The catastrophe structure of thermohaline convection in a two-dimensional fluid model and a comparison with low-order box models

Thual, Olivier; McWilliams, James C.

doi:10.1080/03091929208228085

Cited by 112 publications

(139 citation statements)

References 12 publications

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“…Studies with simple box ocean models [39,49] have indicated that several equilibria may be stable under the same forcing conditions. Similar results were obtained for two-dimensional ocean models [43,31,8] and zonally integrated models [29,53]. In three-dimensional single hemispheric sector models, two different equilibrium flow patterns are found [46] when the strength of the freshwater flux forcing is large enough.…”

Section: Introductionsupporting

confidence: 72%

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A Fully Implicit Model of the Three-Dimensional Thermohaline Ocean Circulation

Dijkstra¹,

Öksüzoǧlu²,

Wubs

et al. 2001

Journal of Computational Physics

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Section: Introductionsupporting

confidence: 72%

“…The structure of the bifurcation diagrams, with two saddle node bifurcations introducing a region of multiple equilibria is in correspondence with those from box-models [39,43]. The structure of the multiple equilibria is found for all the resolutions in Fig.…”

Section: Basic Bifurcation Diagramsmentioning

confidence: 53%

A Fully Implicit Model of the Three-Dimensional Thermohaline Ocean Circulation

Dijkstra¹,

Öksüzoǧlu²,

Wubs

et al. 2001

Journal of Computational Physics

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“…Two different domain configurations are studied: the first one considers a model with equatorially symmetric surface buoyancy forcing. This model, which will be denoted as 'global', has been studied by several authors in as many parameter settings (Cessi and Young 1992;Thual and McWilliams 1992;Ghil 1992, 1995;Dijkstra and Molemaker 1997). The second configuration, called 'Atlantic', applies more specifically to the Atlantic ocean, which we consider bounded by the 30 • S parallel.…”

Section: The Model a Domain And Configurationmentioning

confidence: 99%

Impact of Interbasin Exchange on the Atlantic Overturning Circulation

et al. 1999

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The thermohaline exchange between the Atlantic and the Southern Ocean is analyzed, using a data set based on WOCE hydrographic data. It is shown that the salt and heat transports brought about by the South Atlantic subtropical gyre play an essential role in the Atlantic heat and salt budgets. It is found that on average the exported North Atlantic Deep Water (NADW) is fresher than the return flows (basically composed of thermocline and intermediate water), indicating that the overturning circulation (OC) exports freshwater from the Atlantic.The sensitivity of the OC to interbasin fluxes of heat and salt is studied in a 2D model, representing the Atlantic between 60 • N and 30 • S. The model is forced by mixed boundary conditions at the surface, and by realistic fluxes of heat and salt at its 30 • S boundary. The model circulation turns out to be very sensitive to net buoyancy fluxes through the surface. Both net surface cooling and net surface saltening are sources of potential energy and impact positively on the circulation strength. The vertical distributions of the lateral fluxes tend to stabilize the stratification, and, as they extract potential energy from the system, tend to weaken the flow. These results imply that a change in the composition of the NADW return transports, whether by a change in the ratio thermocline/intermediate water, or by a change in their thermohaline characteristics, might influence the Atlantic OC considerably.It is also shown that the circulation is much more sensitive to changes in the shape of the lateral buoyancy flux than to changes in the shape of the surface buoyancy flux, as the latter does not explicitly impact on the potential energy of the system. It is concluded that interocean fluxes of heat and salt are important for the strength and operation of the Atlantic thermohaline circulation, and should be correctly represented in models that are used for climate sensitivity studies.

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“…Several authors have expanded Stommel's box-model to allow for more features of THC (Rooth, 1982;Welander, 1986;Thual and Mcwilliams, 1992;Rahmstorf, 1996). We will here construct a box-model which allows for THC associated with subsequent buoyancy loss and buoyancy gain.…”

Section: Introductionmentioning

confidence: 99%

How northern freshwater input can stabilise thermohaline circulation

Lambert

Eldevik

Haugan

2016

Tellus A: Dynamic Meteorology and Oceanography

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A B S T R A C TThe North Atlantic thermohaline circulation (THC) carries heat and salt towards the Arctic. This circulation is partly sustained by buoyancy loss and is generally believed to be inhibited by northern freshwater input as indicated by the 'box-model ' of Stommel (1961). The inferred freshwater-sensitivity of the THC, however, varies considerably between studies, both quantitatively and qualitatively. The northernmost branch of the Atlantic THC, which forms a double estuarine circulation in the Arctic Mediterranean, is one example where both buoyancy loss and buoyancy gain facilitate circulation. We have built on Stommel's original concept to examine the freshwater-sensitivity of a double estuarine circulation. The net inflow into the double estuary is found to be more sensitive to a change in the distribution of freshwater than to a change in the total freshwater input. A double estuarine circulation is more stable than a single overturning, requiring a larger amount and more localised freshwater input into regions of buoyancy loss to induce a thermohaline 'collapse'. For the Arctic Mediterranean, these findings imply that the Atlantic inflow may be relatively insensitive to increased freshwater input. Complementing Stommel's thermal and haline flow regimes, the double estuarine circulation allows for a third: the throughflow regime. In this regime, a THC with warm poleward surface flow can be sustained without production of dense water; a decrease in high-latitude dense water formation does therefore not necessarily affect regional surface conditions as strongly as generally thought.

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The catastrophe structure of thermohaline convection in a two-dimensional fluid model and a comparison with low-order box models

Cited by 112 publications

References 12 publications

A Fully Implicit Model of the Three-Dimensional Thermohaline Ocean Circulation

A Fully Implicit Model of the Three-Dimensional Thermohaline Ocean Circulation

Impact of Interbasin Exchange on the Atlantic Overturning Circulation

How northern freshwater input can stabilise thermohaline circulation

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