Abstract
The Greenland ice sheet (GIS) is losing mass at an increasing rate due to surface melt and flow acceleration in outlet glaciers. Currently, there is a large disagreement between observed and simulated ice flow, which may arise from inaccurate parameterization of basal motion, subglacial hydrology or geothermal heat sources. Recently it was suggested that there may be a hidden heat source beneath GIS caused by a higher than expected geothermal heat flux (GHF) from the Earth’s interior. Here we present the first direct measurements of GHF from beneath a deep fjord basin in Northeast Greenland. Temperature and salinity time series (2005–2015) in the deep stagnant basin water are used to quantify a GHF of 93 ± 21 mW m−2 which confirm previous indirect estimated values below GIS. A compilation of heat flux recordings from Greenland show the existence of geothermal heat sources beneath GIS and could explain high glacial ice speed areas such as the Northeast Greenland ice stream.
Highlights
A recent notable increase in surface speed is observed in the northeastern region of Greenland originating from the center of Greenland ice sheet (GIS) and exiting through the ice-stream outlet glaciers; Nioghalvfjersbræ, Zachariæ Isstrøm and Storstrømmen[1]
The East Greenland margin extends for nearly 2000 km between 60°N and the Greenland Fracture Zone around 78°N12
The fjord is a sill fjord with a deep basin and penetrates ~90 km inland where it is connected to GIS by several land terminating glaciers[16,17]
Summary
The Greenland ice sheet (GIS) is losing mass at an increasing rate due to surface melt and flow acceleration in outlet glaciers. There were no indications of further major bottom water intrusions or deep convection in the period from 2006–2015 where θ and S below 240 m in average increased by 0.016 °C yr−1 and decreased by 0.03 psu per year, respectively During this period the highest potential temperature below 250 m was observed close to the bottom in the “Dybet” section and this temperature increase was manifested as a concave shape of the annual measurements in the θS-curve (Fig. 2c). The annual temperature increase of bottom water below 240 m depth could either be explained by a gradual bottom water renewal in the fjord system or due to internal processes in the “Dybet” section, i.e. turbulent vertical mixing and GHF. Elevated GHF providing heat for basal melt and, thereby, increasing glacier sliding over the bedrock could be a contributing factor local ice geometrical settings, subglacial hydrology and the mechanical properties of the ice-bedrock interface are important modulating factors
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