Seasonal variability of bottom water properties off Adélie Land, Antarctica

Abstract

The region off Adélie Land is considered as one of the sources of Antarctic Bottom Water. Hydrographic observations were carried out during two cruises in December 1994 and January 1995 and January and February 1996 in this region. Vertical sections along 140°E show that bottom water is colder and fresher than the water above. This bottom water also has higher dissolved oxygen and lower silicate concentrations. The saline bottom water that originated from Ross Sea is not found in these hydrographic data obtained west of 142°E. Current meter moorings were also carried out at three locations on the continental slope in this region. At one of these moorings (139°59′E, 65°10′S, 2665 m deep), data were successfully obtained from January 1995 to March 1996. Three current meters were deployed at 1075, 1778, and 2632 m deep in this mooring. The data show that the average current speed at the lower current meter is 16.2 cm s−1, and it is about 3 times larger than those at the upper two current meters. Also, variability of speed and temperature is largest at the lower current meter. In addition, seasonal variability of speed and temperature is evident only at this current meter. From August to December, speed is larger by 5.7 cm s−1 and temperature is lower by 0.27°C. Also, their variability is larger during the same period. This seasonal variability observed near the bottom suggests seasonal variability of bottom water formation in this region.