Near Inertial Shear and Kinetic Energy in the North Atlantic Experiment (NISKINE) Departmental Research Initiative

Motivation

Motions with near-inertial frequency dominate upper ocean shear and substantially contribute to upper ocean turbulence. However, many features of their generation, evolution, and decay remain unconstrained. Time-variable wind stress generates currents at or close to the local inertial frequency. Some of this energy is lost to shear-driven turbulence at the mixed-layer base, while some has been observed to radiate downwards and laterally in the form of propagating low mode near-inertial internal waves (NIWs). The generation and evolution of high-mode NIWs, with their associated shear and turbulence is poorly understood.

Recent theoretical, numerical and observational studies have pointed to a potentially prominent role for NIW interaction with mesoscale and submesoscale features. Mesoscale and submesoscale vorticity, strain, and shear may play a role in NIW propagation, evolution, refraction, dissipation, and energetics more generally. NISKINE will involve a synthesis of both ship-based and autonomous-platform based observational work, numerical studies and theoretical analysis to investigate NIW generation, evolution, and dissipation in the upper ocean over inertial to seasonal timescales. The target observational area will be the North Atlantic, north of the Gulf Stream/N. Atlantic Current, a region of with enhanced mesoscale ocean variability and strong atmospheric forcing.

Objectives

  • Investigate factors controlling near-inertial energy input, which may include subtleties of the mixed layer, the submesoscale, and the adjustment/breakdown associated with strong lateral variability.
  • Assess the importance of non-wind-source NIWs in the upper water column, both in terms of energy and shear.
  • Explore the near-surface decay and subsequent vertical/lateral propagation of NIW energy. This maybe influenced by linear or nonlinear interaction with mesoscale and submesocale features, other internal waves, or physical mechanisms that have yet to be fully appreciated.
  • Understand the dominant physical processes that control the intensity and distribution of associated turbulent mixing.
  • Use accrued dynamical insight to refine parameterizations of upper ocean shear, whether deterministic or stochastic, for use in regional or global forecast models.

Approach

The program will draw upon and advance knowledge obtained under the ONR sponsored Lateral Mixing program, the Non-Linear Internal Waves program, and other programs that utilized a parallel process between developing theory, models, and parameterizations and using field and observational programs to test these developments as hypothesis. The program will invest largely in the observational efforts but will include theory, model, and parameterization developments as well. The novel use and improvement of autonomous sampling instrumentation that can survive the difficult seasonal conditions of the North Atlantic are of interest.

Request for Planning Letters

The first step in the DRI process is for prospective investigators to prepare planning letters. The purpose of the planning letters is to allow investigators to submit a short (three pages maximum) summary of their ideas on this topic for ONR to evaluate, provide technical feedback and indicate whether a full proposal would have a reasonable chance of success.

Important Dates

July 31, 2017: Last date to submit planning letters (submit by email)
August 31, 2017: Last date ONR will respond to all submitted planning letters and requests for proposals
October 30, 2017: Nominal due date for encouraged proposals
November 30, 2017: Earliest anticipated commencement of awards made with FY18 funding - dependent on USG budgetary process

All planning letters should be submitted by email to:

Dr. Terri Paluszkiewicz (terri.paluszkiewicz@navy.mil)

Please use the following naming convention in your email submission: NISKINE planning letter from "Your Name" in your email subject line. If you do not receive a thank you note within 10 days, please follow-up with a resend. If you do not receive a response by August 31st, please send an inquiry by email.

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