Maud Rise revisited

An oceanographic field program called the Antarctic Zone Flux experiment was carried out in the eastern Weddell Sea during austral winter (July-September) 1994. Data from a drift buoy array were used in concert with shipboard observations to provide exceptionally high horizontal resolution of upper ocean hydrographic parameters near Maud Rise. Chemical and tracer data were obtained from the ship. We identify a "warm pool" southwest of the rise as a dynamically necessary region of positive (cyclonic) vorticity that is associated with a Taylor column over the rise. Both a warm "halo" surrounding the Taylor column and the warm pool are associated with thermocline shoaling that is a necessary condition for high upward heat fluxes to occur. These features extend the influence of Maud Rise bottom topography on upper ocean heat flux over a region that is larger, by a factor of at least 2, than the area directly overlying the rise. Areal mean upward heat fluxes of about 25 W m(-2) are derived using both upper ocean T ("instantaneous") values and tracer data ("integrated") values. Fluxes derived over the warm halo and pool regions using only upper ocean T exceeded 100 W m(-2) at specific sites. Elsewhere in the region, the T-derived heat fluxes varied widely from <10 to >50 W m(-2), whereas the tracer-derived heat fluxes showed a considerably more uniform distribution. Our mean values are similar to those that have been previously reported. Historical ice cover data have shown that the geographical region encompassed by Maud Rise and the warm pool area to the southwest is a preferred site for polynya formation, consistent with these findings. Time series analyses of the historical upper ocean data set suggest that conditions conducive to polynya formation are correlated with climate processes remote from the Southern Ocean.