NIOZ is part of the Netherlands Organisation for Scientific Research (NWO)

Koninklijk Nederlands Instituut voor ZeeonderzoekRoyal Netherlands Institute for Sea Research

Spectral slopes and peaks: moored observations of internal waves in the ocean

Hans van Haren

Internal Wave Band –GM--continuum

Garrett and Munk (1972) model internal waves:

Simplified density model

Smooth, horizontal, reflecting sea floor

No tides, nonlinear effects, current shear, horizontal Coriolis, etc.

Kinematics: N-scaling spectrum?

Internal wave ‘continuum’:

Depends on smoothing: no deep gaps? Above noise floor?

Internal ‘inertio-gravity’ wave frequency () band:

f < < N f vert. Cor. Par.; N buoy. freq.

min < f, N < max incl. fh hor. Cor. Par.

0 < < 2 for N = 0

Bay of Biscay ~45N

Yearlong data : Ek- and polarization spectra Special band f-S2 (Levine 2002)=2:

a change in baseline slope higher harmonics dominate

-1 slope: intermittency?

CR: 1 = circular; 0 =rectilinearGonella (1972)

Algerian Basin ~38N

change in baseline slope: caused by ‘background’, ‘buoyancy

subrange’?

IWB-boundaries: inertial shear (e.g. Pinkel JPO2008)

Canary Basin: ~30N

Ek

S

Inertial shear due to short scales?

sub-inertial shear

Latitude dependence inertial shear (Hibiya et al. 2002)

North-Atlantic Ocean: Inertial shear dominance ~30NPSI/SR but additional process?

Sub-and super-f distribution

Irminger Sea: ~59N Sub-f down; Super-f upSmearing due to small-scale N-steps?

down

up

Non-traditional IGW-bounds min < f; max > N N ~ f

Small-scale stratification layers z = O(1 m)

U(f)

U(D2)

N/f

Large-scale stratification layers z = O(100 m)

Algerian Basin: ~38N

Newly formed water mass 2006

1997

Change in inertial polarization/NGyroscopic gravity waves?

Nonzero w(f) Discrete stratification?S vs N

g

1

2

1<2

fhf

Slantwise stability

Directly observed w-spectra: the importance of N

(Pinkel 1981)

wADCP

N-distribution z=1m

Great Meteor Seamnt: 30N Coupling of w(N) and S(f)?

eADCP

Plankton motions: diurnal + hh

w

S

Yearlong open ocean w-spectra: the importance of N

130 m coherent wT

w=-T/t/(dT/dz)

N-distribution

Madeira Basin: ~32N Relation w(N) and steps: filling continuum?

QuestionsQuestions??

Layer dynamics: Internal waves in the Canary Basin (50 days out of 530)

(Louis Gostiaux/Martin Laan)

Open ocean coherence: importance of 2N

Madeira Basin: ~32N Coherence: IGW 0-phase diff.2N: 180-phase diff shear driven?

z(m)

Yearlong open ocean NIOZ3 T-spectra:

Madeira Basin: ~32N -1 slope Temperature spectra