Site 2.

This site was the most westerly site occupied on the northern side of the glacier tongue (708 334.6 m N, 277 619.7 m E), as close as possible to the "change in slope" of the main ice flow. An embayment in the tongue has formed because the edge of the ice is slowed in velocity by a sub ice basement high creating a small icefall on this north side of the tongue.

Figure 1. Sketch map and cross section of the Mackay Glacier Tongue showing positions of ROV dive sites and interpretation of the sea floor grounding zone along the ice tongue axis.

The glacier tongue at this site is grounded approximately at 100 m depth although local edge rebound exposes areas of the sea floor under the ice cliffs. Ridge and trough relief on the sea floor trends across glacier showing active coupling of the sea floor and moving glacier tongue. Sedimentation is active with mud drapes on boulders and ice contacting the sea floor was observed in several places. No significant conductivity or temperature change in the water column or at the ice contact were measured confirming the absence of measureable meltwater discharge. Encrusting benthos was generally absent indicating much more active sedimentation than at site 1. The basal debris layer (alternating layers of debris rich and poor ice) in the tongue was 20m thick.