Where AUVs Dare: Svalbard’s subglacial discharge plumes
The summer melt season in the Arctic is getting longer and warmer, and this is accelerating the rate of mass loss from glaciers and ice sheets in the region. It is against this backdrop that detailed observations of sea and land ice are necessary as all this stored ice in the cryosphere plays a large role in regulating the climate. It is important that we understand the ways in which this melting ice will change the modern world – be that through sea-level rise, changing ocean currents or increasingly unpredictable anomalous weather.
Recent research has linked increasing ocean temperatures to rising melt or ablation rates. Two types of water (fractions) can originate in this process and can be tracked by linear mixing lines along temperature and salinity gradients; one is freshwater discharge from the base of the glacier and the other results from direct submarine melting due to warm fjord waters. Due to the difficulties of direct observation at a glacier face, most studies rely on mathematical models using plume theory and these studies indicate that subglacial discharge plumes can enhance submarine melting at the glacier through both friction and by drawing in warmer fjord water.
This project aims to use novel AUV technology to gain direct observations of these subglacial discharge plumes which form during the melt season. They occur when fresh, cold meltwater runs into the fjord through channels at the bottom of the glacier. This meltwater enters the fjord and forms a buoyant plume that rises towards the surface, and the turbulent nature of this plume results in entrainment and affects the circulation of the fjord. Temperature and salinity measurements are used to identify the presence and dynamics of the plume by fractions of entrained fjord water, discharge and the submarine meltwater.