Spectral slopes and peaks: moored observations of internal waves in the ocean Hans van Haren
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Transcript of 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