Vertical Fine Structure Beneath the Ice of the Western Antarctic Peninsula Shelf

in Austral Winter, 2001

Jason Hyatt¹, Robert Beardsley¹, John Klinck², Eileen Hofmann²

¹Woods Hole Oceanographic Institution

²Center for Coastal Physical Oceanography, Old Dominion University

As part of the U.S. Southern Ocean GLOBEC program, a broad-scale CTD survey was conducted in Marguerite Bay and the adjacent West Antarctic Peninsula shelf during austral winter (July 22 to August 31, 2001). With sea-ice covering most of the study area and eliminating almost all surface wave motion, the R/VIB Nathaniel B. Palmer provided a very stable platform, allowing high-quality CTD data to be collected without significant wave-induced contamination. Many of the CTD profiles exhibit a 93steppy94 structure in the main pycnocline. These steps are thin in the vertical, of the order of a few meters, and are separated by stratified layers that ranged in thickness from a few to tens of meters. In this region, very cold winter surface water overlays warmer, more saline Antarctic Circumpolar Deep Water, such that both temperature and salinity increase with depth. The structure of these steps will be described in detail, and some possible causes will be presented.