Undergraduate Research and Creativity

URECA

2008-2009

Detecting the presence of Upper Circumpolar Deep Water
near Livingston Island, Antarctica

Andrea Tomasso and Joseph D. Warren
School of Marine and Atmospheric Sciences

A series of research cruises was conducted from 2004 through 2007 in the waters just north of Cape Shirreff, Livingston Island, Antarctica as part of an investigation into krill abundance in these nearshore waters. Cape Shirreff is home to several Antarctic fur seal rookeries and penguin colonies. Both of these animals rely on Antarctic krill as a primary food source for themselves and their offspring. This study sought to determine if circumpolar deep water (CDW) was intruding via deep submarine canyons into the nearshore area of Cape Shirreff. In other Antarctic areas, the upwelling of CDW has been linked to increased productivity. The nearshore area of Cape Shirreff was surveyed by three roughly-parallel transects which were conducted at least once each year during January or February. Transects included the western submarine canyon (Y2 transect), the eastern submarine canyon (Y8 transect) and shelf area between the two canyons (Y5 transect). Hydrographic data were collected using a SeaBird CTD which recorded a variety of parameters (including temperature, conductivity, dissolved oxygen) in one meter depth intervals from the surface to the shallower of 750 m or the bottom. Conductivity, temperature, and depth data were used to calculate salinity and density. Klinck et al 2004 defined the characteristics of CDW as salinities ranging from 34.6-34.74 PSU and temperatures ranging from 1-2 ^oC. Knowing this information, contour plots were created for density, salinity, dissolved oxygen, and temperature by transect and used to detect the intrusion of CDW. TS plots showed the presence of CDW at the bottom of some of the stations farthest from shore. The CDW signature was not detectable at any of the other stations in the transects most likely due to mixing of the water column. Surveys conducted in 2005-2007 detected a stronger CDW signature in the Y2 transect (western canyon) than in the Y8 transect (eastern canyon). We also examined the variability of the hydrography for years where we had multiple passes of each transect. This research was supported by the National Science Foundation?s Office of Polar Programs and the National Oceanic and Atmospheric Administration's Antarctic Marine Living Resources Program.