Summary

The USCGC Glacier was used for a science cruise in the Ross Sea during February 1987. The cruise was provided for two groups from Rice University (Houston, Texas) led by Dr. J.B. Anderson and included three people from Victoria University.

In the first part of the cruise (5-15 February) a seismic and sedimentological programme was undertaken in the Cape Hallett region. The aim of this study was to investigate sediment transport in several large submarine channels that cross the region with subsequent deposition in the basins to the north. Two parallel single channel seismic reflection and bathymetry profiles 150 nautical miles long and 30 nautical miles apart were run ESE from Cape Hallett using a 8.6 kJ sparker system. Piston cores approximately 15 nautical miles apart were taken along the profiles, using a corer with 3 m long barrel.

In the second part of the cruise (15-20 February) the programme concentrated on the McMurdo Sound area with S-216 joining the USCGC Glacier.

Seismic, bathymetry and piston coring transects were undertaken in the Cape Royds area to determine how sediment was moving over the sea floor of this area to the 900 m deep Erebus basin offshore. Bathymetric surveys of the inshore area were carried out using the Arctic Survey Boat and VUWARC echosounder and revealed several small canyon-like features running offshore.

A seismic line was run across McMurdo Sound to intersect the CIROS-1 site and lines were also run in the New Harbour-Marble Point area to study sediment accumulation in sea floor depressions of this area.

A major part of the S-216 programme was to recover a large sediment trap (collecting area = 1M²) deployed from the fast ice edge in 520 m water depth in early December 1986. The position of the trap was determined by Brian Andersen (NZ Lands and Survey) soon after deployment. The surveying and geographical back sights in combination with accurate bathymetry were crucial to the later successful recovery of the trap. The Navsat position determined on the USCGC Glacier proved to be at least 2.5 km west (shallower) than the trap recovery position.

The trap mooring consisted of subsurface floats, trap and an acoustic release that was ranged and released from a portable deck unit installed in the small boat independent of the icebreaker. Once the mooring was released a helicopter was used to locate the floats and the small boat then secured the trap mooring for pickup by the icebreaker's main crane.

A seismic line was also attempted in Granite Harbour to determine the nature of sediments "ponded" in the inner and outer basins of the harbour. Dense pack ice was encountered while running the lines which resulted in poor quality records.