Jonathan Nash

Jonathan Nash

Surface tides are the heartbeat of the ocean. Because they are controlled by Earth’s motion relative to other astronomical objects in our solar system, surface tides act like clockwork and generate highly deterministic ebb and flow familiar to all mariners. In contrast, baroclinic motions at tidal frequencies are much more stochastic, owing to complexities in how these internal motions are generated and propagate. An analysis of current records from continental margins worldwide illustrate that coastal internal tides are largely unpredictable. This conclusion has numerous implications for coastal processes, as across-shelf exchange and vertical mixing are, in many cases, strongly influenced by the internal wave field.

Above: a northern hemisphere perspective on the predictability and strength of the internal tide on coastal shelves. Each inset plot shows detailed bathymetry and mooring locations along the western US coast, eastern US coast, and UK coast. Bar plots for each mooring show the RMS barotropic velocity, baroclinic velocity, and 90-day harmonic fit to the baroclinic velocity (H90), which we consider to be the predictable part of the signal. The magnitude for the barotropic component is given in cm/s (all plots use the same 0−20 cm/s range). The skill of the 90-day harmonic fit is indicated in the upper-right corner of each panel as a percentage.

Related Publications:

The unpredictable nature of internal tides and nonlinear waves on continental shelves. J. Phys. Oceanogr., 42, doi: 10.1175/JPO-D-12-028.1, 2012 (Nash, J.D., S.M. Kelly, E.L. Shroyer, J. N. Moum, and T. F. Duda) [pdf]

Are any coastal internal tides predictable? Oceanography, 25(2) 80-95. (J.D. Nash, E.L. Shroyer, S.M. Kelly,M.E. Inall, T.F. Duda, M.D. Levine, N.L. Jones, and R.C. Musgrave) [pdf]

Nonlinear internal waves over New Jersey’s continental shelf. J. Geophys. Res., 116, C03022, doi:10.1029/2010JC006332,2011.(E.L. Shroyer, J.N. Moum and J.D. Nash) [pdf]

Energy transformations and dissipation of nonlinear internal waves over New Jersey’s continental shelf. Nonlinear Proc. Geophys., 17, 345-360, 2010 (E.L. Shroyer, J.N. Moum, and J.D. Nash) [pdf]

Mode 2 waves on the continental shelf: Ephemeral components of the nonlinear internal wavefield. J. Geophys. Res., 115, C07001, doi:10.1029/2009JC005605, 2010 (E.L. Shroyer, J.N. Moum, and J.D. Nash) [pdf]

Vertical heat flux and lateral mass transport in nonlinear internal waves. Geophys. Res. Lett., doi:10.1029/2010GL042715, 2010 (E.L. Shroyer, J.N. Moum, and J.D. Nash) [pdf]

Observations of polarity reversal in shoaling nonlinear internal waves, J. Phys. Oceanogr., 39, 691-701, 2009, 2009 (E.L. Shroyer, J.N. Moum, and J.D. Nash) [pdf]

NLIWI/SW06 was a 5-year interdisciplinary study funded by the Office on Naval Research.

Internal Tide and NonLinear Wave Variability on Continental Shelves