Decadal warming of the coldest Antarctic Bottom Water flow through the Vema Channel

Zenk, Walter; Morozov, E. G.

doi:10.1029/2007gl030340

Cited by 73 publications

(72 citation statements)

References 16 publications

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“…The simulated dense shelf water cooling matches recent observational trends (Azaneu et al 2013) while preserving the observed warming of the densest waters within the Vema Channel (Zenk and Morozov 2007). No previous work provides a mechanism that may explain the observed cooling of dense shelf waters around Antarctica along with continued far-field warming.…”

Section: Discussionsupporting

confidence: 69%

“…Freshening of both shelf (waters shallower than 1000 m and south of 608S) and AABW water masses (Figs. 7d-f) is consistent with observational evidence (e.g., Zenk and Morozov 2007;Purkey and Johnson 2010;Hellmer et al 2012;Azaneu et al 2013). Freshening of shelf waters is greatest in the warming scenarios because of the dominant role ice removal has in the freshwater flux budget.…”

Section: B Shelf and Deep Ocean Responsesupporting

confidence: 76%

“…Hence, the warmer waters above may constitute a larger portion of AABW entering the Brazil basin as mixing occurs across the relatively shallow Vema Channel (depth of ;4600 m; Zenk and Morozov 2007). This mixing allows warming within the Vema Channel and Brazil basin (as found in observations; Zenk and Morozov 2007) for all simulations, despite the periods of cooling within the Argentine basin (Figs. 7 and 12a).…”

Section: B Shelf and Deep Ocean Responsementioning

confidence: 97%

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Sensitivity of Antarctic Bottom Water to Changes in Surface Buoyancy Fluxes

et al. 2015

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The influence of freshwater and heat flux changes on Antarctic Bottom Water (AABW) properties are investigated within a realistic bathymetry coupled ocean-ice sector model of the Atlantic Ocean. The model simulations are conducted at eddy-permitting resolution where dense shelf water production dominates over open ocean convection in forming AABW. Freshwater and heat flux perturbations are applied independently and have contradictory surface responses, with increased upper-ocean temperature and reduced ice formation under heating and the opposite under increased freshwater fluxes. AABW transport into the abyssal ocean reduces under both flux changes, with the reduction in transport being proportional to the net buoyancy flux anomaly south of 608S.Through inclusion of shelf-sourced AABW, a process absent from most current generation climate models, cooling and freshening of dense source water is facilitated via reduced on-shelf/off-shelf exchange flow. Such cooling is propagated to the abyssal ocean, while compensating warming in the deep ocean under heating introduces a decadal-scale variability of the abyssal water masses. This study emphasizes the fundamental role buoyancy plays in controlling AABW, as well as the importance of the inclusion of shelf-sourced AABW within climate models in order to attain the complete spectrum of possible climate change responses.

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Section: Discussionsupporting

confidence: 69%

Section: B Shelf and Deep Ocean Responsesupporting

confidence: 76%

Section: B Shelf and Deep Ocean Responsementioning

confidence: 97%

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Sensitivity of Antarctic Bottom Water to Changes in Surface Buoyancy Fluxes

et al. 2015

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“…°C yr -1 from 1991 through to 2006, after being relatively stable from 1972 to 1991 (Zenk and Morozov, 2007). In the Brazil Basin, the abyssal layers warmed by ~0.04 °C between 1989(Johnson and Doney, 2006.…”

Section: Introductionmentioning

confidence: 99%

Evolution of the Deep and Bottom Waters of the Scotia Sea, Southern Ocean, during 1995–2005*

et al. 2008

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“…A circulação abissal do Canal de Vemaé dominada pelaÁgua Antártica de Fundo (AAF; Antarctic Bottom Water, AABW A AAF, com temperaturas potenciais abaixo de 2 • C (correspondente a uma densidade ∼45,85 σ 4 ) nãoé uma massa d'água homogênea (Zenk & Morozov, 2007), podendo ser subdividida emÁgua Profunda do Mar de Weddell (APMW; Weddell Sea Deep Water, WSDW ), uma massa d'água mais densa encontrada junto ao fundo, eÁgua Circumpolar Inferior (ACI; Lower Circumpolar Deep Water, LCDW ) acima, sendo separadas pela isoterma de 0,2 • C. Logo acima, o fluxo dentro da camada ocupada pela APANé predominantemente dirigido para o sul com alguma influência da topografia. Hogg et al (1999) observaram que há um controle sobre a orientação e aceleração do fluxo sobre o Canal de Vema e a divisão do fluxo para oeste sobre uma depressão no Platô de São Paulo.…”

Section: Contexto Oceanográficounclassified

Potencial de transporte sedimentar pelas correntes de fundo na região do Canal de Vema (Atlântico Sul)

Kaji¹,

Guerra²,

Fernandes³

et al. 2011

Rev. Bras. Geof.

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ABSTRACT. Vema Channel is an important passageway to the flow of bottom water between the Argentine and the Brazil basins. The channel morphology causes confinement and intensification of bottom currents that affect the ocean floor through sediment resuspension, transport and deposition, consequently playing a fundamental role in the formation of deep ocean deposits. The main goal of this paper is to evaluate the potential for sediment suspension and transport by the local currents through estimates of nearbed shear stresses as well as to assess whether the present dynamic conditions are conducive to the buildup of contouritic deposits in the Vema channel area. The available datasets include (i) current velocity and direction from the World Ocean Circulation Experiment (WOCE) and from moorings deployed by the Woods Hole Oceanographic Institute (WHOI); (ii) hydrographic parameters from the World Ocean Database 2005; and (iii) the description of bottom sediment characteristics and nephelometric profiles available in publications such as research reports and scientific articles. Calculated shear stresses indicate that local currents would be able to erode and transport medium silt with density similar to that of quartz during up to 87% of the deployment duration, a finding that is reinforced by the nephelometric profiles and by suspended particulate matter concentrations documented by filtered water samples. Channel enlargement downstream leads to loss of transport capacity along the channel. These results suggest that a modern drift deposit may still be under construction downstream the channel mouth where a contourite fan has intermittently been built since the late Oligocene.Keywords: Vema Channel, shear velocity, benthic boundary layer, sediment transport. RESUMO. O Canal de Vemaé uma importante via de passagem daságuas de fundo da Bacia da Argentina para a Bacia do Brasil. A morfologia do canal causao confinamento e a intensificação das correntes de fundo que têm papel fundamental na ressuspensão, transporte e controle da deposição de sedimentos e consequentemente na formação de depósitos em profundidades abissais. O objetivo deste trabalhoé avaliar o potencial de ressuspensão e transporte de sedimentos pelas correntes locais através de estimativas do estresse cisalhante junto ao fundo para identificar condições de formação de depósitos contorníticos na região do Canal de Vema. Foram utilizados dados de (i) velocidade e direção das correntes provenientes da base de dados do World Ocean Circulation Experiment (WOCE) e de fundeios realizados pelo Woods Hole Oceanographic Institute (WHOI); (ii) características hidrográficas da região obtidas a partir da base de dados World Ocean Database 2005; e (iii) características granulométricas e perfis nefelométricos descritos na literatura. As estimativas do estresse cisalhante indicam que as correntes no canal são capazes de suspender e transportar silte médio com densidade similarà do quartzo durante até 87% do tempo. Essa capacidade de ressuspensão de sedimentos também ...

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Decadal warming of the coldest Antarctic Bottom Water flow through the Vema Channel

Cited by 73 publications

References 16 publications

Sensitivity of Antarctic Bottom Water to Changes in Surface Buoyancy Fluxes

Sensitivity of Antarctic Bottom Water to Changes in Surface Buoyancy Fluxes

Evolution of the Deep and Bottom Waters of the Scotia Sea, Southern Ocean, during 1995–2005*

Potencial de transporte sedimentar pelas correntes de fundo na região do Canal de Vema (Atlântico Sul)

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