Physical Oceanography Lunchtime Seminar, Spring 2019

12:30pm Wednesdays, OSB 425 (unless otherwise noted).

Seminar organizer: James Girton, girton (at), 206-543-8467.

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Date Speaker Institution Title Abstract
April 3 Paige Lavin (née Logan) UW Oceanography Random Forests in the Ocean: Using Machine Learning to Map Ocean Bottom Water Properties Bottom water properties are changing and making substantial contributions to ocean warming and sea level rise. While understanding these changes is important, a detailed, global analysis of the mean state of these water masses has not been undertaken since 1983. In this work, we analyze newer, more numerous shipboard hydrographic data using combination of the random forest regression algorithm and objective mapping to generate improved global maps of several bottom water properties. Maps of abyssal water properties are helpful for elucidating the complicated pathways these waters take throughout the global ocean. This analysis also demonstrates the skill of these machine learning procedures for mapping oceanographic variables.
April 10 Anda Vladoiu


Turbulence in the Western Mediterranean Sea The processes characterizing turbulence in the Western Mediterranean Sea were identified and quantified using microstructure measurements, revealing two types of contrasting dynamical regions. The mixing efficiency variability was investigated in the context of mechanically driven turbulence over a wide spectrum of turbulence intensities. The focus was on the Sicily Channel, a hotspot for turbulent mixing driven by a strong bathymetry constricted sheared flow and by internal wave breaking of tidal origin. Estimates of the vertical turbulent diffusive fluxes allowed for an assessment of the water mass property changes incurred in the channel.
April 17        
April 24 James Girton and Luc Rainville APL-UW

Robots Under Ice: Autonomous Forays Into the Dotson Ice Shelf Cavity

May 1 Stephen Monismith Stanford Flows over and through living roughness  
May 3 (Friday 10 am) Earle Wilson UW Oceanography Ph.D. Defense: Drivers of sea ice and upper ocean variability in the Southern Ocean  
May 8 Anna McLaskey UW Biological Oceanography Ph.D. Defense  
May 15 Sebastian Essink APL-UW Observing submesoscale flows in drifter pair dispersion

Submesoscale flows with length scales of O(0.1-20km) have a strong impact on the vertical structure of the ocean. They connect the surface ocean with the interior through ageostrophic, vertical fluxes and restratify the upper ocean by mixed layer instabilities and eddies. However, the role submesoscale flows play in the horizontal dispersion and re- distribution of tracers is yet to be understood; particularly, in the presence of the energetic mesoscale circulation.

In this talk, I analyze observed pairs of Lagrangian trajectories to characterize the turbulent dispersion at submeso-scales in the Bay of Bengal. Although the Bay of Bengal is host to active submesoscale flows, classic pair dispersion statistics, like the mean square pair separation, fail to capture those. The effect of the mesoscale strain field on the separation of pairs is dominant, even at the smallest resolved scales. In fact, the inferred mesoscale pair diffusivities are orders of magnitude larger than those attributed to the submeso- scales. We find, however, that the submeso-scale contribution to the dispersion at scales of O(0.1-20km) are non-trivial. Simulated drifters in satellite-derived, geostrophic flow fields are not capable of capturing the variability in observed trajectories. Even when attempting subgrid-scale stochastic parameterizations and accounting for near-inertial oscillations, we cannot reproduce the observed pair dispersion statistics. Reconciling the descriptive and dynamical characterizations of submesoscale flows is an important topic for understanding the impact of unresolved processes on modeled tracer dispersion.

May 20 (Mon 1pm) Sam Brenner APL-UW

Master's Defense:

The evolution of a shallow front in the Arctic marginal ice zone

May 22        
May 29 LuAnne Thompson UW Oceanography The effective depth of ocean-atmosphere interaction from monthly to interannual timescales  
June 3 (Monday 12:30pm) Sonya Legg Princeton Internal tide-driven mixing: Processes, parameterizations, and impacts  
June 3 (Monday 2pm) Brett Morris UW Oceanography M.S. Defense: Seasonality and forcing factors of the Alaskan Coastal Current in the Bering Strait from July 2011 to July 2012  
June 5 (Wednesday 1:30pm) Jake Steinberg UW Oceanography Geostrophic Turbulence and Eddy Vertical Structure: Deepglider Observations in the North Atlantic  


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