POAC 09 - Bedford Institute of Oceanography

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Fig. 6. Trajectories of ice beacons deployed on ice island between 15 Sept and 18 Nov 2008. The blue line represents the Argos ice beacon and the red line represents the Iridium GPS beacon. Fig. 7. Six-hourly wind velocity at 75°N, 82.5°W (top panel), and velocity of ice island (bottom panel). Plots of the latitude and longitude show that ice island stopped suddenly on day 266 and remained stationary for about 1 day (22-23 Sept), suggesting it grounded (Fig. 8). The GPS data
is superimposed on a contour map of bathymetry, derived from a combination of gridded IBCAO (International Bathymetric Chart of the Arctic Ocean) data and multi-beam data. From Fig. 9, the water depth at the apparent grounding site was about 100 m, however soundings shown on hydrographic charts for the area are sparse. When the winds shifted from northwesterly to northeasterly on day 267, the ice island entered Jones Sound through Glacier Strait, where the bathymetry suggests the ice island had a draft of less than 60-70 m. Thus the apparent grounding site probably represents a rise not captured in the bathymetry data. A draft of less than 60-70 m is consistent with altitude measurements of the front of the Petermann Glacier, which imply a draft of about 35 m along most of the front (Higgins, 1991). Fig. 8. Hourly latitude and longitude from the Iridium GPS beacon. The ice island then drifted westward into Jones Sound where it remained for about 6 weeks, making several clockwise loops within the eastern end of the sound. A multiple regression model was used to compare the wind and iceberg velocities, with the iceberg velocity component as the dependent variable and the wind components as the independent variables. The multiple correlation component for the u (eastward) component (R=0.40), is higher than for the v (northward) component (R=0.22), probably because of topographic effects on winds in the sound, which is oriented in an east-west direction. The regression coefficients for the iceberg u component imply the iceberg is drifting at 2.8% of the wind speed and 16 degrees to the right of the wind. However for the iceberg v component, there is negligible correlation with the wind v component.
Page 1 and 2: POAC 09 Luleå, Sweden Proceedings
Page 3 and 4: across Nares Strait adjacent to the
Page 5: the ice island. A photograph of the
Page 9 and 10: CONCLUSIONS AND DISCUSSION Understa

POAC 09 - Bedford Institute of Oceanography

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