scholarly journals Submesoscale transition from geostrophic flows to internal waves in the northwestern Pacific upper ocean

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Bo Qiu ◽  
Toshiya Nakano ◽  
Shuiming Chen ◽  
Patrice Klein
Keyword(s):  
Internal Waves ◽  
Upper Ocean ◽  
Northwestern Pacific ◽  
Geostrophic Flows

scholarly journals Spatially Broad Observations of Internal Waves in the Upper Ocean at the Hawaiian Ridge

2006 ◽  
Vol 36 (6) ◽  
pp. 1085-1103 ◽  
Author(s):  
Joseph P. Martin ◽  
Daniel L. Rudnick ◽  
Robert Pinkel
Keyword(s):  
Numerical Model ◽  
Energy Density ◽  
Potential Energy ◽  
Internal Waves ◽  
Upper Ocean ◽  
Mean Square ◽  
The South ◽  
South Side ◽  
Topographic Slope ◽  
Hawaiian Ridge

Abstract The density and current structure at the Hawaiian Ridge was observed using SeaSoar and Doppler sonar during a survey extending from Oahu to Brooks Banks. Across- and along-ridge changes in internal wave statistics in the upper ocean within 200 km of the ridge are investigated. Internal waves with trough-to-crest amplitude as large as 60 m and horizontal wavelength of about 50 km are observed repeatedly in across-ridge sections of potential density. Within 150 km of the ridge, kinetic and potential energy density exceed open-ocean values with maxima about 10 times Garrett–Munk levels. In the Kauai Channel (KC), the kinetic energy density is largest along an M2 internal tide ray. The ray originates at the northern edge of the ridge peak at a large across-ridge change in topographic slope and terminates at the ocean surface about 30–40 km south of the ridge peak. Kinetic and potential energy density are larger on the south side of the ridge at KC, the side with larger topographic slope. Energy density is also larger on the south side of the ridge at KC in numerical model results and on the side of steeper topographic slope in analytical model results. Along the ridge, the largest observed values of mean-square shear and mean-square slope of isopycnal depth are collocated with the largest energy density in numerical model results. Mean-square shear and mean-square slope increase with decreasing bottom depth and with increasing M2 barotropic tidal forcing.

Internal waves in JASIN

1983 ◽  
Vol 308 (1503) ◽  
pp. 389-405 ◽  
Keyword(s):  
Internal Waves ◽  
Internal Tide ◽  
Deep Ocean ◽  
Upper Ocean ◽  
Velocity Measurements ◽  
High Frequencies ◽  
Topographic Features ◽  
Rockall Trough ◽  
Moored Current Meters ◽  
The Continuum

The internal wavefield during the Joint Air—Sea Interaction (JASIN) experiment was monitored by moored current meters and moored and towed thermistor chains. The observations were concentrated in the upper ocean near the centre of Rockall Trough, but velocity measurements were also made near topographic features and throughout the water column. Observed spectra are compared with results from the deep ocean, as represented by the Garrett-Munk (GM) model of the spectral continuum, and are generally found to have spectral levels equal to or greater than the GM spectrum. The greatest deviation from the GM spectrum occurs at high frequencies and wavenumbers where the observed spectra often exhibit a spectral shoulder and high vertical coherence. These features, also found in other upper-ocean spectra, are explained by a model composed of three vertically standing modes. The spatial variation of internal wave variance is related to topography: variance is highest near rough topography. The ratio of variance in the semidiurnal tidal band to variance in a band in the continuum is approximately constant. The possibility of a dynamical link between the two frequency bands requires further investigation. The semidiurnal internal tide varies temporally and spatially. Rockall Bank is identified as the source of an energetic beam of tidal oscillations during a one-week period.

Surface forced internal waves and vortices in uniformly stratified and rotating fluids

2000 ◽  
Vol 421 ◽  
pp. 39-81 ◽  
Author(s):  
RUDOLF C. KLOOSTERZIEL
Keyword(s):  
Internal Waves ◽  
Wave Energy ◽  
Early Time ◽  
Initial Energy ◽  
Simple Expression ◽  
Rotating Fluids ◽  
Homogeneous Fluid ◽  
Coriolis Parameter ◽  
Constant Frequency ◽  
Geostrophic Flows

The motion of an initially quiescent, incompressible, stratified and/or rotating uid of semi-infinite extent due to surface forcing is considered. The stratification parameter N and the Coriolis parameter f are constant but arbitrary and all possible combinations are considered, including N = 0 (rotating homogeneous fluid), f = 0 (non-rotating stratified fluid) and the special case N = f. The forcing is suction or pumping at an upper rigid surface and the response consists of geostrophic flows and inertial-internal waves. The response to impulsive point forcings (Green's functions) is contrasted with the response to finite-sized circularly symmetric impulsive forcings. Early-time and large-time behaviour are studied in detail. At early times transient internal waves change the vortices that are created by pumping/suction at the surface. The asymptotically remaining vortices are determined, a simple expression for what fraction of the initial energy is converted into internal waves is derived, as well as wave energy fluxes and the dependence of the flux direction on the value of N/f. The internal wave field is to leading order in time a distinct pulse, and rules for the arrival time of the pulse, its amplitude, its motion along a ray of constant frequency and decay with time, are given for the far field. A simple formula for the total wave energy distribution as a function of frequency is derived for when all waves have propagated away from the forcing.

scholarly journals Typhoon-Triggered Phytoplankton Bloom and Associated Upper-Ocean Conditions in the Northwestern Pacific: Evidence from Satellite Remote Sensing, Argo Profile, and an Ocean Circulation Model

2020 ◽  
Vol 8 (10) ◽  
pp. 788
Author(s):  
Joon-Ho Lee ◽  
Jae-Hong Moon ◽  
Taekyun Kim
Keyword(s):  
Remote Sensing ◽  
Phytoplankton Bloom ◽  
Cyclonic Circulation ◽  
Sea Surface ◽  
Height Anomaly ◽  
Upper Ocean ◽  
Northwestern Pacific ◽  
Surface Cooling ◽  
Chl A ◽  
Ocean Conditions

A long-lasting phytoplankton bloom, characterized by high chlorophyll-a (Chl-a) concentrations in an eddy-like feature, was detected in MODIS satellite imagery of the northwestern Pacific following the passage of Typhoon Krosa in August 2019. Satellite datasets, Argo measurements, and regional ocean models were analyzed to determine the occurrence and abundance of high-Chl-a concentrations and the upper-ocean conditions associated with them before and after the passage of the typhoon. Remote sensing data revealed that the typhoon triggered sharp increases in surface Chl-a concentrations more than five times the pre-typhoon average, which lasted for two weeks. The elevated post-typhoon concentrations coincided with a pre-existing oceanic cyclone that was detected as an altimetry-based sea surface height anomaly. The typhoon looped around the oceanic cyclone and lingered for two days at slow speeds (less than 2 m/s), producing an unusual sea-surface cooling of up to approximately 9 °C in the cyclonic eddy region. Our model successfully captured the typhoon-induced cold-core cyclonic circulation, which corresponded to the region of high Chl-a concentration. Model–data comparisons revealed that the looping motion of the slow-moving typhoon enhanced the pre-existing cyclonic circulation, resulting in strong vertical mixing and upwelling, consequently initiating a phytoplankton bloom due to increased nutrient supply to the euphotic zone.

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