Abstract. Measurements of near-ice ( < 200 m) hydrography and near-terminus subglacial hydrology are lacking, due in large part to the difficulty in working at the margin of calving glaciers. Here we pair detailed hydrographic and bathymetric measurements collected with an autonomous underwater vehicle as close as 150 m from the ice-ocean interface of the Saqqarliup sermia-Sarqardleq Fjord system, West Greenland, with modeled and observed subglacial discharge locations and magnitudes. We find evidence of two main types of subsurface glacially modified water (GMW) with distinct properties and locations. The two GMW locations also align with modeled runoff discharged at separate locations along the grounded margin corresponding with two prominent subcatchments beneath Saqqarliup sermia. Thus, near-ice observations and subglacial discharge routing indicate that runoff from this glacier occurs primarily at two discrete locations and gives rise to two distinct glacially modified waters. Furthermore, we show that the location with the largest subglacial discharge is associated with the lighter, fresher glacially modified water mass. This is qualitatively consistent with results from an idealized plume model.
white sharks, which are presumably drawn to the island to feed upon pinnipeds, yet predation has 36 rarely been observed. In this study, an Autonomous Underwater Vehicle (AUV) was used to test 37 this technology as a viable tool for directly observing the behaviour of marine animals and to 38 investigate the behaviour, habitat use, and feeding ecology of white sharks off Guadalupe Island. 39During the period 31 October -7 November 2013, six AUV missions were conducted to track 40 one male and three female white sharks, ranging in estimated total length (TL) from 3.9-5.7 m, 41 off the northeast coast of Guadalupe Island. In doing so, the AUV generated over 13 hours of 42 behavioral data for white sharks at depths up to 90 m. The white sharks remained in the area for 43 the duration of each mission and moved through broad depth and temperature ranges from the 44 surface to 163.8 m (mean ± SD = 112.5 ± 40.3 m) and 7.9-27.1 °C (mean ± SD = 12.7 ± 2.9 °C), 45 respectively. Video footage and AUV sensor data revealed that two of the white sharks being 46 tracked and eight other white sharks in the area approached (n=17), bumped (n=4), and bit (n=9) 47 the AUV during these tracks. In this study, it was demonstrated that an AUV can be used to 48 effectively track and observe the behaviour of a large pelagic animal, the white shark. In doing 49 so, the first observations of subsurface predatory behaviour were generated for this species. At its 50 current state of development, this technology clearly offers a new and innovative tool for 51 tracking the fine-scale behaviour of marine animals. 52 53
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