IVARS: Dispatches from the Ice Edge

The IVARS project (for Interannual Variability in the Ross Sea) involves two cruises per year through the Southern Ocean: one in December during the spring phytoplankton bloom, and one at the end of the growing season in February. Cruises are scheduled to visit the same sampling sites during each of the project's five years. Cruises deploy from the U.S. McMurdo Research Station.

The 2005-2006 IVARS cruise took place aboard the R.V. Nathaniel B. Palmer, and is proceeding in cooperation with the multi-institution CORSACS project.

By comparing data from each cruise to that of "pre-bloom" water, IVARS researchers can calculate seasonal phytoplankton productivity and compare it to that of previous years, thereby revealing year-to-year changes.

During the December cruise, IVARS researchers deploy two moorings. Each has an elaborate suite of instruments designed to continuously sample the surface layer to reveal short-term variations within each growing season. The instruments are a fast repetition rate fluorometer (FRRF), a nitrate analyzer, a silicic acid analyzer, a whole-water sampler, two additional fluorometers, a sediment trap, thermistors, a CTD, and current meters. The moorings are retrieved during the second cruise.

IVARS scientists typically travel from the U.S. to Antarctica by flying to either Christchurch, New Zealand or Hobart, Tasmania, and then either flying aboard a LC-130 or C-141 cargo plane to McMurdo Station, or sailing across the Southern Ocean. The NZ-McMurdo flight takes 5-8 hours. The Southern Ocean transit typically takes about 8 days. Once the ship arrives at the ice edge, scientists are often ferried to McMurdo via helicopter.