Environmental Dynamics Lab

Spotlights

Arctic Ocean layering — Given the ubiquity of layering in environmental stratifications, an interesting example being double-diffusive staircase structures in the Arctic Ocean, we have obtained exciting new results from a joint theoretical and laboratory experimental study investigating the impact of multiple layering on internal wave propagation. Results for a simplified model demonstrate the nontrivial impact of multiple layering, and utilizing a weakly viscous, linear model that can handle arbitrary vertical stratifications, we have performed a direct comparison of theory with experiments. The model has been applied to a case study of a staircase stratification problem obtained from the Arctic Ocean, showing a rich landscape of transmission behavior. A detailed report of this study will be shortly published in the Journal of Fluid Mechanics. [read more "Arctic Ocean layering"]
Lagrangian based methods for coherent structure detection — There has been a proliferation in the development of Lagrangian analytical methods for detecting coherent structures in fluid flow transport, yielding a variety of qualitatively different approaches. We have reviewed four approaches and demonstrated the utility of these methods via their application to the same sample analytic model, the canonical double-gyre flow, highlighting the pros and cons of each approach. Two of the methods, the geometric and probabilistic approaches, are well established and require velocity field data over the time interval of interest to identify particularly important material lines and surfaces, and influential regions, respectively. The other two approaches, implementing tools from cluster and braid theory, seek coherent structures based on limited trajectory data, attempting to partition the flow transport into distinct regions. All four of these approaches share the common trait that they are objective methods, meaning that their results do not depend on the frame of reference used. For each method, we also have considered a number of example applications ranging from blood flow and chemical reactions to ocean and atmospheric flows. A detailed report of this study has been published in Chaos. [read more "Lagrangian based methods for coherent structure detection"]
The formation and fate of internal waves in the South China Sea — For over a decade, studies have targeted the South China Sea, where the oceans’ most powerful known internal waves are generated in the Luzon Strait and steepen dramatically as they propagate west. Confusion has persisted regarding their mechanism of generation, variability and energy budget, however, owing to the lack of in situ data from the Luzon Strait, where extreme flow conditions make measurements difficult. The ONR IWSIE team, of which we were fortunate to be part of, have used new observations and models to (1) show that the waves begin as sinusoidal disturbances rather than arising from sharp hydraulic phenomena, (2) reveal the existence of >200-metre-high breaking internal waves in the region of generation that give rise to turbulence levels >10,000 times that in the open ocean, (3) determine that the Kuroshio western boundary current noticeably refracts the internal wave field emanating from the Luzon Strait, and (4) demonstrate a factor-of-two agreement between modeled and observed energy fluxes, which allows us to produce an observationally supported energy budget of the region. Together, these findings give a cradle-to-grave picture of internal waves on a basin scale, which will support further improvements of their representation in numerical climate predictions. A detailed report of this study has been published in Nature. [read more "The formation and fate of internal waves in the South China Sea"]

News Stories

From Cambridge, Mass. to Cambridge, UK — Andrew Rzeznik and Margaux Filippi will be participating in the 2016 Summer School for Fluid Dynamics of Sustainability and the Environment, in Cambridge, UK.
New group members — Welcome to our new group members! Dr. Alireza Hadjighasem, our new postdoc, will join us in August 2016 from ETH Zürich. He will work on Lagrangian Coherent Structures. Jade Coulin, a visiting student for the Fall semester, will join us from Ecole des Mines to work on sediment laden plumes in stratified environments with application to dewatering plumes from dee-sea mining. Keaton Burns and Andrew Rzeznik, PhD students at MIT, will be working with the group too [read more].
Deep Sea Mining — Prof. Peacock recently participated in the Ventbase 2016 June meeting in the Azores with a view to developing protocols for limiting the environmental impact of dewatering plumes generated by deep-sea mining activities. The group will prepare a working document to be distributed to the ocean community, including the International Seabed Authority.
Cruise around Palau — Prof. Peacock and Dr. Musgrave recently participated in a research cruise to Palau in the Pacific Ocean. They deployed PIES instruments to study internal waves as part of the FLEAT project [read more].
ONR Arctic Ocean Project — We have received new funding from the ONR to participate in the Stratified Ocean Dynamics of the Arctic (SODA) project. The project will involve procurement of Current and Pressure Recording Inverted Echo Sounders (C-PIES) with pop-up data telemetry capabilities. An array of between 6 and 11 instruments will be deployed across the Canada Basin and Chukchi Sea to monitor near-inertial wave activity and heat transport.
Ocean Hazards — We have received a new $3 million NSF Hazards-SEES grant to develop Lagrangian data analysis methods for the application to real world ocean hazards problems. This work will be a collaboration with WHOI, Virginia Tech., UC Berkeley, the US Coastguard and SINTEF, among others. The project will culminate with a field experiment off Martha’s Vineyard in summer 2018.
New papers — We have several new publications just published or coming out in journals such as the Journal of Fluid Mechanics and Physics of Fluids. Check out our publications page for more details.