ADELIE - Antarctic Drifter Experiment: Links to Isobaths and Ecosystems

• Main Authors: Thompson, Andy, Castro Morales, Karel, Chapman, Graham, Grant, Hazel, Heywood, Karen, Jullion, Loic, Kaiser, Jan, Luijting, Hanneke, Matthews, Adrian, Mountifield, Dougal, NaveiraGarabato, Alberto, Nunes, Nuno, Renner, Angelika, Screen, James, Singhruck, Patama, Trasviña Castro, Armando, Trevett, Doug
• Format: Report
• Language: unknown
• Published: 2007
• Subjects: Antarctic; Antarctic Peninsula; Kerguelen; Kerguelen Island; The Antarctic; Weddell; Weddell Sea; Antarc*; Antarctica; Ice Shelf; Ice Shelves
• Online Access: https://authors.library.caltech.edu/81840/; https://authors.library.caltech.edu/81840/1/ADELIECruiseReport.pdf; https://resolver.caltech.edu/CaltechAUTHORS:20170926-132516497

The goal of the ADELIE research project is to map, for the first time, the near surface currents around the tip of the Antarctic Peninsula and to determine the role of these currents in the retention or dispersion of krill. Specifically, we will test the hypothesis that pathways to the west near the continent link current systems on the western and eastern sides of the the Peninsula. The influence of bathymetry controlling the splitting and steering of these frontal jets will also be studied. Data for the ADELIE project was collected during cruise JR158. We seek to resolve two important features of the current system around the margin of Antarctica, the Antarctic Slope Front and the Antarctic Coastal Current (see schematic in Figure 1). These currents both flow westward around the continent and are important for the transport of krill, for preconditioning the shelf waters, for the formation of Antarctic Bottom Water, and for supplying waters beneath ice shelves thus melting the underside of the ice shelf. The Antarctic Slope Front defines the boundary between cold, fresh waters filling the Antarctic continental shelf, and the warmer, more saline waters further offshore and is identified by a strong horizontal gradient in temperature and salinity. The Antarctic Coastal Current is a fast, shallow flow over the continental shelf often associated with the front of the ice shelf. The Coastal Current and the Slope Front may merge where the shelf is narrow, but over broad regions of the continental shelf the flows split into two distinct systems. The study area for JR158 is from the tip of the Antarctic Peninsula across the continental shelf and slope to the east and into the deep Weddell Sea (Figure 2). A CTD and Lowered ADCP section were conducted along this transect moving from east to west. This transect was selected to complement the western end of the WOCE SR4 time series, repeated annually by Eberhard Fahrbach and colleagues at the Alfred Wegener Institut (AWI) during the 1990’s. Due to the complexity of the topography in this region, Eulerian measurements at one site are not necessarily representative of the current system a short distance away. Therefore we also deployed surface drifters and Lagrangian floats as a means of tracking the currents. While surface drifters have been successfully released near the Antarctic continent during previous cruises, these drifters provide the first Lagrangian measurements of the current system on the eastern side of the Antarctic Peninsula. New instruments were also tested during JR158 including a microstructure profiler and a dissolved gas mass spectrometer. The microstructure profiler, which is used to resolve smallscale diapycnal mixing, will be used extensively during a mixing study near Kerguelen Island in 2008. The mass spectrometer measures dissolved oxygen/argon ratios that allow estimates of net community production over larger spatial scale with high temporal resolution.