Mapping the kinematics and dynamics of tidal ocean currents with surface drifters
I am the lead-PI of this NSF-funded project, in collaboration with Ed Zaron from Portland State University, and Rick Lumpkin from the NOAA Atlantic Oceanographic Meteorological Laboratory. This project will generate new knowledge concerning tidal currents in order to better understand tidal dynamics and their role in the maintenance of the global thermohaline ocean circulation. The drifter dataset that will be utilized to investigate baroclinic tidal phenomena is both large enough and unique (in terms of time span, geographic coverage, and accuracy) to provide a quantitative description of tidal properties. In addition, qualitative and potentially new assessments of tidal/non-tidal interactions will be obtained, including their seasonal and longer temporal variability. A novel decomposition of the tidal energy budget, which separates processes primarily affecting phase-locked and non-phase-locked tidal signals, is proposed to guide the analysis and interpretation of not-only the drifter observations, but also observations from altimetry and numerical simulations which will be used alongside the drifter data.
The Agulhas System Climate Array (ASCA)
I am a co-PI of the Agulhas System Climate Array (ASCA) project, led by Prof Lisa Beal and funded by the U.S.A. National Science Foundation (NSF) for its US component. More broadly, ASCA is an international research project with partners from South Africa, the USA, and the Netherlands, with funding support from the South African Departments of Science and Technology (DST) and Environmental Affairs (DEA), the US National Science Foundation (NSF) and the Royal Dutch Institute for Sea Research (NIOZ). It is designed to provide long term observations of Agulhas Current volume, heat and salt transport and its variability from mesoscale (eddies), through seasonal to interannual timescales. This is achieved by means of two shelf and seven full-depth tall moorings, interspersed with five Current- and Pressure-recording Inverted Echo Sounders (CPIES), measuring pressure, current velocities, temperatures and salinities. The ASCA shelf and tall moorings extend 200 km offshore along the descending TOPEX/Jason satellite ground track #96, through the core of the Agulhas Current, with CPIES measurements extending the array to 300 km offshore.
Global Observational Constraints on Oceanic Response to Wind Forcing
I am leading this NSF-funded collaborative research project with Dr. J.M. Lilly from Northwest Research Associates and Dr. R. Harcourt from the Applied Physics Laboratory of the University of Washington. The goal of this project is to better understand the dynamics of the ocean surface boundary layer through the first global study of the wind stress to ocean current transfer function. This is to be accomplished by analyzing in detail the response to wind forcing in the global array of surface drifters, which sample the ocean currents in the vicinity of their 15 m drogue depth. The global analysis is to be informed and tested by (i) a prototype study from the SPURS region, near a well-instrumented air-sea flux mooring, and (ii) analysis of synthetic data generated with a recently improved turbulence closure model that explicitly includes Langmuir turbulence. The hypotheses that wind, wave, and stratification state substantially modify near-surface mixing will be tested by examining dependencies of the transfer function on various environmental parameters, such as Langmuir number. Observed patterns will then be interpreted and scrutinized by deriving new theoretical approximations to the expected transfer functions characterizing different mixing processes.
An new global hourly surface drifter dataset
I have produced with colleagues at AOML and NorthWest Research Associates a new global surface drifter dataset at hourly resolution. This dataset is freely available through the Global Drifter Program Data Assembly Center hosted at NOAA/AOML in Miami, FL. The dataset is described in Elipot S., R. Lumpkin, R. C. Perez, J. M. Lilly, J. J. Early and A. M. Sykulski (2016), A global surface drifter dataset at hourly resolution, doi:10.1002/2016JC011716. This on-going project is funded through The Cooperative Institute for Marine and Atmospheric Studies (CIMAS).