Since 1993, each year during Austral summer (Jan-Feb) Palmer LTER has a 38 day oceanographic cruise to observe ecological conditions along the west Antarctic Peninsula. The focus of operations is the LTER sampling grid, a 700 x 200 km region extending from Palmer Station on Anvers Island in the north to Charcot Island in the south, and from the nearshore zone to the open sea beyond the continental shelf. Most of this region is now free of sea ice cover in the summer period. We recently extended the study region farther south to include an area with persistent summer sea ice. There are 22 scientists on the cruise who observe ocean physics, chemistry and ecology. The main emphasis is on the Antarctic marine food web including nutrients, bacteria, phytoplankton, krill, salps and penguins.

During the 28-day science part of the cruise we occupy a series of hydrographic stations at defined locations on the sampling grid. A large number of measurements is made at each station, taking about 6 hours per station. These measurements provide an annual snapshot of summer conditions from which we can look for trends or changes from year to year.

We also conduct other operations during the cruise. We spend three days each at three selected locations in the north, central and southern areas of our grid, to conduct special experiments looking at specific ecological processes. For example, we will use the Slocum Glider to create 3-dimensional maps of water properties in the penguin foraging region to the south of the colony on Avian Island. We also retrieve a sediment trap from a location in the north, which collects samples of settling particles over the whole year. The trap is in place for the next 12 months. Finally, the penguin team will spend 5 days on Avian Island counting penguins and measuring breeding success. We also visit our colleagues at the British Rothera Station on Adelaide Island.