Search Results

You are looking at 1 - 10 of 79 items for :

  • Frontogenesis/frontolysis x
  • Journal of Physical Oceanography x
  • Refine by Access: All Content x
Clear All
Shun Ohishi
,
Tomoki Tozuka
, and
Meghan F. Cronin

et al. 2008 ; Ogawa et al. 2012 ). Although the importance of SST fronts associated with western boundary currents and their extensions has been recognized, past studies did not investigate reinforcement and relaxation processes for the SST fronts, that is, frontogenesis and frontolysis, in a quantitative manner. Recently, using observational datasets and outputs from a high-resolution coupled general circulation model (CGCM), Tozuka and Cronin (2014) and Ohishi et al. (2016) quantitatively

Full access
Lia Siegelman

equation of the evolution of a buoyancy gradient is given by (5) 1 2 d | ∇ b | 2 d t = F s + ∇ w ⋅ ∇ b , with w being the vertical velocity field ( Hoskins 1982 ). A positive F s indicates the presence of frontogenesis, and a negative F s indicates the presence of frontolysis (i.e., frontal destruction). The exact location of the submesoscale fronts is apparent in the buoyancy anomaly field (blue curve in Fig. 13 ), which exhibits a sharp jump down to 299 m in both fronts. The fronts are

Open access
Leif Thomas
and
Raffaele Ferrari

the vertical vorticity. Equation (6) highlights the various phenomena that can result in restratification (or destratification) of the ocean: frontogenesis or frontolysis (FRONT), advection of PV (ADV), friction (FRIC), and diabatic processes (DIA). If the vertical levels z t and z b do not intersect surface and benthic boundary layers, then advection of PV through the bounding surfaces dominates over the other three terms: diabatic and frictional effects are weak away from boundaries, while

Full access
James C. McWilliams
,
Jonathan Gula
, and
M. Jeroen Molemaker

velocity at the tropopause, except for the last one ( Keyser and Shapiro 1986 ). The particular characteristic of a narrower trough implies horizontally confluent flow along the uptrough sector and diffluent flow downtrough. From the classical perspective of strain-induced frontogenesis ( Hoskins and Bretherton 1972 ), we can therefore expect frontogenesis and frontolysis, respectively, in these sectors. The other shape characteristics have not been assessed for their SCFT implications. We now define

Full access
Zhiyou Jing
,
Baylor Fox-Kemper
,
Haijin Cao
,
Ruixi Zheng
, and
Yan Du

buoyancy flux [ EBF = ⁡ ( τ w   ×   z ^ / f ρ 0 ) ⋅ ∇ h b | z = 0 ] ( Thomas et al. 2013 ). In the upper ocean where eddies are most active, elongated surface density fronts and filaments are sharpened by the strain from larger-scale flows that enhance lateral buoyancy gradients via strain-induced frontogenesis (e.g., McWilliams et al. 2009a ; Gula et al. 2014 ). The horizontal strain rate arising from frontogenesis/frontolysis is given by the following expression: (5) St = ⁡ ( u x − υ y ) 2 + ⁡ ( υ

Full access
Yang Yang
,
James C. McWilliams
,
X. San Liang
,
Hong Zhang
,
Robert H. Weisberg
,
Yonggang Liu
, and
Dimitris Menemenlis

comparison, the ratio of the color scales among the three plots are chosen as the same as the bottom panels of Fig. 3 . Region 3 has the strongest buoyancy conversion among the three subdomains and displays a clear winter maximum which corresponds to the seasonal phase of the MLD and F s ( Figs. 3j and 5c ). This suggests that both mixed layer instability and strain-induced frontogenesis are at work in this region. It is interesting to note that intense frontolysis occurs beneath the mixed layer

Full access
Leif N. Thomas
and
Terrence M. Joyce

direct circulation was observed at the Antarctic Polar Front ( Naveira Garabato et al. 2001 ) and the Azores Front ( Rudnick 1996 ), which points to the importance of baroclinic instability in driving frontolysis, restratification, and net subduction at ocean fronts. The thermohaline intrusion descended along the 26.3 kg m −3 isopycnal surface, which is in the seasonal pycnocline that capped the EDW at this early stage in the winter season. The pycnostad to the south of the Gulf Stream’s center was

Full access
James C. McWilliams
,
M. J. Molemaker
, and
E. I. Olafsdottir

fluctuations extract energy mostly from the 2D frontal flow, increasingly with t 0 . This indicates that fluctuations play some role in retarding frontogenesis (often referred to as frontolysis) at least in an integral sense. Here we refine that characterization by examining the frontogenetic tendency balance ( Giordani and Caniaux 2001 ) derived from the alongfront-averaged buoyancy conservation equation including the nonlinear eddy flux. For simplicity we write it in untransformed coordinates (also used

Full access
Roy Barkan
,
M. Jeroen Molemaker
,
Kaushik Srinivasan
,
James C. McWilliams
, and
Eric A. D’Asaro

contribution by Ω k j , typically referred to as the (horizontal) rotation tensor, cancels out. Because F hor b in Eq. (A3) is written as a tensor dot product, it is in coordinate invariant form. Furthermore, Eq. (A3) illustrates that the components of the horizontal strain-rate tensor determine the rate of frontogenesis of frontolysis. The nondimensional S k j and b , k b , j subject to the scaling in Eq. (7) are (A4) S k j = [ Ro u x 1 2 ⁡ ( υ x + ε Ro u y ) 1 2 ⁡ ( υ x + ε Ro u y ) ε υ y

Full access
Tao Wang
,
Roy Barkan
,
James C. McWilliams
, and
M. Jeroen Molemaker

tendency is positive in most parts of F1 ( Fig. 5c ), indicating an increase in horizontal velocity gradient at the moment. As shown in Figs. 5d–f , the horizontal advective tendency dominates in frontogenesis, and the vertical mixing term dominates in frontolysis. The vertical advection term is frontolytic, but its absolute value is much smaller than vertical mixing term ( Fig. 5e ). Fig . 5. Instantaneous horizontal patterns of (a) density (colors) and horizontal velocities (arrows), (b) frontal

Full access