Observed Mixing at the Flanks of Maud Rise in the Weddell Sea. Issue 8 (16th April 2022) - Mohrmann, M.
Abstract: Maud Rise is a seamount in the eastern Weddell Sea and the location of polynyas and a persistent halo of reduced sea ice. We present novel in situ data from two profiling floats with up to daily resolved hydrographic profiles in this region. The water properties below the mixed layer of the Maud Rise region are significantly correlated with bathymetric depth; thus, the Maud Rise flank defines the front between the Warm Deep Water of the abyssal ocean and the colder Taylor cap over Maud Rise. We analyze the spiciness curvature in density space to quantify the observed frequency or magnitude of intrusions, which are substantially increased along the flanks of Maud Rise. These intrusions are indicative of enhanced lateral and vertical mixing along heavily sloping isopycnals, creating favorable conditions for thermobaric and double diffusive convection and likely facilitating the formation of the Maud Rise halo and polynyas. Plain Language Summary: The cold, dense water atop the Maud Rise seamount in the Southern Ocean is separated from the warmer mean flow of the Weddell Gyre by an effect called a Taylor column. At the northern flank of Maud Rise, we observe a front between these water masses. Due to the water masses' difference in temperature, salinity, and density, across‐front intrusions are accompanied by vertical transports and mixing processes. These can possibly explain previously observed local melting of the sea ice along the flanks of Maud Rise. Key Points: High frequency (1–3 days) float profiles were collected over both Maud Rise and its vicinity over several seasonal cycles Temperature and salinity below the mixed layer are strongly bathymetry‐dependent at Maud Rise Enhanced spiciness variability indicates intrusions and mixing between Maud Rise Deep Water and the surrounding Warm Deep Water