Flow of warm Atlantic Water in the Norske trough on the East Greenland shelf

wilken-jon.von.appen [ at ] awi.de


Local water temperature increases associated with global warming have the potential to melt glaciers and ice sheets, which are major contributors to sea level rise. This Bachelor of Science thesis examines the flow of warm (0 ◦C – 2 ◦C) Atlantic Water (AW) in the Norske trough on the East Greenland continental shelf using an oceanographic section of CTD and ship-board ADCP (SADCP) data collected in June 2014. The Norske trough connects the open ocean to the marine terminating glacier Nioghalvfjerdsfjorden at 79.5◦ N and it is of interest whether warm water can flow through this trough to the floating ice tongue. The CTD data shows that AW with temperatures of 1.5 ◦C and salinities of 34.5 is overlain by Polar Water (PW) with temperatures of -1.5 ◦C and salinities of 31.5. The stratification is strong and the halocline is located at a depth of 100 m. The SADCP data was detided using the barotropic tidal model AOTIM5 and it shows that the flow reaches velocities along the trough of up to 0.15 m s−1 in the upper 250 m. The absolute geostrophic velocities calculated using the SADCP data, as well as the Rossby radius of 12 - 14 km calculated from the stratification, support the assumption that a bi-directional flow with an in- and outflow exists in the trough. Hence it is shown that warm AW reaches the Norske trough and flows into the direction of the 79.5◦ N glacier at a depth where it could potentially melt the glacier or its floating ice tongue. As a precursory step, it was attempted to calibrate lowered ADCP (LADCP) data in order to remove compass deviations that were assumed to be caused by a steel block in the vicinity of the CTD rosette. The data of both the upward and the downward looking LADCP were compared to the SADCP data in order to determine the compass deviation. It was found that in this case this method can- not be used to gain more information about the flow below 250 m depth because the compass deviations vary over time and between stations. It is proposed that this is due to the electromagnetic influence of coiled cables that were located close to the instrument.

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Heiderich, J. (2015): Flow of warm Atlantic Water in the Norske trough on the East Greenland shelf Bachelor thesis, Jacobs University Bremen and Alfred Wegener Institute.

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