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Webinar: Kinematics and dynamics of oceanic overflows: Denmark Strait as a case study

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Thursday, 09 September 2021, 2:00

Thursday, September 9, 2021. 2:00 PM. Webinar: Kinematics and dynamics of oceanic overflows: Denmark Strait as a case study. Atousa, Saberi, Johns Hopkins University. Sponsored by NOAA and Johns Hopkins University. More information here. Attend here.

Oceanic overflows contribute to the deep branches of the thermohaline circulation. The Denmark Strait Overflow (DSO) is a prime example of an important deep overflow that feeds the North Atlantic Deep Water (NADW) to form the lower limb of the Atlantic meridional overturning circulation (AMOC). Determining DSO pathways and monitoring its fluxes is critical to estimating the state and variability of the AMOC and hence the North Atlantic climate system. This study traces the upstream pathways and along-pathway changes in its water properties, using Lagrangian backtracking of the DSO sources in a realistic numerical ocean simulation. The Lagrangian trajectories confirm the previously known pathways from the north and reveal additional pathways from the south of Iceland. The southern pathways supply over 25% of the DSO during winter of 2008 when the North Atlantic Oscillation (NAO) index was positive. The southern pathways mark a more direct route from the near-surface subpolar North Atlantic to the NADW. To elucidate the formation mechanism of these pathways, we also explore the dynamics of overflow pathway partitioning and the effect of upstream reservoir on overflow production for a canonical sea-strait geometry in an idealized model. We use rotating hydraulic theory and a 1.5-layer shallow water model to reveal the relation between reservoir conditions, strait geometry, and overflow transport. Results revealed that the hydraulically controlled flow in the strait is nearly independent of basin circulation regardless of the parabolic curvature. However, the basin circulation intrudes more into the channel for wider parabolas. The results also uncovered interesting physics that are useful for prediction of overflow transport for a more realistic channel geometry.

Bio(s): Atousa Saberi holds a bachelors' in mechanical engineering, and a masters' in ocean engineering. For her master's thesis, she worked on developing a storm surge hindcast simulation of hurricane Sandy using ADCIRC model and studied the effect of storm surge on the Indian River Lagoon estuary in Florida. Atousa is in her last year of PhD at Johns Hopkins Earth and Planetary Science Department studying the deep overflows and their potential role in the climate system. Atousa also enjoys teaching and science communication. She was awarded a fellowship to design and teach an undergraduate course on natural hazards. She is now considering a postdoctor

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