Search Results

You are looking at 1 - 10 of 28,181 items for :

  • Refine by Access: All Content x
Clear All
Hans Burchard
,
Xaver Lange
,
Knut Klingbeil
, and
Parker MacCready

1. Introduction Estuaries can be regarded as mixing zones which dilute saltwater inflowing from the ocean with freshwater from river runoff to produce brackish water flowing back into the ocean ( Fischer 1976 ). To underline this key estuarine function, Wang et al. (2017) used the name mixing machine to characterize estuarine dynamics. Since mixing is such a fundamental property in estuaries, several authors have proposed quantitative measures for it. In an early estuarine model, Hansen

Open access
Alberto Scotti
and
Brian White

1. Introduction Despite its significance for large-scale geophysical flows ( Wunsch and Ferrari 2004 ), we still lack a precise understanding of how mixing in a stratified environment depends on the environmental conditions that drive it [see, e.g., the review by Ivey et al. (2008) and references therein]. If we view mixing as any mechanism that pumps buoyancy against a gravitational potential gradient, we can think of its efficiency as the fraction of the energy consumed by the system that

Full access
Lixin Qu
,
Robert D. Hetland
, and
Dylan Schlichting

1. Introduction Mixing can be defined as the destruction of variance. For microstructure variations in momentum, this is written as ϵ , the rate of turbulent kinetic energy dissipation; for tracers it is written as χ , the rate of tracer microstructure variance destruction. In both cases, the destruction of variance is an irreversible process. Currently, not even very high-resolution numerical ocean models that focus on estuarine and coastal ocean domains are able to resolve

Open access
W. D. Smyth
,
J. R. Carpenter
, and
G. A. Lawrence

of which may lead to turbulence and mixing. These are the Kelvin–Helmholtz (KH) instability, which consists of a stationary train of billows focused at the central plane, and the Holmboe instability, which consists of a pair of oppositely propagating wave trains, focused above and below the central plane, that interfere to form a standing wave–like structure ( Holmboe 1962 ; Smyth et al. 1988 ). In this paper, we examine mixing processes in direct numerical simulations (DNSs) of Holmboe

Full access
W. D. Smyth

available, (1) yields K ρ . One can then take advantage of the fact that different scalar concentrations diffuse at similar rates and therefore use K ρ as an approximation for the diffusivity of heat, salt, CO 2 , or any other scalar. Eventually we hope to be able to calculate values of Γ for all the various processes that mix geophysical fluids. In the interim, we use the provisional value Γ = 0.2. This is an oversimplification, but when checked independently as described below, Γ = 0.2 gives

Open access
Jörn Callies

1. Introduction The return of Antarctic Bottom Water from the abyss back to the surface requires water mass transformation by diapycnal mixing (e.g., Lumpkin and Speer 2007 ; Talley 2013 ). While small-scale turbulence in the bulk of the abyssal ocean is relatively weak, turbulence levels are elevated where tidal or geostrophic flows pass over a rugged seafloor (e.g., Polzin et al. 1997 ; Ledwell et al. 2000 ; St. Laurent et al. 2012 ; Waterhouse et al. 2014 ). Internal waves are excited

Full access
Tongya Liu
,
Yu-Kun Qian
,
Xiaohui Liu
,
Shiqiu Peng
, and
Dake Chen

1. Introduction Mesoscale eddies, primarily induced by the baroclinic instability of the large-scale density field, can stir, mix, and transport oceanic tracers on a global scale, which has a significant effect on the general ocean circulation and the climate-related issues ( Lumpkin and Elipot 2010 ; Abernathey and Marshall 2013 , hereinafter AM13 ; Busecke and Abernathey 2019 ; Liu et al. 2022 ). Proper estimates of the lateral eddy mixing (or diffusivity) would greatly benefit the

Restricted access
Xiaozhou Ruan
and
Raffaele Ferrari

1. Introduction The ocean’s meridional overturning circulation (MOC) regulates Earth’s climate on centennial to millennial time scales through the transport of vast amounts of carbon, heat, and nutrients ( Wunsch 2017 ). While the upper branch of the MOC is thought to be primarily controlled by wind and buoyancy forcing at the ocean surface ( Marshall and Radko 2003 ; Marshall and Speer 2012 ), the lower branch requires interior mixing with overlying waters to balance the surface buoyancy loss

Full access
Yutaka Yoshikawa

1. Introduction Surface winds induce turbulent mixing in the surface layer, while the mixing is moderated by Earth’s rotation. Stabilizing buoyancy fluxes at the ocean surface further weaken wind-induced mixing and shoal the surface mixing layer. The surface mixed layer, through which surface fluxes have been mixed, is a remnant of this surface mixing layer through which surface fluxes are being actively mixed (e.g., Brainerd and Gregg 1995 ; de Boyer Montegut et al. 2004 ). Both the surface

Full access
Cara C. Henning
,
David Archer
, and
Inez Fung

1. Introduction Fluid flow in the upper thermocline occurs largely along isopycnal surfaces, while the rate of cross-isopycnal mixing tends to be small. However, understanding the structure of the thermocline (e.g., Samelson and Vallis 1997 ), the overturning circulation ( Scott and Marotzke 2002 ), the efficiency of potential carbon sequestration experiments ( Mignone et al. 2004 ), and the degree of high-latitude control on the atmospheric p CO 2 concentration ( Archer et al. 2000 ) all

Full access