Restriction of convective depth in the Weddell Sea

Abstract

The depth open-ocean convection can reach around Maud Rise in the Weddell Sea is estimated based on the entrainment assumption using hydrographic data obtained in winter 1986 during which no distinct polynya was observed. While the water column is stable at all CTD stations when observed, additional cooling makes the mixed layer water heavier than the underlying water at any depth in an adiabatic sense. However, convective plume cannot reach the ocean bottom since it loses positive density anomaly due to thermobaricity by entraining the Warm Deep Water (WDW) on its downward way. The deeper convection is located over Maud Rise where the maximum temperature of the WDW, θmax, is about 0.5°C while the shallower one in the warm water cell region where θmax is more than 1.0°C. The mean convective depth is much shallower than the ocean depth and the ventilated depth during the Weddell Polynya years (3∼4 km). Copyright 2007 by the American Geophysical Union.