scholarly journals Mechanisms of wind‐induced low‐frequency ambient sea noise in the deep ocean

1980 ◽  
Vol 67 (S1) ◽  
pp. S95-S95
Author(s):  
N. Yen ◽  
A. J. Perrone
Keyword(s):  
Low Frequency ◽  
Deep Ocean

scholarly journals Climate Process Team on Internal Wave–Driven Ocean Mixing

2017 ◽  
Vol 98 (11) ◽  
pp. 2429-2454 ◽  
Author(s):  
Jennifer A. MacKinnon ◽  
Zhongxiang Zhao ◽  
Caitlin B. Whalen ◽  
Amy F. Waterhouse ◽  
David S. Trossman ◽  
...  
Keyword(s):  
Internal Wave ◽  
Turbulent Mixing ◽  
Low Frequency ◽  
Internal Tide ◽  
Deep Ocean ◽  
Global Ocean ◽  
Primary Role ◽  
Inverse Models ◽  
Lee Waves ◽  
Mixing Rates

Abstract Diapycnal mixing plays a primary role in the thermodynamic balance of the ocean and, consequently, in oceanic heat and carbon uptake and storage. Though observed mixing rates are on average consistent with values required by inverse models, recent attention has focused on the dramatic spatial variability, spanning several orders of magnitude, of mixing rates in both the upper and deep ocean. Away from ocean boundaries, the spatiotemporal patterns of mixing are largely driven by the geography of generation, propagation, and dissipation of internal waves, which supply much of the power for turbulent mixing. Over the last 5 years and under the auspices of U.S. Climate Variability and Predictability Program (CLIVAR), a National Science Foundation (NSF)- and National Oceanic and Atmospheric Administration (NOAA)-supported Climate Process Team has been engaged in developing, implementing, and testing dynamics-based parameterizations for internal wave–driven turbulent mixing in global ocean models. The work has primarily focused on turbulence 1) near sites of internal tide generation, 2) in the upper ocean related to wind-generated near inertial motions, 3) due to internal lee waves generated by low-frequency mesoscale flows over topography, and 4) at ocean margins. Here, we review recent progress, describe the tools developed, and discuss future directions.

Propagation of Low‐Frequency CW Sound Signals in the Deep Ocean

1965 ◽  
Vol 38 (6) ◽  
pp. 1060-1061 ◽  
Author(s):  
Albert N. Guthrie ◽  
John D. Shaffer
Keyword(s):  
Low Frequency ◽  
Deep Ocean

scholarly journals Climate models can correctly simulate the continuum of global-average temperature variability

2019 ◽  
Vol 116 (18) ◽  
pp. 8728-8733 ◽  
Author(s):  
Feng Zhu ◽  
Julien Emile-Geay ◽  
Nicholas P. McKay ◽  
Gregory J. Hakim ◽  
Deborah Khider ◽  
...  
Keyword(s):  
Climate Models ◽  
Initial Conditions ◽  
Low Frequency ◽  
Deep Ocean ◽  
Critical Element ◽  
Average Temperature ◽  
Global Mean Temperature ◽  
Low Frequency Variability ◽  
Climate Forcings ◽  
Global Mean

Climate records exhibit scaling behavior with large exponents, resulting in larger fluctuations at longer timescales. It is unclear whether climate models are capable of simulating these fluctuations, which draws into question their ability to simulate such variability in the coming decades and centuries. Using the latest simulations and data syntheses, we find agreement for spectra derived from observations and models on timescales ranging from interannual to multimillennial. Our results confirm the existence of a scaling break between orbital and annual peaks, occurring around millennial periodicities. That both simple and comprehensive ocean–atmosphere models can reproduce these features suggests that long-range persistence is a consequence of the oceanic integration of both gradual and abrupt climate forcings. This result implies that Holocene low-frequency variability is partly a consequence of the climate system’s integrated memory of orbital forcing. We conclude that climate models appear to contain the essential physics to correctly simulate the spectral continuum of global-mean temperature; however, regional discrepancies remain unresolved. A critical element of successfully simulating suborbital climate variability involves, we hypothesize, initial conditions of the deep ocean state that are consistent with observations of the recent past.

Coherence of low‐frequency acoustic signals in the deep ocean

1974 ◽  
Vol 56 (4) ◽  
pp. 1122-1125 ◽  
Author(s):  
J. D. Shaffer ◽  
R. M. Fitzgerald ◽  
A. N. Guthrie
Keyword(s):  
Low Frequency ◽  
Deep Ocean ◽  
Acoustic Signals

Upslope propagation of low frequency deep ocean signals

2018 ◽  
Vol 144 (3) ◽  
pp. 1733-1733
Author(s):  
Gerald L. D'Spain ◽  
Kenneth Houston ◽  
Robert Tingley ◽  
Terry Nawara ◽  
Daniel Lawrence ◽  
...  
Keyword(s):  
Low Frequency ◽  
Deep Ocean

PROPELLER NOISE FROM A LIGHT AIRCRAFT FOR LOW-FREQUENCY MEASUREMENTS OF THE SPEED OF SOUND IN A MARINE SEDIMENT

2002 ◽  
Vol 10 (04) ◽  
pp. 445-464 ◽  
Author(s):  
MICHAEL J. BUCKINGHAM ◽  
ERIC M. GIDDENS ◽  
FERNANDO SIMONET ◽  
THOMAS R. HAHN
Keyword(s):  
Water Column ◽  
Speed Of Sound ◽  
Low Frequency ◽  
Deep Ocean ◽  
Fine Sand ◽  
P Wave ◽  
Difference Frequency ◽  
S Wave ◽  
Low Frequencies ◽  
La Jolla

The sound from a light aircraft in flight is generated primarily by the propeller, which produces a sequence of harmonics in the frequency band between about 80 Hz and 1 kHz. Such an airborne sound source has potential in underwater acoustics applications, including inversion procedures for determining the wave properties of marine sediments. A series of experiments has recently been performed off the coast of La Jolla, California, in which a light aircraft was flown over a sensor station located in a shallow (approximately 15 m deep) ocean channel. The sound from the aircraft was monitored with a microphone above the sea surface, a vertical array of eight hydrophones in the water column, and two sensors, a hydrophone and a bender intended for detecting shear waves, buried 75 cm deep in the very-fine-sand sediment. The propeller harmonics were detected on all the sensors, although the s-wave was masked by the p-wave on the buried bender. Significant Doppler shifts of the order of 17%, were observed on the microphone as the aircraft approached and departed from the sensor station. Doppler shifting was also evident in the hydrophone data from the water column and the sediment, but to a lesser extent than in the atmosphere. The magnitude of the Doppler shift depends on the local speed of sound in the medium in which the sensor is located. A technique is described in which the Doppler difference frequency between aircraft approach and departure is used to determine the speed of sound at low-frequencies (80 Hz to 1 kHz) in each of the three environments, the atmosphere, the ocean and the sediment. Several experimental results are presented, including the speed of sound in the very fine sand sediment at a nominal frequency of 600 Hz, which was found from the Doppler difference frequency of the seventh propeller harmonic to be 1617 m/s.

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