Topographic Preconditioning of Open-Ocean Deep Convection

Alverson, Keith; Owens, W. Brechner

doi:10.1175/1520-0485(1996)026<2196:tpoood>2.0.co;2

Cited by 48 publications

(49 citation statements)

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“…The e ects of a seamount on the mixed layer in high latitudes have been investigated by Alverson and Owens (1996) and Alverson (1997), who used a similarly con®gured model, and applied buoyancy forcing to study the topographic preconditioning for open ocean convection. In their density-only simulations, the topography introduces a spatial inhomogeneity that will lead to deeper convection above the seamount's upstream¯ank, where the upwelling dense water merges with the surface mixed layer.…”

Section: Theoretical and Modelling Studiesmentioning

confidence: 99%

The effect of flow at Maud Rise on the sea-ice cover numerical experiments

Beckmann¹,

Timmermann²,

Pereira³

et al. 2001

Ocean Dynamics

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The role of seamounts in the formation and evolution of sea ice is investigated in a series of numerical experiments with a coupled sea ice±ocean model. Bottom topography, strati®cation and forcing are con®gured for the Maud Rise region in the Weddell Sea. The speci®c¯ow regime that develops at the seamount as the combined response to steady and tidal forcing consists of free and trapped waves and a vortex cap, which is caused by mean¯ow and tidal¯ow recti®cation. The enhanced variability through tidal motion in particular modi®es the mixed layer above the seamount enough to delay and reduce sea-ice formation throughout the winter. The induced sea-ice anomaly spreads and moves westward and a ects an area of several 100 000 km 2 . Process studies reveal the complex interaction between wind, steady and periodic ocean currents: all three are required in the process of generation of the sea ice and mixed layer anomalies (mainly through tidal¯ow), their detachment from the topography (caused by steady oceanic¯ow) and the westward translation of the sea-ice anomaly (driven by the timemean wind).

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Section: Theoretical and Modelling Studiesmentioning

confidence: 99%

The effect of flow at Maud Rise on the sea-ice cover numerical experiments

Beckmann¹,

Timmermann²,

Pereira³

et al. 2001

Ocean Dynamics

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“…In one sense, it places a lid at the surface, confining the relatively strong stratification just below 200 m. In order to convect deeply during the violent mixing phase, significant cooling is first required to erode the seasonal thermocline and then further mixing takes place rather rapidly to the subsurface. Straneo and Kawase [1999] and Alverson [1995, chapter 4] demonstrated that the vertical structure of the domed isopycnals plays a key role in determining the depth of convective mixing. The magnitude of the vertical density gradient, from the near surface to the subsurface ocean, determines the depth of convection.…”

Section: Resultsmentioning

confidence: 99%

“…A schematic figure from Alverson [1995, Figure 4.4b] provides a simple dynamical explanation for a link between the vertical density gradient and the convective depth. In November 1965 (Figure 7a), the density increases vertically from 27.80 kg/m 3 at 200 m to 27.95 kg/m 3 at 2000 m, whereas in November 1983 it increases from 27.86 kg/m 3 to 27.97 kg/m 3 .…”

Section: Resultsmentioning

confidence: 99%

“…Although the convective process is a complicated system in reality, we approximate the MLD in March simply as a function of the total surface buoyancy flux integrated from November to March and the vertical density profile in November. In order to quantify the relationship, we apply a simple one‐dimensional mixed‐layer model used by Alverson [1995, equation (4.3)] in the following subsection. Our simple model refines the work of Alverson [1995] by including a yearly varying surface buoyancy flux.…”

Section: Resultsmentioning

confidence: 99%

“…They showed the importance of both the buoyancy forcing and the oceanic preconditioning. Alverson [1995, chapter 4] used a simple one‐dimensional mixed‐layer model, with an exponentially increasing vertical density profile representing the domed isopycnals and a constant buoyancy forcing, to examine the doming effect of the oceanic background stratification on the intensity of convection. The results showed that with a constant buoyancy input stratification with more sharply domed isopycnals produces a deeper convective mixing.…”

Section: Introductionmentioning

confidence: 99%

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Convective activity in the Labrador Sea: Preconditioning associated with decadal variability in subsurface ocean stratification

et al. 2003

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[1] The decadal variability of the convective activity in the Labrador Sea is investigated using 43 years of model output from a prognostic coupled ice-ocean model that simulates both the Arctic and the North Atlantic Oceans. The fields of the surface density and the mixed-layer depth indicate that the center of the convective activity is located in western Labrador Sea. The decadal variations of the convective depth are controlled to large extent by the oceanic preconditioning associated with changes in subsurface stratification. The intensity of the convective mixing varies from year to year, depending upon how strong the isopycnal doming is at the preconditioning stage at the center of the convective region. The variations of the subsurface stratification seem to be related to the subsurface temperature changes.

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Replicating the 1970s' Weddell Polynya using a coupled ocean‐sea ice model with reanalysis surface flux fields

Cheon

Lee

Gordon

et al. 2015

Geophysical Research Letters

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The 1970s' Weddell Polynya is simulated in the framework of a coupled ocean‐sea ice model forced by reanalysis surface flux fields. A rapid emergence of strongly negative wind stress curl over the Weddell Sea intensifies the cyclonic Weddell gyre and thus causes the relatively warm and salty Weddell Deep Water (WDW) to upwell, generating an open‐ocean polynya by melting sea ice or hindering its formation. Once the polynya occurs in the austral winter, the underlying water column is destabilized due to the combined effect of the high‐salinity WDW, a massive cooling at the air‐sea interface, and the ensuing brine rejection from newly forming ice, thus inducing open‐ocean deep convection. Further analysis shows that the buildup of a large heat reservoir at depth by the mid‐1970s was a necessary condition to establish the Weddell Polynya of the 1970s.

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Topographic Preconditioning of Open-Ocean Deep Convection

Cited by 48 publications

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The effect of flow at Maud Rise on the sea-ice cover numerical experiments

The effect of flow at Maud Rise on the sea-ice cover numerical experiments

Convective activity in the Labrador Sea: Preconditioning associated with decadal variability in subsurface ocean stratification

Replicating the 1970s' Weddell Polynya using a coupled ocean‐sea ice model with reanalysis surface flux fields

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Topographic Preconditioning of Open-Ocean Deep Convection

Cited by 48 publications

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The effect of flow at Maud Rise on the sea-ice cover  numerical experiments

The effect of flow at Maud Rise on the sea-ice cover  numerical experiments

Convective activity in the Labrador Sea: Preconditioning associated with decadal variability in subsurface ocean stratification

Replicating the 1970s' Weddell Polynya using a coupled ocean‐sea ice model with reanalysis surface flux fields

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The effect of flow at Maud Rise on the sea-ice cover numerical experiments

The effect of flow at Maud Rise on the sea-ice cover numerical experiments