scholarly journals Nonseasonal Variations in Near-Inertial Kinetic Energy Observed Far Below the Surface Mixed Layer in the Southwestern East Sea (Japan Sea)

2021 ◽  
Vol 10 (1) ◽  
pp. 9
Author(s):  
Suyun Noh ◽  
SungHyun Nam
Keyword(s):  
Kinetic Energy ◽  
Mixed Layer ◽  
Surface Wind ◽  
Japan Sea ◽  
Relative Vorticity ◽  
East Sea ◽  
Total Strain ◽  
Surface Mixed Layer ◽  
Capture Process ◽  
Long Time

Near-inertial internal waves (NIWs) generated by surface wind forcing are intermittently enhanced below and within the surface mixed layer. The NIW kinetic energy below the surface mixed layer varies over intraseasonal, interannual, and decadal timescales; however, these variations remain unexplored, due to a lack of long-term, in situ observations. We present statistical results on the nonseasonal variability of the NIW kinetic energy 400 m below the surface mixed layer in the southwestern East Sea, using moored current measurements from 21 years. We used long time series of the near-inertial band (0.85–1.15 f) kinetic energy to define nine periods of relatively high (period high) and seven periods of relatively low (period low) NIW kinetic energy. The NIW kinetic energy average at period high was about 24 times higher than that at period low and those in specific years (2003, 2012–2013, 2016, and 2020) and decade (2010s) were significantly higher than those in other years and decade (2000s). Composite analysis revealed that negative relative vorticity and strong total strain significantly enhance NIW kinetic energy at 400 m. The relative vorticity was negative (total strain was positively enhanced) during seven (six) out of nine events of period high. NIW trapping in a region of negative relative vorticity and the wave capture process induce nonseasonal variations in NIW kinetic energy below the surface mixed layer. Our study reveals that, over intraseasonal, interannual, and decadal timescales, mesoscale flow fields significantly influence NIWs.

Mixed Layer Heat Balance on Intraseasonal Time Scales in the Northwestern Tropical Atlantic Ocean*

2005 ◽  
Vol 18 (20) ◽  
pp. 4168-4184 ◽  
Author(s):  
Gregory R. Foltz ◽  
Michael J. McPhaden
Keyword(s):  
Time Scales ◽  
Mixed Layer ◽  
Heat Balance ◽  
Dominant Role ◽  
Surface Wind ◽  
Local Heat ◽  
Warm Pool ◽  
Surface Mixed Layer ◽  
Tropical Atlantic ◽  
Equatorial Atlantic

Abstract Recent observations have shown evidence of intraseasonal oscillations (with periods of approximately 1–2 months) in the northern and southern tropical Atlantic trade winds. In this paper, the oceanic response to the observed intraseasonal wind variability is addressed through an analysis of the surface mixed layer heat balance, focusing on three locations in the northwestern tropical Atlantic where in situ measurements from moored buoys are available (14.5°N, 51°W; 15°N, 38°W; and 18°N, 34°W). It is found that local heat storage at all three locations is balanced primarily by wind-induced latent heat loss, which is the same mechanism that is believed to play a dominant role on interannual and decadal time scales in the region. It is also found that the intraseasonal wind speed oscillations are linked to changes in surface wind convergence and convection over the western equatorial Atlantic warm pool. These atmospheric circulation anomalies and wind-induced SST anomalies potentially feed back on one another to affect longer time-scale variability in the region.

scholarly journals Cold-Water Events and Dissipation in the Mixed Layer of a Lake

2006 ◽  
Vol 36 (10) ◽  
pp. 1928-1939 ◽  
Author(s):  
B. Ozen ◽  
S. A. Thorpe ◽  
U. Lemmin ◽  
T. R. Osborn
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Mixed Layer ◽  
Large Scale ◽  
Cold Water ◽  
Velocity Shear ◽  
Surface Mixed Layer ◽  
Near Surface ◽  
Law Of The Wall ◽  
Upward Direction

Abstract Measurements of temperature, velocity, and microscale velocity shear were made from the research submarine F. A. Forel in the near-surface mixed layer of Lake Geneva under conditions of moderate winds of 6–8 m s−1 and of net heating at the water surface. The submarine carried arrays of thermistors and a turbulence package, including airfoil shear probes. The rate of dissipation of turbulent kinetic energy per unit mass, estimated from the variance of the shear, is found to be lognormally distributed and to vary with depth roughly in accordance with the law of the wall at the measurement depths, 15–20 times the significant wave height. Measurements revealed large-scale structures, coherent over the 2.38-m vertical extent sampled by a vertical array of thermistors, consisting of filaments tilted in the wind direction. They are typically about 1.5 m wide, decreasing in width in the upward direction, and are horizontally separated by about 25 m in the downwind direction. Originating in the upper thermocline, they are characterized in the mixed layer by their relatively low temperature and low rates of dissipation of turbulent kinetic energy and by an upward vertical velocity of a few centimeters per second.

scholarly journals Parsing the Kinetic Energy Budget of the Ocean Surface Mixed Layer

2022 ◽  
Author(s):  
Seth F. Zippel ◽  
J. Thomas Farrar ◽  
Christopher J. Zappa ◽  
Albert J. Plueddemann
Keyword(s):  
Kinetic Energy ◽  
Mixed Layer ◽  
Energy Budget ◽  
Ocean Surface ◽  
Surface Mixed Layer ◽  
Kinetic Energy Budget ◽  
Ocean Surface Mixed Layer

scholarly journals Impact of an anticyclonic eddy on the summer nutrient and chlorophyll a distributions in the Ulleung Basin, East Sea (Japan Sea)

2011 ◽  
Vol 69 (1) ◽  
pp. 23-29 ◽  
Author(s):  
Dongseon Kim ◽  
Eun Jin Yang ◽  
Kyung Hee Kim ◽  
Chang-Woong Shin ◽  
Jisoo Park ◽  
...  
Keyword(s):  
Water Column ◽  
Chlorophyll A ◽  
Surface Waters ◽  
Japan Sea ◽  
Anticyclonic Eddy ◽  
East Sea ◽  
Ulleung Basin ◽  
Surface Mixed Layer ◽  
High Concentration ◽  
Chl A

Abstract Kim, D., Yang, E. J., Kim, K. H., Shin, C-W., Park, J., Yoo, S., and Hyun, J-H. 2012. Impact of an anticyclonic eddy on the summer nutrient and chlorophyll a distributions in the Ulleung Basin, East Sea (Japan Sea). – ICES Journal of Marine Science, 69: 23–29. The impact of the anticyclonic Ulleung Warm Eddy (UWE) on the vertical distributions of nutrient and chlorophyll a (Chl a) concentrations in the Ulleung Basin (UB) was investigated during the contrasting summers of 2005 and 2007. The physical structure of the water column was characterized by an intrathermocline eddy (ITE) in 2005, whereas the UWE remained distant from the sampling transect in 2007. Water column structures appeared to be highly stratified, and nutrients in the surface waters were totally depleted at all stations. In 2005, an exceptionally high concentration of Chl a (5.5 mg m−3) was measured below the surface mixed layer in the eddy core (station D3), and values of ∼2.5 mg m–3 were observed at the eddy edge (stations D2 and D4). Formation of an ITE efficiently mixed surface and deep-ocean waters, the latter supplying sufficient nutrients to generate an extremely high concentration of Chl a at the base of the subsurface layer. Overall, the results indicated that the anticyclonic UWE plays a key ecological role in supporting substantial phytoplankton biomass in the nutrient-depleted surface waters in summer and maintaining high benthic mineralization in the deep-sea sediments of the UB.

scholarly journals A New Look at Richardson Number Mixing Schemes for Equatorial Ocean Modeling

2009 ◽  
Vol 39 (10) ◽  
pp. 2652-2664 ◽  
Author(s):  
Edward D. Zaron ◽  
James N. Moum
Keyword(s):  
Heat Flux ◽  
Kinetic Energy ◽  
Mixed Layer ◽  
Richardson Number ◽  
Large Scale ◽  
Ocean Modeling ◽  
Depth Range ◽  
Surface Mixed Layer ◽  
Flux Divergence ◽  
Equatorial Undercurrent

Abstract A reexamination of turbulence dissipation measurements from the equatorial Pacific shows that the turbulence diffusivities are not a simple function of the gradient Richardson number. A widely used mixing scheme, the K-profile parameterization, overpredicts the turbulent vertical heat flux by roughly a factor of 4 in the stably stratified region between the surface mixed layer and the Equatorial Undercurrent (EUC). Additionally, the heat flux divergence is of the incorrect sign in the upper 80 m. An alternative class of parameterizations is examined that expresses the mixing coefficients in terms of the large-scale kinetic energy, shear, and Richardson number. These representations collapse the turbulence diffusivities above and below the Equatorial Undercurrent, and a tuned version is able to reproduce the vertical turbulence heat flux within the 50–180-m depth range. Kinetic energy is not Galilean invariant, so the collapse of the data with the new parameterization suggests that oceanic turbulence responds to boundary forcing at depths well below the surface mixed layer.

scholarly journals Spatial and Seasonal Variations of Submesoscale Eddies in the Eastern Tropical Pacific Ocean

2018 ◽  
Vol 48 (1) ◽  
pp. 101-116 ◽  
Author(s):  
Shengpeng Wang ◽  
Zhao Jing ◽  
Hailong Liu ◽  
Lixin Wu
Keyword(s):  
Pacific Ocean ◽  
Kinetic Energy ◽  
Mixed Layer ◽  
Seasonal Variations ◽  
Seasonal Cycle ◽  
Tropical Pacific ◽  
Surface Mixed Layer ◽  
Barotropic Instability ◽  
Tropical Pacific Ocean ◽  
Eastern Tropical Pacific

AbstractThe spatial and seasonal variations of submesoscale eddy activities in the eastern tropical Pacific Ocean (2°–12°N, 95°–165°W) are investigated based on a 1/10° ocean general circulation model (OGCM). In the studied region, it is found that motions shorter than 500 km are subject to submesoscale dynamics with an O(1) Rossby number and Richardson number and a −2 spectral slope for kinetic energy, suggesting that submesoscale eddies there can be well resolved by the model. Enhanced submesoscale eddy kinetic energy (SMKE) is found in the surface mixed layer centered at 5°N. A complete SMKE budget analysis suggests that the submesoscale eddies in the surface mixed layer are generated mainly by the barotropic instability and secondarily by the baroclinic instability. The nonlinear interactions lead to a significant forward energy cascade in the submesoscale range and play an important role in balancing the energy budget. As a response to the change of energy input through barotropic instability, the SMKE exhibits a pronounced seasonal cycle with the largest and smallest values occurring in boreal autumn and spring. Furthermore, the strong seasonal cycle plays an important role in modulating the seasonality of mixed layer depth (MLD). In particular, the restratification induced by the strong submesoscale eddies between July and October makes important contribution to the shoaling of MLD in this season.

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