SearchWorks Catalog Stanford Libraries. Water boundaries : demystifying land boundaries adjacent to tidal or navigable waters. Responsibility Bruce S. Imprint New York : Wiley, c Physical description lvii, p.
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Series Wiley series in surveying and boundary control. Online Available online. Full view. Law Library Crown. F59 Unknown. More options. Find it at other libraries via WorldCat Limited preview. Bibliography Includes bibliographical references and index. Contents Preface. Table of Authorities. The Basics of Land Title. What is the Choice-of-Law? Property Boundary Determination in Estuarine Areas. The overturning circulation of the global ocean is regulated by deep-ocean mixing, which transforms cold waters sinking at high latitudes into warmer, shallower waters.
The effectiveness of mixing in driving this transformation is jointly set by the intensity of turbulence near topography and the rate at which well-mixed boundary waters are exchanged with the stratified ocean interior. We use innovative observations of a branch of the overturning circulation in the Southern Ocean to identify a previously undocumented mixing mechanism, by which deep-ocean waters are rapidly laundered through intensified near-boundary turbulence and boundary—interior exchange.
As the conditions triggering this mechanism are common to other branches of the overturning circulation, our findings highlight a requirement for its representation in models of the overturning. The overturning circulation of the global ocean is critically shaped by deep-ocean mixing, which transforms cold waters sinking at high latitudes into warmer, shallower waters.
The effectiveness of mixing in driving this transformation is jointly set by two factors: the intensity of turbulence near topography and the rate at which well-mixed boundary waters are exchanged with the stratified ocean interior. Here, we use innovative observations of a major branch of the overturning circulation—an abyssal boundary current in the Southern Ocean—to identify a previously undocumented mixing mechanism, by which deep-ocean waters are efficiently laundered through intensified near-boundary turbulence and boundary—interior exchange.
The linchpin of the mechanism is the generation of submesoscale dynamical instabilities by the flow of deep-ocean waters along a steep topographic boundary. As the conditions conducive to this mode of mixing are common to many abyssal boundary currents, our findings highlight an imperative for its representation in models of oceanic overturning.
As cold abyssal waters flow above a rough seafloor, bottom-intensified, small-scale turbulence induces mixing with warmer overlying layers, leading to a net warming and upwelling of abyssal waters along topography 3 , 4. To address this important gap, we conducted a set of systematic measurements of the hydrographic, velocity, and shear microstructure properties of a major abyssal boundary current in the Southern Ocean. Abyssal boundary currents convey newly ventilated waters sinking to great depth at high latitudes away from their sources and underpin the deepest limb of the overturning circulation 3 , 4.
Water Boundaries : Bruce S. Flushman :
In the boundary current targeted here, Antarctic Bottom Water formed in the Weddell Sea outflows the region by skirting the topographic barrier of the South Scotia Ridge and negotiating the narrow, 3,m-deep Orkney Passage 15 , 16 Fig. The observations were obtained in March 20—May 1, from RRS James Clark Ross under the auspices of the UK—US Dynamics of the Orkney Passage Outflow DynOPO project 17 , and consisted of two core elements: a series of fifteen 6- to km-long vessel-based sections of profile measurements crossing the boundary current at an unusually high horizontal resolution Fig.
Further details of the dataset are given in Materials and Methods.
Along-stream evolution of the abyssal boundary current in the Orkney Passage region. The observational domain is shown by the red outline in the Inset large-area map, with major Antarctic Bottom Water AABW pathways indicated in yellow 15 , Sections of measurements are marked by blue coarse-resolution, A1—A7 and green fine-resolution, B1—B8 lines in the main map.
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Observations of horizontal velocity averaged vertically over the AABW layer [defined by neutral density in excess of Bathymetry is denoted by gray shading in both maps. Outer panels show along-slope velocity shading; positive values indicate flow that is directed equatorward, i. Yellow ticks at the base of each Inset mark the locations of measurement profiles. Antarctic Bottom Water, denser than Second, the boundary flow broadens considerably as it traverses the passage.
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This broadening is manifested in an along-stream flattening of density surfaces over the topographic slope cf. Third, the boundary current experiences a pronounced lightening as it circulates through the passage, evident in the gradual waning of waters denser than The deepening, broadening, and lightening of the boundary flow suggest that the current undergoes substantial drag, lateral exchange, and turbulent mixing in crossing the passage, respectively. This raises the question as to which mechanism may trigger a concurrent intensification of these seemingly distinct phenomena.
The governing mechanism is documented by the observations along the high-resolution sections crossing the onshore edge of the boundary current, illustrated here with Fig. As the boundary current approaches the main sill of the Orkney Passage, it flows along the topographic slope with a peak speed of 0. The high-velocity core of the boundary current is embedded within a cross-slope overturning circulation entailing a downslope near-bottom flow in excess of 0.
The overturning acts to tilt density surfaces near the slope and thereby counteracts, through thermal wind, the intensification of the boundary current on its approach to the main sill Fig. Fine-resolution transect across the abyssal boundary current near the Orkney Passage sill. A Along-slope velocity color, with flow direction indicated above the color bar and neutral density in kilograms per cubic meter, black contours; only contours within Antarctic Bottom Water are shown for section B3 Fig. The mean positions of measurement profiles are marked by yellow tick marks on the lower axis.
B Cross-slope velocity color and neutral density black contours. D Potential vorticity color and neutral density black contours. As the cross-slope circulation extends 2—4 km horizontally away from the topography, it promotes rapid lateral exchange of near-boundary and interior waters. The downslope and on-slope limbs of the overturning are consistently characterized by elevated small-scale turbulence Fig.
S1 A exceeding oceanic background values by typically one to three orders of magnitude. The intensification of turbulence within the on-slope flow is, in turn, associated with a series of patches of enhanced vertical shear, with respective cross-slope and vertical scales of 1 km and m.
To elucidate these dynamics, the susceptibility of the boundary flow to submesoscale overturning instabilities is assessed by examining the distribution of potential vorticity q along transect B3 Fig. The procedures for this and subsequent calculations are described in Materials and Methods. A variety of overturning instabilities may develop in a geophysical fluid when q takes the opposite sign to the planetary vorticity 18 , 19 , which is negative in the Southern Hemisphere.
These instabilities induce an overturning circulation that extracts energy from the background flow and expends it in the production of small-scale turbulence, mixing the fluid toward a state of marginal stability. The fulfillment of the instability criterion in this near-boundary zone indicates that the cross-slope overturning Fig.
The nature of the instability experienced by the boundary current is assessed by quantifying the relative importance of the three above factors contributing to the instability criterion in the B3 transect data Materials and Methods. The boundary current is revealed to be primarily subject to centrifugal and symmetric instabilities Fig.
Energy supply linked to gravitational instability is generally modest. This basic consistency between sources and sinks of turbulent kinetic energy substantiates the involvement of the cross-slope overturning in generating the elevated small-scale turbulence observed within the boundary current Fig. While our preceding characterization of the mechanism of boundary current instability is founded on a single high-resolution transect, its generality and underpinning of major changes along the entire stretch of the current spanned by our observations may be illustrated in two ways.
First, a systematic reversal in the sign of q near topography is common to all high-resolution sections, as is the correspondence of that reversal with conditions favorable to the onset of centrifugal and symmetric instabilities and with elevated turbulence SI Appendix , Fig. These associations occur both in areas of boundary current acceleration along a steepening topographic slope with converging isobaths e.
https://hindfelquetimbsen.cf These reveal a widespread downslope flow of relatively light waters at a rate of 0. Generation of the vortex may implicate the tilting of the onshore edge of the boundary current by the cross-slope circulation SI Appendix , Supplementary Text , a mechanism analogous to that forming tornadoes in the atmosphere 24 and intrathermocline eddies in upper-ocean fronts 25 , These feature a colocation of the most intense rates of downslope flow and dissipation around the anticyclonic vortex, and thereby reaffirm the association of cross-slope overturning with small-scale turbulence along the boundary current.
ALR survey of the abyssal boundary current at the Orkney Passage sill. The approximate center of the anticyclonic vortex downstream of the sill is indicated by a yellow star. In both panels, bathymetry is denoted by gray shading, and transects B3 and B4 are indicated by red lines. In conclusion, our targeted measurements of the abyssal boundary current conveying Antarctic Bottom Water through the Orkney Passage show that centrifugal and symmetric instabilities above the topographic slope underpin the intensified drag, lateral exchange, and turbulent mixing experienced by the boundary flow in navigating the passage.
A high-resolution numerical model of the region 27 , which successfully reproduces all of the basic dynamical features of the observations SI Appendix , Supplementary Text and Figs. The stress induces a flow to the right of the current that advects relatively light water down the slope, tilting isopycnals toward the vertical and compressing them horizontally Fig. This flow leads to a progressive reduction of vertical stratification and enhancement of lateral stratification and shear to the point that these lateral gradients become large enough for the flow to develop centrifugal and symmetric instabilities.
The instabilities promote a cross-slope overturning circulation that conveys well-mixed near-boundary waters away from the slope and replenishes the near-boundary zone with more strongly stratified offshore waters. Schematic of the mechanism of mixing and exchange in an abyssal boundary current. The direction of the boundary current is indicated by the cross and the direction of the cross-slope overturning is denoted by solid black arrows. Surfaces of constant density are shown as interfaces between blue-shaded layers.
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