “Curie Depth Temperature” using an average value for thermal conductivity. Different thermal conductivity values could explain some of the discrepancies found. In addition, horizontal conduction of heat must be considered due to horizontal heterogeneities. All the models show that temperature variations occurred in a small interval of years can not be responsible for the fusion in the bottom of the ice sheet but the influence of a temperature raise at the end of the last glaciations can be detected at present.