Observational evidence for on-shelf heat transport driven by dense water export in the Weddell Sea

Darelius, Elin; Daae, Kjersti; Dundas, Vår; Fer, Ilker; Hellmer, Hartmut; Janout, Markus; Nicholls, Keith W.; Sallée, Jean‐Baptiste; Østerhus, Svein

doi:10.1038/s41467-023-36580-3

Cited by 11 publications

(14 citation statements)

References 34 publications

(60 reference statements)

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“…Finally, the strong spatial dependency between DSW export and the occurrence of the bottom‐intensified ASC implies the bottom‐intensification of the ASC could disappear if DSW formation weakens in a future climate with larger basal melt rates (Golledge et al., 2019; Li et al., 2023). This result has implications for climate predictions due to the importance of the bottom‐intensified continental slope sectors for onshore heat transport (A. L. Stewart & Thompson, 2015; Morrison et al., 2020; Darelius et al., 2023), ventilation of the abyssal ocean (Gordon et al., 2009), and carbon uptake (Gunn et al., 2023; Rae et al., 2018; Skinner et al., 2010). While our results indicate that the surface component of the ASC will not directly be impacted by changes in DSW export, larger basal melt rates may accelerate the surface ASC (Beadling et al., 2022; Moorman et al., 2020).…”

Section: Discussionmentioning

confidence: 99%

“…Such isopycnal connection between the continental shelf and the warmer offshore waters is of relevance as it provides a pathway for eddy‐driven onshore heat transport (A. L. Stewart & Thompson, 2015). Additionally, DSW overflows can invoke a barotropic pressure gradient across the submerged canyon and a return flow of CDW (Darelius et al., 2023; Morrison et al., 2020). The export of DSW itself occurs in geostrophic plumes that form gravity currents, which experience the Coriolis force, adjust accordingly, and generate a bottom‐intensified along‐slope flow that travels in the same direction as the surface ASC, and which is referred to as the bottom‐intensified ASC (Foldvik et al., 2004; Gill, 1973; Gordon et al., 2004; Huneke et al., 2022; Thompson & Heywood, 2008).…”

Section: Introductionmentioning

confidence: 99%

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Decoupling of the Surface and Bottom‐Intensified Antarctic Slope Current in Regions of Dense Shelf Water Export

Huneke,

Morrison,

Hogg

2023

Geophysical Research Letters

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The Antarctic Slope Current is guided by the topographic gradient of the Antarctic continental slope and creates a dynamical barrier between the continental shelf and the open ocean. The current's vertical structure varies around the continent affecting cross‐slope water mass exchange with consequences for Antarctic mass loss, ventilation of the deep ocean, and carbon uptake. The Antarctic Slope Current is surface‐intensified in many regions but bottom‐intensified in regions of dense overflows. This study investigates the role of dense overflows in modifying the dynamics of the bottom‐intensified flow using a 0.1° global ocean‐sea ice model. The occurrence of bottom‐intensification is tightly linked with dense overflows and bottom speeds correlate with dense overflows on interannual time scales. A lack of vertical connectivity between the bottom and surface flow, however, suggests that the along‐slope bottom water flows are coincidentally co‐located with the Antarctic Slope Current, rather than dynamically a part of the current.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Decoupling of the Surface and Bottom‐Intensified Antarctic Slope Current in Regions of Dense Shelf Water Export

Huneke,

Morrison,

Hogg

2023

Geophysical Research Letters

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“…When leaving the ice shelf cavity northward, the dynamics of the overflow of dense shelf water is strongly connected to southward transport of the relatively warm water, which triggers more basal melt in the ice cavity, as observed by a set of mooring placed at the continental shelf sill next to the Filchner Trough [ 60 ]. Ultimately, the northward-flowing (downslope) deep-water plumes form bottom water reservoirs, which ventilate the deep ocean via bottom ocean mixing, diffusing tracers throughout the deep ocean [ 27 ].…”

Section: Advances In Our Understanding Of Southern Ocean Carbon and H...mentioning

confidence: 99%

Southern ocean carbon and heat impact on climate

Sallée

Abrahamsen

Allaigre

et al. 2023

Phil. Trans. R. Soc. A.

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The Southern Ocean greatly contributes to the regulation of the global climate by controlling important heat and carbon exchanges between the atmosphere and the ocean. Rates of climate change on decadal timescales are therefore impacted by oceanic processes taking place in the Southern Ocean, yet too little is known about these processes. Limitations come both from the lack of observations in this extreme environment and its inherent sensitivity to intermittent processes at scales that are not well captured in current Earth system models. The Southern Ocean Carbon and Heat Impact on Climate programme was launched to address this knowledge gap, with the overall objective to understand and quantify variability of heat and carbon budgets in the Southern Ocean through an investigation of the key physical processes controlling exchanges between the atmosphere, ocean and sea ice using a combination of observational and modelling approaches. Here, we provide a brief overview of the programme, as well as a summary of some of the scientific progress achieved during its first half. Advances range from new evidence of the importance of specific processes in Southern Ocean ventilation rate (e.g. storm-induced turbulence, sea–ice meltwater fronts, wind-induced gyre circulation, dense shelf water formation and abyssal mixing) to refined descriptions of the physical changes currently ongoing in the Southern Ocean and of their link with global climate. This article is part of a discussion meeting issue ‘Heat and carbon uptake in the Southern Ocean: the state of the art and future priorities’.

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“…The outflowing SW lowers sea surface through geostrophic adjustment, and CDW is "pumped" poleward through the east side of these through. Recent observations also found evidence of onshore heat transport driven by dense water offshore export in the Weddell Sea (Darelius et al, 2023). Unlike the three-layer structure which is essentially forced by surface momentum flux, this process is driven by surface buoyancy flux shoreward of the shelf break edge.…”

mentioning

confidence: 96%

“…The work by Morrison et al (2020) and Darelius et al (2023) provided a new perspective to diagnose the cross-isobath transport under the influence of stratification and topography, however, their conceptual framework mainly applies to the troughs and do not directly diagnose cross-isobath transport over the shelf break edge. In this work, we extend the discussion of buoyancy-forced CDW intrusion mechanism to the Ross Sea continental shelf break.…”

mentioning

confidence: 99%

A Model Study of Buoyancy Driven Cross‐Isobath Transport Over the Ross Sea Continental Shelf Break

Wang,

Zhang,

Zhong

et al. 2024

JGR Oceans

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The intrusion of circumpolar deep water (CDW) onto the Antarctic continental shelf plays an important role in the heat budgets of the Antarctic shelf sea. In the Ross Sea, the Antarctic Slope Current is a strong vorticity barrier that prevents cross‐slope CDW exchange, yet observation evidence shows that CDW is able to get through this barrier in certain locations and reaches the edge of the Ross Ice Shelf (RIS). Previous studies often attribute the cross‐slope exchange to surface wind forcing, eddy and tide‐mediated fluxes. In this work, we highlight the role of buoyancy forcing from the continental shelf in the cross‐isobath exchange on the continental shelf break. The cross‐isobath transport along the Ross Sea continental shelf break is diagnosed with the depth‐averaged vorticity budget equation, using results from an ice‐ocean coupled numerical model. Our results show that the leading‐order balance of vorticity is between the advection of planetary vorticity and the joint effect of baroclinicity and relief (JEBAR). The JEBAR effect supplies negative vorticity and drives onshore transport over the eastern Ross Sea. The heterogeneous transport over eastern and western Ross Sea results in a zonal sea level gradient, with higher sea level over the eastern Ross Sea. The magnitude of JEBAR is determined by horizontal density gradient along the Ross Sea shelf break edge; numerical tracer experiments suggest that the along‐isobath density gradient is set up by the dense shelf water formed over the RIS and the inflow of glacial basal melt water from the Amundsen Sea.

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Observational evidence for on-shelf heat transport driven by dense water export in the Weddell Sea

Cited by 11 publications

References 34 publications

Decoupling of the Surface and Bottom‐Intensified Antarctic Slope Current in Regions of Dense Shelf Water Export

Decoupling of the Surface and Bottom‐Intensified Antarctic Slope Current in Regions of Dense Shelf Water Export

Southern ocean carbon and heat impact on climate

A Model Study of Buoyancy Driven Cross‐Isobath Transport Over the Ross Sea Continental Shelf Break

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