Table of Contents

• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Parameters
• Instruments
• Deployments
• Project Information
• Program Information
• Funding

Lagrangian Circulation on the West Antarctic Peninsula Shelf From Isobaric Floats

W. Owens, R. Limeburner, and R. Beardsley
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.

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.

Data format of time is decimal Julian days. Used Matlab gregorian.m to get the actual time, starting time at January 1, 4713 BC Greenwich time midnight, not noon.

No data for 7900029 is included here; the matlab file provided to BCO-DMO was corrupted.

The fundamental objectives of United States Global Ocean Ecosystems Dynamics (U.S. GLOBEC) Program are dependent upon the cooperation of scientists from several disciplines. Physicists, biologists, and chemists must make use of data collected during U.S. GLOBEC field programs to further our understanding of the interplay of physics, biology, and chemistry. Our objectives require quantitative analysis of interdisciplinary data sets and, therefore, data must be exchanged between researchers. To extract the full scientific value, data must be made available to the scientific community on a timely basis.

U.S. GLOBEC (GLOBal ocean ECosystems dynamics) is a research program organized by oceanographers and fisheries scientists to address the question of how global climate change may affect the abundance and production of animals in the sea.

The U.S. GLOBEC Program currently had major research efforts underway in the Georges Bank / Northwest Atlantic Region, and the Northeast Pacific (with components in the California Current and in the Coastal Gulf of Alaska). U.S. GLOBEC was a major contributor to International GLOBEC efforts in the Southern Ocean and Western Antarctic Peninsula (WAP).