Southern Great Barrier Reef physical oceanography cruises (SGBR Project 1989-1990)

A series of three oceanographic cruises were made to the southern Great Barrier Reef between 1989 and 1990. The cruise dates were:SGBR1: 23/8/1989 to 2/9/1989SGBR2: 15/10/1989 to 29/10/1989SGBR3: 19/2/1990 to 28/2/1990The instruments deployed during these cruises were:1. An array of tide gauges at Heron Island, Karamea Bank, Lady Elliot Island, Middle Island, North Reef, Perforated (Peak) Island Saumarez Reef and Gannett Cay.2. An array of current meters at Lady Elliot Island, North Reef, Saumarez Reef and Karamea Bank. 3. A weather station on Wistari Reef4. Drogues5. CTD and XBT profiles along transects and at moorings.6. Horizontal profiles The purpose of the study is to investigate mesoscale flow dynamics by observing the current, sea level and frontal structures of the region and to relate the changes observed to the physical forcings at the surface and horizontal boundaries. Over a period of 3 years cold water upwelling and entrainment features have been observed in AVHRR thermal imagery in the Capricorn channel during spring-time (September to December). Cool, saline water which exists on the narrow shelf south of the Capricorn channel apparently is upwelled or advected seaward just north of Heron Island and becomes entrained in the EAC. A mushroom jet-like feature has also been observed emerging from the coast between Cape Clinton and Bustard head. These features tend to be associated with relaxation or reversal of the prevailing SE trades and with weakening or reversal of the southward flow of the Eastern Australian Current (EAC).