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Center for Nonlinear Studies |
Dense shelf water (DSW) is formed in coastal polynyas around Antarctica as a result of intense cooling and brine rejection. A fraction of this water reaches ice shelf cavities and is modified due to interactions with sub-ice-shelf melt water. This modified water mass contributes to the formation of Antarctic Bottom Water, and consequently, influences the large-scale ocean circulation. In the first part of the talk, a variety of numerical experiments performed with hydrostatic and non-hydrostatic models will be presented. These experiments identify two previously unknown processes that may occur in Antarctic DSW outflows: 1) topographic vorticity waves whose properties show an important connection with ambient stratification, buoyancy force exerted by the outflow and along-slope flow magnitude; and 2) flow splitting, where part of the dense current detaches and flows into the stratified interior as an intrusion, while the remainder continues to flow to the bottom of the ocean. The second part of the talk will focus on the role of sub-ice-shelf melting in the formation and export of DSW in idealized ocean/sea-ice simulations coupled with a thermodynamically active ice shelf. Preliminary analysis from a set of experiments with variable horizontal grid resolutions, ice shelf geometries and atmospheric forcing will be presented. In all simulations DSW is spontaneously formed in coastal polynyas due to the combined effect of the imposed atmospheric forcing and the ocean state. These results show that sub-ice-shelf melting can significantly change the rate of dense shelf water outflows, highlighting the importance of this process to correctly represent bottom water formation.
Host: Milena Veneziani