Dataset: floats_2003
Deployment: LMG0302

These isobaric floats were designed to repeat the following cycle: (a) sink to 250 db; (b) drift with the current at that level for 5 days; (c) sink to a greater depth 450-m and immediately begin an ascent to the surface, rapidly collecting temperature, conductivity and pressure data; (d) drift at the surface transmitting the environmental data and GPD position data using ARGOS. After completing this cycle the float sinks to 250-m to start the next cycle. Each float is equipped with a pumped Sea Bird temperature and conductivity sensor set and precision pressure sensor. The floats were deployed in a rough rectangular array centered over the deep trench running northwest from George VI Sound toward the shelf edge. The float deployment positions listed in Table 1.

Table 1. Float deployment times and positions

The tracks of the floats at 250 m indicated relatively small cross-self displacements during austral fall, less than 100 km from the inner-shelf deployment positions to the mid-shelf over 5 months. One float continued to send data during the winter, ice-covered period and returned to near its deployment position, thus completing a closed anticyclonic path about 50 km in diameter over 7 months. The 20-30 profiles of pressure, temperature and conductivity made during February through September 2003 by each float were used to estimate changes in heat and salt content over the WAP shelf during austral fall. The mid-shelf region had a surface mixed layer about 80-m deep above a deeper stratified region. The surface mixed layer lost heat at an average rate of 72 Watts/m2 (-0.6° C/mo) and gained salt at 166 gm/m2 /day (0.06 psu/mo). The stratified water between 80–250 m gained heat at an average rate of 31 Watts/m2 (+0.1° C/mo) and gained salt at 225 gm/m2/day (0.04 psu/mo). Thus the water column over the upper 250 m lost heat at a net rate of 41 Watts/m2 and gained salt at 391 gm/m2/day.

Four isobaric floats were deployed over the West Antarctic Peninsula (WAP) shelf near Marguerite Bay during February 2003 on cruise LMG03-02 to characterize the Lagrangian circulation and repeatedly profile the local hydrographic structure.