spectral slopes and peaks: moored observations of internal waves in the ocean hans van haren

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