Palmer LTER Lagrangian Current Measurements

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Satellite-tracked drifters provide simple yet powerful tools to track the motion of near-surface water on time scales ranging from the tidal/inertial band to monthly and longer. The research described herein will deploy satellite-tracked surface drifters during the annual austral summer Palmer Long Term Ecological Research (LTER) cruises in January 2006 and 2007 in order to investigate the nearsurface Lagrangian currents over the western Antarctic Peninsula (wAP) shelf. This region is experiencing the highest surface air temperature increase (roughly +0.06 degrees C per year) in Antarctica, and LTER and other investigators have found that ecosystem responses to the rapid warming and sea ice decline are already apparent at all trophic levels from phytoplankton to penguins. Building a better understanding of the regional circulation and its variability seems an essential component to understand existing physical and biological processes and longer-term changes in this important and sensitive Antarctic ecosystem. These new Lagrangian measurements will complement those made during the 2001-2003 U.S. Southern Ocean (SO) GLOBEC program and provide the first detailed look at the near-surface flow in this important section of the wAP shelf. In particular, the combined 3-year LTER Lagrangian measurements should identify (a) the source region(s) of the buoyant coastal current discovered flowing southwest along the outer coast of Adelaide Island and into Marguerite Bay during SO GLOBEC and (b) if organized cross-shelf flows occur that help create a two gyre circulation over the shelf as suggested by Hofmann et al (1996) based on regional hydrography. The principal investigators will process and analyze the LTER 2005-2007 drifter data and collaborate with Palmer LTER investigators on the interpretation and integration of the Lagrangian data with their studies. The edited data, analysis results, and animations of the drifter data with surface weather data will be posted on the LTER website for use and viewing by scientists, students, and the public. Results will be presented at national meetings and published in referred journals.